Continental Shelf Research 57 (2013) 105–116

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From food to feed: Assessment of the stationary lift net fishery ofEast Hainan, Northern South China Sea

Uwe Krumme a,b,n, Tian C. Wang a, Dao R. Wang c

a Leibniz Center for Tropical Marine Ecology (ZMT), Fahrenheitstr. 6, 28359 Bremen, Germanyb Institute of Baltic Sea Fisheries, Johann Heinrich von Thunen-Institute (vTI), Federal Research Institute for Rural Areas, Forestry and Fisheries,

Alter Hafen Sud 2, 18069 Rostock, Germanyc Hainan Provincial Marine Development Plan and Design Research Institute, 14th floor, Zhonghang building, 15 Longkun Bei Road,

Haikou 570203, Hainan, PR China

a r t i c l e i n f o

Article history:

Received 25 March 2011

Received in revised form

10 March 2012

Accepted 18 April 2012Available online 27 April 2012

Keywords:

Lift net

By-Catch

Discard

Low value/trash fish

Artisanal fishing methods

Small-scale fisheries

43/$ - see front matter & 2012 Elsevier Ltd. A

x.doi.org/10.1016/j.csr.2012.04.011

esponding author at: Institute of Baltic Sea Fi

-Institute (vTI), Federal Research Institute fo

s, Alter Hafen Sud 2, 18069 Rostock, Germ

9 381 8116199.

ail address: uwe.krumme@vti.bund.de (U. Kru

a b s t r a c t

In the Asia-Pacific region, the increasing demand for low value/trash fish as feed for mariculture drives

unsustainable fisheries on already overexploited marine resources. The mariculture demand may also

affect artisanal nearshore fisheries operating in shallow nursery grounds, e.g., lift net fisheries, but little

is known about how they work. We describe the stationary lift net artisanal fishery on the East coast of

Hainan Island (northern South China Sea). A trapezoidal blanket net (mean surface area: 478 m2),

stretched between four upright poles at the corners, is lowered and lifted via a rope system from a

tower by a single fisher. In 2009 �200 households depended on 288 lift nets, 82% of which were

located in the Wenchang/Wenjiao estuary. The number of lift nets decreased by 15% from 2007 to 2009.

Presently, it is mainly an early retirement activity of fishers with a median age of 52 years and younger

men rarely enter the fishery due to low catch rates. However, not one fisher would stop fishing even at

50% hypothetical decline in catch — due to lack of alternatives. Mean catch weight per fishing day is

12 kg (range: 0–1.7 t). In the past, the entire catch was used as food. Presently, an average of 52% of the

catch is sold as feed to local pond and floating net cage mariculturists who, subsequently, supply the

live food trade to markets as far as Hong Kong. Larger dead fishes are sold at village markets or at

Qinglan harbor and are locally or regionally consumed. The density of lift-net operation is highest

around the Wenchang/Wenjiao lagoon due to the presence of an extensive sheltered, shallow subtidal

area in proximity to mariculture and export markets in Qinglan. Thus, the modern mariculture demand

for low value/trash fish supports the continuation of an ancient artisanal fishery despite severe resource

depletion. The existence of similar lift nets in Vietnam points to an exchange in the artisanal fishing

knowledge between Vietnam and Hainan. Additionally, interviews with lift-net fishers provided

valuable information on historical changes in the lagoon system (e.g., mangrove loss, sedimentation,

pollution, interaction with other fishing activities), and suggest that the summer fishing moratorium of

the offshore fleet leads to increased fishing pressure on inshore resources by artisanal fisheries.

In conclusion, we provide suggestions for management of the inshore water resources and their

artisanal fisheries.

& 2012 Elsevier Ltd. All rights reserved.

1. Introduction

In many parts of the Asia-Pacific region the coastal fisheriesresources are subject to overexploitation (Silvestre et al., 2003;Stobutzki et al., 2006). In Chinese waters, most fisheries resourcesare experiencing both growth and recruitment overfishing andthe proportion of species of low trophic level and of immature fish

ll rights reserved.

sheries, Johann Heinrich von

r Rural Areas, Forestry and

any. Tel.: þ49 381 8116148;

mme).

in the landings has increased (Chen, 1999; Cheung and Sadovy2004; Cheung and Pitcher, 2008). As a consequence, in manycountries the development of coastal mariculture has beenencouraged to provide protein, income, employment and exportearnings. This, in turn, leads to an increasing demand for lowvalue/trash fish for use as feed, and is mainly provided by marinecapture fisheries (FAO, 2005; Staples and Funge-Smith, 2005;Chau and Sadovy, 2005). In the East China Sea the proportion oflow value/trash fish sometimes constitutes far more than 50% ofthe landings of the marine capture fishery (Grainger et al., 2007).However, the processing industry is often underdeveloped(Li et al., 2009). The use of low value/trash fish as fish feed leadsto enormous nutrient input into the surrounding waters from the

Fig. 1. Study area on the East coast of Hainan Island (a). Division into seven coastal sectors (b), and eight subsectors in the Wenchang/Wenjiao estuary (sector 2) with an

inset of the floating net cage area in front of Qinglan harbor (c); for sector and subsector names refer to Table 1.

U. Krumme et al. / Continental Shelf Research 57 (2013) 105–116106

mariculture facilities (e.g., Leung et al., 1999; Wu et al., 1999; Xuet al., 2007). This activity often employs floating net cages whereimmature wild-caught fishes are kept for grow-out and then soldin the live food trade. The removal of immature wild-caughtfishes, especially reef fishes such as groupers, moray eels orwrasses, for use in the live food trade contributes to overexploita-tion of source populations (Sadovy and Vincent, 2002).

Moreover, the demand for low value/trash fish from themariculture drives unsustainable fisheries on overexploited mar-ine resources and leads to growth overfishing of the fish stocksused as feed (Soliman and Yamaoka, 2010). Growth overfishingoccurs when too many small fish are caught too early so thatthe fish are not given enough time to grow to the optimum size.A dangerous feedback loop of ever-increasing fishing pressure,due to the growth of restaurants, live fish trade, and inshore andoffshore feed fisheries, is underway in the Asian-Pacific regionwith yet unclear economic, social and ecological consequences(FAO, 2005; Staples and Funge-Smith, 2005; Funge-Smith et al.,2005; Chau and Sadovy, 2005). Little information is availableabout the marine fishery involved in low value/trash fish land-ings, e.g., on species or sizes (FAO, 2005; but see Chau and Sadovy(2005). Nearshore artisanal fisheries may contribute and respondto the variable supply of low value/trash fish by the marinecapture fisheries but even less is known about these small-scalefisheries. Stationary lift net fisheries are particularly likely tosupply the low value/trash fish market because they operate withsmall mesh sizes in overfished nearshore coastal habitats andtherefore target mostly small-sized nektonic organisms in shal-low nursery grounds.

The major management measure in China for the marinecapture fisheries beyond the ‘‘closed line’’, i.e., the offshore area(Chen, 1999) is a fishing moratorium during two summer months,yet it has been insufficient in aiding the recovery of the depletedresources (Cheung and Pitcher, 2006; Jiang et al., 2009; Shih et al.,2009). The provincial fisheries administration is responsible forthe fisheries management in inshore waters (Chen, 1999). Mostinshore fisheries are also depleted, due in part to poor provincialfunding and implementation of existing laws (Chen, 1999; Chenget al., 2006). A link exists between the offshore and inshore

fisheries in that the summer offshore fishing moratorium forcessome additional fishing effort inshore. The consequences of thisincreased effort on low value/trash fish supply and prices are yetunclear.

On the East coast of Hainan Island, northern South China Sea,large stationary lift nets are a conspicuous feature of shelteredshallow areas. In particular, the Wenchang/Wenjiao estuary ischaracterized by an extraordinary high abundance of these nets,so that the central lagoon partly resembles a lift net park (Fig. 1,Supplement 1a). Despite this conspicuity, virtually nothing isknown about this kind of fishery and the design of these lift nets.

The lift net is an ancient artisanal fishing gear (von Brandt, 1975;von Brandt et al., 2005), which is set horizontally below the watersurface and quickly lifted once nektonic target species are swim-ming above it. Different types of stationary lift nets have beendeveloped for use in freshwater and coastal environments of Asia,Europe and Africa (von Brandt et al., 2005). A large variety of lift netsis used along the coasts of South-East Asia, e.g., in Thailand(Boromthanarat et al., 1991; Islam and Ikejima, 2010), Vietnam(Ton That Phap, 2000), Malaysia (von Brandt et al., 2005), Indonesia(Dudley and Tampubolon, 1986; van Oostenbrugge et al., 2002), thePhilippines (Selorio et al., 2008) and China (Osaka, 1975).

The drawings in Osaka (1975) show a large inland lift net thatis operated via two reels at the corners of one side and two fixedpoles at the corners of the other side. This design, however, differssubstantially from the design in Hainan.

The well-known ‘‘Chinese lift nets’’ on the coast of Kerala, India(e.g., in Kochi) which work with a cantilever and counterweightsare apparently Chinese in origin and were either introduceddirectly by the Chinese in the 15th century or by the Portuguese(von Brandt et al., 2005, see also Osaka (1975)). Mainland Chinaseems to have a rich history of lift net fishing (Osaka, 1975; vonBrandt, 1975), but due to rapid economic development, manyartisanal subsistence fishing methods, and the biological knowl-edge on natural resource dynamics that they yield, have beendisappearing. This trend has also been observed in other parts ofthe Indo-West Pacific, e.g., Papua New Guinea (Johannes, 1984).This is in part due to these methods being viewed by youngpeople as comparably inefficient, labor-intensive or antiquated.

U. Krumme et al. / Continental Shelf Research 57 (2013) 105–116 107

The purpose of this study is to conduct the first comprehensiveassessment of the stationary lift net fishery in East Hainan usingfield surveys, interviews, experimental nekton sampling, andsatellite image analysis. It presents spatio-temporal patterns inlift net distribution, and technical, socio-economic, ecological,marketing and historical aspects of the lift net fishery. Fourspecific questions were posed: (1) How does the distribution oflift nets vary in space and time, and do net dimensions differamong sites? (2) How does the lift net fishery work today ascompared to the past? (3) Would fishers stop fishing underhypothetical scenarios of declining catches? (4) Does the food:-feed ratio of the catches differ among estuarine salinity zones?We discuss the status of the lift net fishery and derive implica-tions for the management of the artisanal shallow-water fisheriesin the region.

2. Study area

The study area comprised a coastal stretch of �70 km alongthe east coast of Hainan from Tongguling at the north-eastern-most tip of Hainan to the Wanquan River lagoon near Boao in thesouth (Fig. 1(A) and (B)). Five fringing reef segments (substratum:sand and coral rubble) occur in two seascape settings in the area:(i) back-reef areas of a few 100 m width (Tongguling to Yelin; seesector 1 in Fig. 1(B)), and (ii) back-reef areas of 41 km width(Changqi, Fengjiawan, Qingge, Tanmen; see coastal sectors 3, 4, 5,6 in Fig. 1(B); Table 1). Water depths at low tide range between0.5 and 1.5 m. The Wenchang/Wenjiao estuary consists of ashallow kidney-shaped lagoon (Bamen Bay) which is connectedto the sea via a narrow inlet channel (Fig. 1(C)). The major part ofthe lagoon is 2–4 m deep at low tide (Fig. 1Cf). The substratum ismainly muddy in the upper and muddy–sandy in the lowerreaches, with patches of interspersed rock. Qinglan and Tanmenare the largest harbors in the area (Fig. 1(B)). Numerous shrimpand fish ponds in former mangrove areas and along the coast are amajor source of untreated effluents (Krumme, Herbeck and Wang,unpublished data; Herbeck et al., 2011). Mariculture with floatingnet cages covering 4.8 ha has been established in front of Qinglanharbor and at the mouth of the inlet channel (Fig. 1Ce, (f);Supplement 1g; Krumme, Herbeck and Wang, unpublished data).Tourist resorts exist at Tongguling (Fig. 1(B), sector 1), Gaolongwanand Yelin (Fig. 1Cg, (h)). Typhoons regularly affect the East coast of

Table 1Annual changes in the number of operational lift nets in coastal sectors and subsector

Coastal sectors Subsecto

1 Tongguling to Yelin

2 Wenchang/Wenjiao estuary

a Wenchan

b Bamen B

c Wenjiao

d North of

e Qinglan

f Inlet cha

g Gaolongw

h Yelin

3 Changqi

4 Fengjiawan

5 Qingge

6 Tanmen

7 Boao lagoon and adjacent coast

Total sum

a The numbers of the Wenchang/Wenjiao estuary are the yearly sums from the sub Field census in March/April 2009 like in 2007 and 2008.c Census of lift nets visible on Geoeye-1 GEO PSM 4-bands image from September

Hainan during the hot and wet summer monsoon (May toSeptember). During the winter monsoon (October to April) it iscooler and dryer. Mixed semidiurnal tides have a maximum tidalrange of about 2 m.

3. Materials and methods

3.1. Census of lift nets

The distribution of lift nets in the study area was surveyed inAugust/September 2007, June/July 2008 and March/April 2009. TheGPS position of each operational lift net was recorded. In the field liftnets were classified as operational when their accompanying netswere intact and without fault or, when tower and poles withanchoring ropes were intact but the net had obviously beenremoved for repair. The study area was divided into seven coastalsectors, and the numbers of lift nets within each sector was summedup for each year. The sector Wenchang/Wenjiao estuary was furtherdivided into eight subsectors (Fig. 1(B) and (C); Table 1).

To explore the usefulness of satellite image analysis in remotelift net surveys, we counted the lift nets visible on a Geoeyesatellite image (GEO PSM 4-bands from September 22, 2009) thatcovered the coastal area from Tongguling to Qingge. The lift netsidentified on the satellite image were used to determine thesurface area of the nets and the length of the ropes between thetower and the front poles using GIS. In the field site-specificdifferences in lift net dimensions were conspicuous so that weused Kruskal–Wallis tests to assess whether two parameters withobvious inter-site patterns (the area of the nets, and the length ofthe ropes between the tower and the front poles) differedsignificantly among six subsectors (Wenchang River, WenjiaoRiver, Bamen Bay, north of Qinglan, Qinglan harborþ inlet chan-nel, and back-reef area (Tongguling to YelinþYelin); Fig. 1).We used the Nemenyi test for post-hoc comparison with ao0.01.

3.2. Interviews

Semi-structured interviews were carried out with 18 lift netfishers in August/September 2007 and March/April 2009, e.g., onthe design of the nets, and the history, status and future of thefishery. In addition, more detailed and structured interviews werecarried out with 10 of these 18 lift net fishers in March/April

s on the East coast of Hainan.

ra Year

2007 2008 2009b 2009c

44 45 45 8

289 268 236 166

g River 13 18 13 8

ay 96 99 98 75

River 15 14 6 12

Qinglan 98 88 74 52

harbor 9 10 3 2

nnel 24 22 22 10

an 21 4 6 0

13 13 14 7

2 2 1 (þ3n) 1 (þ3n)

0 0 0 (þ2n) 0 (þ2n)

0 0 0 (þ1n) n.c.

8 11 5 n.c.

0 0 0 n.c.

343 326 293 180

bsectors a–h. See Fig. 1 for sector and subsector boundaries.

22, 2009 with 0.6 m resolution; nlift nets in artificial channels; n.c.: no coverage.

Fig. 3. Satellite view of a lift net in the Wenjiao River, taken from Geoeye-1 GEO

PSM 4-bands image from September 22, 2009 with 0.6 m resolution. Approximate

lengths of net sides: a: 21.6 m; b: 21.7 m, c: 26.9 m, d: 21.6 m. Ropes difficult to

see but indicated using abbreviations from Fig. 2; length of 1l: 34.9 m; 1r: 33.7 m.

U. Krumme et al. / Continental Shelf Research 57 (2013) 105–116108

2009. Each interview lasted about 1 h. Two fishers were from theriver (Fig. 1Ca), five from the lagoon (Fig. 1Cb, (d)) and three fromthe back-reef area (Fig. 1Cg, (h)) of the Wenchang/Wenjiaoestuary, covering the three major coastal habitat types where liftnets occur. We used a qualitative approach because it is wellsuited to elucidate complex activities at the micro-level, espe-cially when the fishery and related livelihoods are not known.

The structured interviews covered personal background infor-mation (age, education, job history, family), household economy(properties, income from the fishery and alternative incomes,importance of subsidies, borrowing), way of fishing (fishing times,soak time, target species, catch amounts), marketing channels,sales and prices (transport of catches, sales prices, point of sale,use of catches, buyers), historical changes in catch composition(catch amount, species changes), response to a hypotheticaldecrease in catches of 10%, 20%, 30% and 50% (following Cinneret al., 2008), major problems of the fishing as perceived by thefishers, and how their situation could be improved.

We used an album with 4�7 cm color photographs of 51major nektonic species, which were taken from local specimensduring scientific lift net samplings in the study area (see below),to obtain information on species or taxonomic group levels.Questions had been prepared in German and were translated intostandard Mandarin. Interviews were carried out by U.K. andT.C.W. In case of two older fishers, questions were translated intoHainanese. Most interviews were carried out in teahouses or inthe fishers’ homes. If not indicated otherwise, we refer to theresults from the structured interviews with 10 fishers.

Finally, we used semi-structured interviews with a middlemanand a fish drier in Qinglan to better understand the fate of the liftnet catches and the marketing chain of the artisanal fisherieslandings. Prices are given in renmenbi (RMB).

3.3. Experimental fish sampling

We used a standardized sampling regime to assess the fishcommunity in the area, given differing methods between indivi-dual fishers. The main sampling standardizations were the lack oflight attraction at night and a short and fixed soak time. While ourmethod may not exactly mimic the catches of the lift net fishery,the results were used to estimate the proportion of fisherycatches used for consumption (food) and as low value/trash fish(feed). Standardized lift net catches were carried out in July/August 2007, June/July 2008 and March/April 2009 at a fixedupper, middle and outer estuarine site without artificial light(Fig. 1(C)). In each year, sites were sampled during two 24-hperiods during a spring tide cycle. Each 24-h cycle was dividedinto eight 3-h intervals. At the beginning of each interval, twoadjacent lift nets simultaneously took three consecutive sampleswith 20 min soak time for each haul. Each individual nektonicorganism was identified, measured and weighed and its use was

Fig. 2. Side view of a Hainanese lift net at Yelin beach at low tide. T: tower at the beach;

horizontal net with front part slightly lower than rear part; 2: left and right anchoring

poles; 4: left and right rearward anchoring rope (4l, 4r) of the rear poles. Note backwar

and lifting of the net via the ropes 1l and 1r.

assigned to ‘‘consumption’’ (when 410 cm total length or40.5 kg weight) or ‘‘low value/trash fish’’ for smaller individuals.This classification is based on information gained during theinterviews with the lift net fishers and was verified duringsurveys on local markets. A food:feed ratio was calculated forthe total catch of each 24 h cycle.

It should be noted that our estimates are subject to unknownbias. We did not cover winter months; lower winter fish abundancesand species richness would likely result in lower quantitativeestimates and changed species compositions. On the other hand,light is used to attract fishes so that our standardized catches arelikely underestimates of the true amounts removed at night in themiddle and upper estuary; and it is not known if artificial lightsignificantly changes the lift net catch composition at night.

4. Results and discussion

The Hainanese name of the lift net is gadan. The most commonname in standard Mandarin is q�ıngshanwang (green hills net), butd�ıngz�ıwang (name of a character that resembles the form of thelift net) and s�ıjıaowang (quadrangular net) are also used.

The Hainanese lift net is an ingenious stationary fishingmethod consisting of a huge trapeziform non-framed horizontal

1: left (1l) and right (1r) rope connecting front poles with the reel in the tower; N:

rope (2l, 2r) of the front poles; 3: left and right anchoring rope (3l, 3r) of the rear

d inclination of the poles in the resting position which ensures controlled lowering

Fig. 4. Lowering of a lift net (A)–(C). Front-right pole with rope 1r in the foreground (p). The base of the pole is the breakover point. The pole is tilt backwards and slightly

sidewards, thereby laying the net on the ground. Note the V-shaped bottom rope (v) at the base of the pole whose ends are fixed by a wooden ground stake (s1, s2); it keeps

the base of the pole in place (only shown in (A)).

U. Krumme et al. / Continental Shelf Research 57 (2013) 105–116 109

net which is stretched at the corners by poles (Figs. 2 and 3).The poles – together with the net – are lowered and lifted via arope system by a single fisher sitting behind a reel on a tower (seevideo/Supplement 2).

Supplementary material related to this article can be foundonline at http://dx.doi.org/10.1016/j.csr.2012.04.011.

In the resting position the net is lifted, i.e., fully above thewater surface. The poles are slightly inclined backwards whenseen from the tower (ca. 801). Four pairs of ropes stretch the net:Each front pole of the net is connected to a tower via a rope of10–23 m length which is wound up on the reel (pair 1; 1l and 1rin Figs. 2 and 3). Anchoring ropes on the front poles (length:�40 m) and rear poles (length: �47 m) stretch the net on thetransversal axis (pairs 2 and 3; 2l and 2r, and 3l and 3r inFigs. 2 and 3). The rearward anchoring ropes (length: �12 m)ensure the backward inclination of the poles (pair 4; 4l and 4r inFigs. 2 and 3). The ropes on the reel (pair 1) act as counterforce tothe weight of the net on the longitudinal axis. When unrolling thereel, the poles tilt back until the net lays on the ground (Fig. 4).While lifting the net (which takes o45 s), its edges rise first. Thenektonic organisms tend to escape towards the deeper center ofthe net so that only fishes close to the net edges and fast surfaceaccelerators (e.g., large Mugilidae) are capable of escaping. Thecentral section of the net usually has a smaller mesh size thanthe margins to hinder entangling of the fishes. To collect a haul,the fisher puts the net into the resting position, climbs down thetower and moves to a side of the net with a boat or a styrofoamraft. There he shakes the net to concentrate the nektonic organ-isms at its lowest point and collects them with a scoop at the endof a long bamboo (see video/Supplement 2).

4.1. Spatial distribution and dimensions of lift nets

The large-scale survey of lift nets showed that the Wenchang/Wenjiao estuary is the center of the lift net distribution along theEast coast of Hainan, particularly the shallow and shelteredsubtidal lagoon areas b and d (Fig. 1(C)), with on average 82% ofall lift nets in the area (Table 1, Supplement 1a). The East coastappears to house the major concentration of lift nets in Hainanprovince. At least five lift nets were counted in Dongzhai Bay andonly three in the lower reaches of the Nandu River near Haikou(north Hainan), but sporadic visits to other coastal sites on thenorth-east, south-east and south coast revealed no further liftnets (beaches north of Tongguling, south of Boao, Xincun, fromSanya westwards to Yinggehai), most likely due to the presence ofrelatively steep, rocky or sandy shorelines and lack of extensiveshallow bays.

The surface area of the nets (mean7SD: 478 m2777, n¼166)did not differ significantly among subsectors of the Wenchang/

Wenjiao estuary (Kruskal–Wallis test, Chi-Square¼8.67, df¼6,p¼0.19), but the largest nets were found in the inlet channel,Bamen Bay and in the lagoon north of Qinglan (means persubsector: 530, 489, and 475 m2, respectively).

The length of the rope between the tower and the front poles(pair 1; Figs. 2 and 3) differed among subsectors (Kruskal–Wallistest, Chi-Square¼18.97, df¼6 p¼0.004), with significantlyshorter ropes in the back-reef area (mean7SE: 18.2 m71.3)and in the inlet channel (mean7SE: 21.8 m70.9) than in BamenBay, north of Qinglan and the Wenjiao River subsectors (meansfrom 25.9 to 29.6 m) (po0.001).

Differences in lift net dimensions reflected site-specific adap-tations to the local habitat and in catching method. In the back-reef area the shorter rope lengths between tower and front poleswere likely an adaptation to the visual capture of Mugilidae atdaylight (see 4.7). In the inlet channel (where fishers work mainlyat night) this may mainly be a response to the limited shallowarea at the channel edge and the need to stay away from the routeof fisher boats.

4.2. Temporal changes in the number of lift nets

Regarding longer-term changes, the fishers from the lagoonand the back-reef area reported an overall increase in the numberof lift nets over the past decades. In contrast, fishers at the riverarea said that the number of lift nets has been decreasing in thepast decade.

From 2007 to 2009 the total number of lift nets in the study areadecreased by 50, i.e., a decline by 15% with reference to 2007. Thiswas mainly due to a decline in the four subsectors c, d, e and g of theWenchang/Wenjiao estuary (Table 1). On the satellite image fromlate summer 2009 only 61% of the lift nets counted during our fieldsurvey in spring 2009 were re-identified from satellite photos despitetheir high resolution (Table 1). This suggests that the field surveysare indispensable for the census of lift nets and that remote sensingmay inadequately identify the nets, poles, ropes and towers (espe-cially those without a roof) given their low light reflectance andcontrast against the water and coast. Field surveys do not onlyprovide more precise distributional data and information on theactivity status of the nets (even when the net is removed for repair)but are also much more cost-effective for monitoring purposes, giventhat it takes a person 4 days to survey the study area while a Geoeyeimage costs 42000 Euros. On the other hand, once lift nets areidentified on a satellite image their dimensions can be measuredwith great ease and high accuracy.

Photo and field evidence from colleagues gave rise to twoadditional results: (1) Stationary lift nets virtually identical inconstruction to those in Hainan exist in Nha Trang, Vietnam. InVietnam, some lift nets may have an opening in the center of the

U. Krumme et al. / Continental Shelf Research 57 (2013) 105–116110

net so that the catch can be directly released into the boat (noscoop net necessary). Unfortunately, except for a contribution ofTon That Phap (2000) we did not find a single study published inEnglish analyzing the stationary lift net fishery in Vietnam. (2) Asearch for lift nets on Google Earth (accessed in March 2011)along the coast of Vietnam showed that lift nets of the same typeas those in Hainan are widespread in lagoons and estuaries alongthe central Vietnamese coast at least from the Quang Binhprovince in the north to the Khanh Hoa province in the south.This emphasizes that the most appropriate sites for stationary liftnet fisheries are lagoons and bays with extensive sheltered,shallow subtidal area. Given the exact match in lift net construc-tion, similar coastal settings and widespread use in Vietnam, wehypothesize a close link and exchange in the artisanal fishingknowledge between Vietnam and Hainan. There are linguisticrelationships between aboriginal tribes in Hainan and Vietnam(e.g., Thurgood, 1999) and the colonization of Hainan by Hanpeople from mainland China was relatively recent (Li et al., 2008),mainly from the Guangxi, Guangdong and Fujian province.Furthermore, the colonizers from south China are unlikely tohave introduced the lift nets to Hainan because the south Chinacoastline is poorly suited for extensive lift net operation due tofew sheltered estuarine lagoons. Another search with GoogleEarth (accessed in March 2011) yielded only four isolated liftnets along the coast of the Guangdong province and one smallarea with Z16 lift nets on the coast of the Fujian province.

4.3. Estimate of the number of lift net fishers

The number of lift nets does not automatically reflect thenumber of fishers. Five interviewees owned one and the other fiveowned two lift nets (i.e., on average 1.5 nets per fisher). A fishercan operate two adjacent lift nets simultaneously; or given site-specificity in catches, he can use one lift net as an alternativewhen the catches at the other lift net site are low. Using the 2009total of 288 lift nets in the area (Table 1) as a reference and1.5 nets per fisher, we estimate that about 200 families maydepend partially or fully on the lift net fishery (288 nets/1.5¼192fishers). According to this approximation, the interviewees

Fig. 5. View from a lift net tower towards the fringing reef at Yelin beach. (A) r: reel wi

go in parallel onto the reel r; pr: pair rods (pr1, pr2) and a single rod (sr) to turn the ree

(r) with notch (n) and guide piece (g).

represented about 5% of the lift net fishers in the area. About80–100 lift net fishers, i.e., around half of the estimated total, livein the village Shahou (Fig. 1(C)). This is the largest concentrationof lift net fishers in the area. They dominate the lift net fishery ofthe subsectors b and d. They were the first to occupy the goodfishing places, which are passed on from father to son. The lift netfishers of the other subsectors and sectors are scattered in villagesalong the estuary and the coast and live at a maximum distancefrom their lift net of 20 min by bicycle or motorcycle.

4.4. Personal background

61% of the fishers were 46–56 years old, 22% were 63–74 yearsand only 17% were 23–35 years old (n¼18). All respondents weremen. 60% of them had completed secondary school, others onlyprimary school and the oldest fishers had never attended school.All but one of the interviewees have always worked as fishers inthe area; the exception was previously a migrant worker in WestHainan. 50% had lift net experience for 14–50 years (mean: 33years) while the other 50% had fished with lift nets for 2–8 years(mean: 4 years) (n¼18). All interviewees have been operatingtheir lift net(s) at the same site since they started as lift net fisher.The lift net fishery has existed for 4100 years in the region, butnot one fisher could report on the origin of this fishing technique.Most of them had learned the use of lift nets from their father,rarely from neighbors. All older men considered their work anearly retirement activity. They opted for the lift net fisherybecause it is less labor-intensive and dangerous than theirprevious activities and ensures that they are able to continue toenjoy fishing and nature. The few younger fishers only opted forthe lift net fishery because they were unable to find a better, i.e.,higher-income job.

4.5. Household economy

The fishers belong to the working class. There were only smalldifferences in the standard of living among the fishers. Everyrespondent owned a boat, motorcycle, house, and a TV. The meanmonthly income from the lift net fishery was 1500 RMB and

th furled ropes 1l and 1r which are connected by a cross-rope (cr) so that 1l and 1r

l r; L: rope for locking the net in the resting position at sr. (B) Right end of the reel

U. Krumme et al. / Continental Shelf Research 57 (2013) 105–116 111

ranged between 100 and 3000 RMB, but respondents mentionedthat 7000 RMB could be reached at the best fishing locations(during the time of sampling, 10 RMB were �1 Euro). Since fishesare not homogenously distributed, the yields of a fixed fishingmethod vary with location, and the best places have beenoccupied in the past.

Five of the interviewees worked full-time as lift net fishers.Three fisher earned additional income by fishing in the lagoonwith trammel nets, one offshore with hook-and-line and one bycollecting invertebrates in the mangrove. Four of them also had asmall field for cash crop cultivation, and two received moneyfrom their children. Three of the fishers received subsidies of onaverage 200 RMB per year. All fisher had saved money topurchase a lift net or had built it themselves. Not one fisher usedcredit and no client-patron dependencies exist.

4.6. Construction and mode of operation

There are no restrictions for newcomers in the lift net fishery,but they are expected to consult with nearby net owners and to

Table 2Scientific and Hainanese names, relative abundance, use, and mean prices of major nekt

Hainan. Hainanese is not a written language and local names are given in phonetic trans

rare but with high demand (r). Mean prices: Prices refer to information from one to eig

large fish (40.5 kg), respectively.

No. Nektonic group Family Name of organism

Scientific Hainanes

1 Fish Clupeidae Clupanodon thrissa huang yu

2 Fish Clupeidae Sardinella gibbosa qi�e lan

3 Fish Gobiidae Gobiid speciesb gao bo

4 Fish Ambassidae Ambassis spp.b shan ya

5 Fish Synodontidae Trachinocephalus myops gao da�ı

6 Fish Engraulidae Thryssa spp.b am dui

7 Fish Atherinidae Atherinomorus lacunosus ba la �o

8 Fish Leiognathidae Leiognathus spp.b l �u gia

9 Fish Mugilidae Mugil cephalus j�ıang hao

10 Fish Gerreidae Gerres filamentosus hai j�ı

11 Fish Siganidae Siganus canaliculatus lou y �ue g

12 Fish Mugilidae Valamugil perusii d�ai g�ıa

13 Fish Engraulidae Stolephorus indicus d�ı gang

14 Fish Scatophagidae Scatophagus argus dong gou

15 Fish Siganidae Siganus guttatus h�ıa jiao

16 Fish Sparidae Acanthopargus berda lab la

17 Fish Sillaginidae Sillago aeolus du�a du�ı

18 Fish Lutjanidae Lutjanus argentimaculatus x�ıa dia

19 Fish Haemulidae Diagramma picta ga j�ı

20 Fish Plotosidae Plotosus lineatus d�a mo

21 Fish Terapontidae Terapon jarbua ba�ı gou

22 Fish Hemiramphidae Hyporamphus limbatus g �ui jiam

23 Fish Carangidae Caranx ignobilis d %ung

24 Fish Carangidae Scomberoides lysan gou lın d

25 Fish Clupeidae Escualosa thoracata q�ıng l�an b

26 Fish Cynoglossidae Cynoglossus puncticeps lang j�ı

27 Fish Latidae Lates calcarifer g�ım d %uo

28 Fish Lutjanidae Lutjanus russellii ogı

29 Fish Monacanthidae Monacanthus chinensis d�ıng de m

30 Fish Mullidae Upeneus tragula ba ka

31 Fish Ophichthidae Pisodonophis cancrivorus su�a

32 Fish Sciaenidae Dendrophysa russelli ang yuei

33 Fish Serranidae Epinephelus bleekeri g �ou yu

34 Fish Soleidae Brachirus orientalis gao jı

35 Fish Sphyraenidae Sphyraena fosteri sh �ui gia

36 Fish Tetraodontidae Takifugu oblongus bao g �ui

37 Ray Dasyatidae Dasyatis spp. ang

38 Shrimp Penaeidae hei

39 Crab Portunidae Portunus pelagicus hui

40 Mantis shrimp Squillidae Oratosquilla oratoria gou jia

41 Horseshoe crab Limulidae Carcinoscorpius rotundicauda ao

a Other fish species used as supplementary feed are Elops hawaiensis, Megalops cypb Ambassid, Gobiid, Leiognathid and Thryssa species were not further identified in

keep navigation channels free. The lift net fishers have no specificlicense. They are neither part of a specific association nor are theyinstitutionally represented in any stakeholder organization. Theyare not aware of any management measures that would restricttheir fishing activity.

The construction of a lift net requires four men, a sledgehammer,a saw, a drill, ropes and a knife, and takes about a week. First, thetower is built, and then the net with the ropes is assembled. For thetower, four poles (�12 cm diameter each) are driven into thesediment at the corners of a square of approximately 2.3 m on aside (Figs. 2 and 5) by two men using an auxiliary cross beam. Fourlevels of cross beams are moored with ropes (�0.6 m between eachlevel) and form the bracing. They allow climbing the tower toconstruct the seat (at �4 m above low-water level) with the reeland, optionally, the roof. The reel (�15–20 cm diameter) is slightlylonger than the tower is wide. Guide pieces prevent the reel fromrolling ahead. To turn the reel with the hands and feet against thegravitational force of the net, two pairs of rods and a single rod(�3 cm diameter) are passed through holes in the center of the reel,each shifted by 601. The paired rods are tied together at the ends.

onic organisms captured by lift net fishers in the Wenchang/Wenjiao estuary, East

cription. Relative abundance (RA): Fishers distinguished between common (c), and

ht fishers in spring 2009. Small/Large: Prices for small (o10 cm total length) and

RA Usea Price (RMB kg-1) Small Large

e Standard

c Feed 4

c Feed 3

c Feed 3

c Feed 2.5

Feed 2

Feed

c Feed/consumption 2

c Feed/consumption 2 45

c Feed/consumption 3.8 36

c Feed/consumption 3 35�ıa c Feed/consumption 3 22.5

c Feed/consumption 2.5 16

c Dry fish/feed 13

r Consumption 120

Consumption 50

Consumption 50

Consumption 31

Consumption 30

Consumption 24

Consumption 20

Consumption 19

c Consumption 10.5

Consumption

eng Consumption

ai Consumption

Consumption

Consumption

Consumption

ong Consumption

Consumption

Consumption

Consumption

Consumption

Consumption

Consumption

r Consumption

c Consumption 20

c Consumption 16

Consumption

Traditional Chinese medicine 20 RMB animal�1

rinoides and juvenile Plotosus lineatus.

Hainanese.

U. Krumme et al. / Continental Shelf Research 57 (2013) 105–116112

The single rod is also used to lock the net in the resting position(Fig. 5).

For assembly of the net, de-barked poles of 45 m height and�6 cm diameter are used, usually from conifer wood (Hainanesename: m �u ma wang, standard Mandarin name: song sh �u). It isnoteworthy that the poles are not buried but only stand on thesubstrate. A V-shaped ground rope prevents the base of the polefrom gliding forward when the net is lowered backwards(Fig. 4(A)). The end of the anchoring and V-shaped ground ropesare often split in two ends and are fixed by two ground stakes (seeFigs. 2 and 3; ropes 3r, 4r, 4l). Ground stakes are driven into thesubstrate using a bit-like connector plug whose tip fits tightly intoone end of the stake. This enables the construction in subtidalareas. A rope running through a transverse hole in the groundstake is used to tightly join the stake and connector plug. Thesledgehammer drives the connector plug into the substrate withthe ground stake at its tip. Once the ground stake is set, the ropeis removed. The mode of construction of lift nets suggests that it islikely an ancient artisanal fishery that has persisted over thecenturies.

Prior to typhoons, many fishers detach their lift nets and lowerthe poles to avoid damage. However, the towers are oftenbattered and require repair after typhoons. A net costs 2000–3000 RMB and has a lifetime of 2–6 years. In former times, themesh size was about 3 cm. Today, mesh sizes range from 1.5 to2.0 cm between knots.

4.7. Fishing times, capture methods, and target species

The mean number of fishing days per week was 3.7 (71 SD;range: 2–6 days). Lift net fisher in the clearer water of the back-reef area usually work at daytime (towers are usually roofed).Their major targets are mullets (Mugilidae), which are capturedusing sight. The use of the nets in the back-reef area is limitedduring low tides when the water level is o1 m.

Lift nets in the more turbid river and lagoon area are usuallyoperated at night using light to attract fishes and invertebrates(towers often lack roofs). Soak time at night is 1–3 h. In caseswhere fishing is done during the daytime (see below), soak timesrange from 20–30 min to 1 h. In former times, the lamps hangingabove the center of the nets were powered by gas or oil; since the

Fig. 6. Market chains of artisanal fishery landings at the jetty for ferry boats in Qing

Middleman local; Mmo: Middleman from outside; Mm: middleman (unspecified).

1980s self-made power lines often connect the lamps to thepower grid. The lift nets are not operated during phases ofstronger tidal currents. Fishers in the river/lagoon area capturea diverse set of nektonic species.

The net is emptied after each haul. If very few fishes arecaught, the net is lowered again and the fish can swim away. Thelift net fishery is virtually free of bycatch because even the partthat would actually be discarded is used as supplementary feedfor ponds or floating net cages. Scientific samples using lift netsrecorded 4120 nektonic species in the Wenchang/Wenjiaoestuary (Krumme and Wang, unpublished data). The majornektonic organisms caught with lift nets are listed in Table 2.The daily catch of a lift net is highly variable, ranging from no fish oro1–50 kg, and with a mean of 12 kg. One of our interviewees made arecord catch of 1.75 t of the clupeid Clupanodon thrissa with a singlehaul in the lagoon in July 2004 which was sold at Qinglan harbor asfish feed at 2 RMB kg�1. The catch composition of the lift nets differsamong estuarine zones and changes over time (e.g., with season andthe day/night cycle) (Ton That Phap, 2000; Krumme and Wang,unpublished data).

4.8. Marketing channels, sales and prices

The fishers store their catch in styrofoam boxes without ice.Zero to 10% of a catch is kept for own domestic consumption.The bulk (90–100%) is sold by the fisher himself or his wife, bothfor consumption and as aquaculture feed. The fishers in the riverand back-reef area sell their catch exclusively at local villagemarkets. Buyers are local people (mainly farmers) but also middle-men. The fishers from the lagoon area sell their catch largely atQinglan harbor, though minor catches may be sold at their village.

The ferry boat jetty at Qinglan harbor is the major landing site forthe artisanal fishery of the lagoon area. The sales take place beforesunrise (Supplement 1f). The catch is mainly sold to middlemen,owners of ponds and floating net cages. There are four majorcategories derived from the division of the catch into dead or liveand small or larger organisms. The lift net landings belong to thecategory dead, and fishes are mostly small and rarely large.

Larger dead fishes (fishes 410 cm or 40.25 kg) of the artisanalfishery can originate from the lift, trammel, or centipede nets,or other gear types (Supplement 1(a)–(e)). Once bought by a

lan (N 19.566520, E 110.820780), East Hainan, northern South China Sea. Mml:

Table 3Relative proportion of nektonic organisms in the total lift net catch (by weight)

used for consumption and low value/trash fish in three salinity zones of the

Wenchang estuary, East Hainan.

Sampling perioda Consumption: low value/trash fish

Upper estuary Middle estuary Outer estuary

1. 2007, August 57:43 37:63 17:83

2. 2007, September 47:53 65:35 67:33

3. 2008, July 57:43 27:73 73:27

4. 2008, August 49:51 9:91 50:50

5. 2009, March n.d. n.d. 68:32

6. 2009, April 57:43 15:85 71:29

Mean 53:47 29:71 66:34

a Each ratio is based on about 40 standardized spring tide samples taken

during 24 h; ‘‘n.d.’’: no data.

U. Krumme et al. / Continental Shelf Research 57 (2013) 105–116 113

middleman, the large dead fishes cannot be traced back to theirfishery because the middlemen buy the fishes irrespective of theoriginal gear type used. In general, larger dead fishes are used forconsumption in private households or in restaurants. Their pricesrange from �20 to 120 RMB kg�1 (Table 2). They are sold mostly atlocal markets, but are also transported to Wenchang and sometimeseven to Haikou. Middlemen are locals or come from outside (e.g.,Wenchang), and the market chain can consist of several transactionsbefore reaching the final consumer (Fig. 6).

By contrast, small dead fishes (fishes o10 cm length) sold at theferry boat jetty at Qinglan harbor mainly originate from the lift netfishery. Smaller fishes or fishes of poor quality are sold as feed tolocal shrimp and fish ponds, floating net cages, and, rarely, as feedfor pigs or chicken. Fishes used for feed include small juveniles ofGerreidae, Leiognathidae, Mugilidae, and Siganidae or species withsmall-sized adults such as Ambassidae, Clupeidae, Engraulidae orGobiidae (Table 2). Their use as feed corresponds with a low price of2–4 RMB kg�1. Mariculturists of the area add small dead fishes tothe commercial feed to increase the feeds’ quantity of protein.The small fishes are passed through a hand-operated masticatortogether with the commercial feed, water is added, and the modifiedfeed is fed to the animals. Small dead fishes have been used assupplementary feed in shrimp and fish ponds since the 1980s.Owners of floating net cages keep larger live fishes and reefinvertebrates. Products from both forms of mariculture enter theprofitable live food trade, which exclusively supplies restaurants.The marketing channels of the live food trade extend from theregional level (Wenchang, Haikou) to as far as Hongkong, wheredemand is highest (Sadovy and Vincent, 2002).

The engraulid Stolephorus indicus is the only small estuarinespecies originating from the lift net fishery that, when of good quality,can enter the commercial dry fish market and yield a higher price(13 RMB kg�1) (Table 2, Fig. 6). When S. indicus is abundant in thelagoon, the fish drier buys the fish at Qinglan harbor. The fish is eithercooked in brine prior to sun-drying or is freshly dried in the sun for 2days. Dried fish is put in plastic bags that are filled into cardboardboxes. The products of the five family-run drying operations aroundQinglan are jointly sent to a middleman in Guangzhou, who is arelative of one of the families. In Guangzhou the fish is stored, re-packed and distributed to supermarkets. However, the lift net fisheryonly holds a minor stake in the overall low value/trash fish economy.The main supply for fish drying usually originates from the commer-cial fishery operating outside the closed line and is mainly comprisedof Scombridae, marine Clupeidae or Sphyraena spp.

General data are missing, but prices for marine products areusually higher in winter when supply is reduced due to lowerwater temperatures and lower fish abundances. In summer, pricesincrease temporarily when the commercial fleet is incapacitatedfor work; namely during (1) the fishing moratorium from June toAugust and (2) typhoon periods when the commercial fleetshelters in the harbors. Some lift net fishers of the lagoon areareported that they try to work day and night in response to thetemporary price increase during the summer moratorium.

Given the fact that only a limited number of fishermen could beinterviewed due to time constraints, we also asked for similaritieswith neighboring lift net fishers from their area, e.g., in terms of age,fishing times, capture method, target species, and marketing chan-nels. The fishermen from the river, lagoon and back-reef areaconsistently answered that the other fishers in their area were alsoolder men, and operated their lift nets in essentially the same way,and used the same marketing channels they did.

4.9. Food:feed ratio and landing estimate

The mean overall food:feed ratio of the scientific lift netcatches was 48:52 (Table 3). The feed proportion was greatest

in the middle estuarine site (mean: 29:71), i.e., from the sub-sectors with the greatest number and sizes of lift nets, and lowestin the outer estuarine site (66:34).

A Qinglan middleman with about 20 years of experienceestimated that the daily landings of dead small fish from the liftnet fishery range between 0.1 and 0.5 t, of which 80% is used bythe floating net cages opposite of Qinglan harbor and 20% by thepond owners. Our approximation of the daily nektonic biomassremoval by the lift net fishery from the lagoon area proper in2009 is of a similar magnitude: �1.25 t daily total catch (197 liftnets from the subsectors b, d, e, f with a daily catch of 12 kg,operated during 3.7 days per week), i.e., 0.89 t (or 71%) of lowvalue/trash fish per day.

4.10. Historical changes in catch composition

All fishers reported decreasing catches, however with differentlevels of decline. The oldest fishers described a decline fromdecade to decade. Some fishers reported that over the years theyhad to increase the effort to catch the same amount of fish. Largerspecimens have become rarer. The income was stable over thelast years because rising prices for fish compensated for decreas-ing catches. The fishers did not report significant overall changesin fish species composition over the last 10 years. However, adecline of Gerres filamentosus (Gerreidae) and Upeneus tragula

(Mullidae) was witnessed by six and five fishers, respectively,(Table 4). Two of the five fishers from the lagoon area alsoreported a decline in Lutjanus russellii, Lethrinus lentjan andScatophagus argus. The interviewed fishers from the back-reefarea did not report any changes in species composition; they hadonly 4–8 years of fishing experience in this habitat.

4.11. Major problems and possible solutions

Surprisingly, most of the fishers seem never to have reflectedabout improving their situation. A few fishers from the lagoonand river area responded that there are too many nets and thattherefore less fish is left for each fisher. However, they hadopinions regarding improvements that might improve fishingconditions; including the treatment or diversion of effluents fromcities, shrimp ponds and industries, which are presently releaseddirectly into the river and lagoon, and restriction of the use ofcentipede nets, which they believe are responsible for the reduc-tion of larger fishes and are thus more responsible for overfishingin the area.

The answers reflected different levels of awareness among thefishers regarding environmental issues related to their fishery.The three coastal fishers only mentioned that their major problem

Table 4Fish species of the Wenchang/Wenjiao estuary (East Hainan) indicated by lift net

fishers in 2009 as much more abundant in the past, using color photos of 51

nektonic species from the area. n: total number of respondents per estuarine area.

Fish species (Family) Estuarine area

River (n¼2) Lagoon (n¼5) Coasta (n¼3)

Gerres filamentosus (Gerreidae) 1 5

Upeneus tragula (Mullidae) 5

Lutjanus russellii (Lutjanidae) 2

Lethrinus lentjan (Lethrinidae) 2

Scatophagus argus (Scatophagidae) 2

Diagramma picta (Haemulidae) 1

Fish species not photographed 1

Epinephelus bleekeri (Serrandiae) 1

Sardinella gibbosa (Clupeidae)b 1

a Fishers did not perceive changes, likely due to short fishing experience in the

back-reef area.b Nowadays Sardinella gibbosa is only used as feed because the population is

heavily infested (27% of all individuals caught in 2009) with endoparasitic

copepods belonging to Lernaeoceriformes, and less often with an isopode, likely

Nerocilla. In former times, the species was less infested and eaten by humans.

U. Krumme et al. / Continental Shelf Research 57 (2013) 105–116114

was the occurrence of typhoons. From the fishers of the lagoonand river area, five were aware of ongoing environmental pollutionand mentioned the effluents from the shrimp ponds as a severeproblem; specifically that the cleaning of shrimp ponds can causeintermittent and local fish mortality and temporarily reducecatches. Two respondents considered centipede nets, set beneaththeir lift nets, a major problem because they impede the operationof lift nets. They also complained about material that clogs theirnets, e.g., plastic waste and the water hyacinth Eichhornia sp. atpresent and mangrove litter in earlier times.

4.12. Scenario of decreased catches

Not one fisher would stop fishing even at a hypothetical 50%decline in catch. Many fishers answered with a counter question,e.g., ‘‘if I don’t fish, how can I survive?’’, or ‘‘we are old, what canwe do besides fishing?’’

4.13. Future of the lift net fishery

All of the fishers would like to see their children (most of themhave at least two children) have a different, better job. In fact,many of their children already have a job in the service sector.The future of the lift net fishery is viewed differently by differentfishers. Some suggested that the conditions for the lift net fisherywould not change. A few others worried that returning migrantworkers could enter the lift net fishery due to a lack of livelihoodalternatives; conflicts could arise from an increased number offishers competing for diminishing resources. One fisher from theriver area suggested that the number of lift nets would decreasebecause older men resigned from fishing and the lift net fisherywas not recruiting young men.

4.14. Ecosystem and fishery in retrospection

The interviews with the oldest fishers from the lagoon area(age: 56–74 years) revealed important information about thestate of the estuarine system in former times. They reportedconcordantly that in the past the lagoon had been deeper, cleaner,with greater export of plant matter from the mangroves, and thatthere had been much more fish. In line with the changes reportedby Li and Lee (1997), the oldest fishers reported that mangroveloss had taken place in three phases: (1) during the Great LeapForward (1958–1962) mangroves were used as firewood for steel

production; (2) during the subsequent famine mangroves wereconverted into rice fields; and (3) since the 1980s furthermangrove areas have been lost for the construction of maricultureponds, principally for shrimp production. The intensity andefficiency of the fishery increased after the death of Mao Zedongin 1976 when the fishery collectives vanished, motorized boatsbecame available and economic development started.

In former times, the demand for fish was much lower becausethere were fewer inhabitants but also fewer restaurants andtourists. Fishes from the lift net fishery were mostly used fordomestic consumption. Small fishes, which are nowadays sold asfeed, were used as food and eaten by the people in various waysof preparation. Today households and restaurants demand larger,higher-value fishes (of higher trophic level), which are continuallydecreasing in abundance. Given the scarcity of larger fishes in theartisanal shallow-water fisheries, the fishers appreciate theincreased demand for small dead fish by mariculture.

4.15. Lift net decline due to overfishing

The interviews and censuses suggest that the overall number ofnets increased in the 20th century, reached a maximum in therecent past and is currently in slight decline. Though unlikely, thisconclusion could be misleading if there were great seasonal fluctua-tions in lift net abundance, which were not quantified during ourstudy period. The major reason for the slight decline is likely due tothe decreasing economic viability of the fishery. Our standardizedlift net hauls revealed an overall mean nekton biomass of 0.3 g m�2

in the estuary (n¼643 lift net hauls; Krumme and Wang, unpub-lished data). This is strong evidence for severe overfishing becausethis value is 1–2 orders of magnitude lower than fish biomasses inother tropical estuaries; usually ranging between 1 and 15 g m�2

(Blaber, 1997; Krumme and Saint-Paul, 2010). In fact, during thepast decades the lift net fishers in Hainan responded to decliningcatches by three measures: (1) attraction of fishes through electriclight at night in the river and lagoon area; (2) decrease in mesh sizeto fish less selectively and consequently catch more fish; (3)increased fishing effort in days/year or hours/day and lift nets/fisher.However, besides lift nets, stow nets are also used as fixed gear andtogether with other widespread passive gears (trammel nets,centipede nets) contribute to growth overfishing in the estuary(Supplement 1b–e; Wang et al. 2009).

4.16. Mariculture demand supports the lift net fishery

A change from a food to a feed fishery apparently occurred inthe 1980s. The peoples’ food habits changed after the death ofMao Zedong. Fishes of lower trophic level were less valued forconsumption by the local population, which started to preferlarger fishes. Levin and Dufault (2010) termed a similar change insocietal value, i.e., a historical increase in average trophic level ofUS seafood cookbook recipes, ‘‘eating up the food web’’. Concur-rently, the rising demand of rural mariculture operators for lowvalue/trash fish provided the possibility to refine trash fish tomariculture feed and opened a new sales market for lesser-valuedfishes. These changes in the lift net fishery were further facilitatedby the proximity between appropriate fishing areas in the lagoon,the market place in Qinglan harbor, and the appearance ofmotorized boats. In the lagoon area the greatest abundance oflift nets (�60% of the 2009 total), greatest mean surface area ofnets, greatest concentration of lift net fishers in a single village(�50% of all lift net fisher) and greatest proportion of low value/trash fish (71% by weight) coincided (Fig. 1, subsectors b, d).

Presently, 450% of the lift net landings are low value/trash fish.Despite the low price (2–4 RMB kg�1), the sale of low value/trashfish contributes significantly to the income, and thus supports the

U. Krumme et al. / Continental Shelf Research 57 (2013) 105–116 115

economy of the lift net fishery. We hypothesize that the mariculturedemand supports an artisanal fishery at elevated fishing levelsdespite depleted resources. The mariculture demand tightens unsus-tainable levels of fishing and economically masks the criticaldepletion status of the estuarine fisheries resources.

Despite depleted nekton resources in the estuary, the lift netfishers displayed an imperturbable adherence to fishing (see4.12). This is in sharp contrast to the findings from Kenya(Cinner et al., 2008), where only the poorer households wouldcontinue fishing in the case of a severely declining fishery. InHainan, there were insignificant differences in wealth betweenthe fishers’ households. Most fishers were older than 50 years andconsidered the lift net fishing an early retirement activity. Allfishers would remain in the fishery even in scenarios of signifi-cantly declining catches because most of them lack occupationalalternatives and either have always been working with their liftnet or have actively opted for the lift net fishery.

However, because they have better job opportunities, very fewyoung men succeed the old lift net fishers. The lack of fishers with30 or 40 years of age suggests that these younger men have beenstaying away from the lift net fishery for more than a decade. It isnot clear if ‘‘new’’ retirees will continue to succeed the old fishersthat stop fishing. Fishing, due its open access nature, has pre-viously been thought as an activity of ‘‘the last resort for thepoorest’’ (Bene, 2003). Unlike this common trend in manycountries, statements from the fishers in East Hainan suggestthat young men from families with a fishing tradition havealready left the fishery to work as migrant workers due to thelack of prospects of success in fishing.

4.17. Implications for fisheries management

The lift net fishers provided valuable baseline information forassessing ecosystem changes (e.g., history of mangrove loss)(Johannes, 1984) since they have been fishing at the same sitefor many years and decades. The answers provided strongevidence that G. filamentosus and U. tragula had decreased inabundance, likely due to habitat loss, environmental degradationand overfishing. However, the responses also showed that majorenvironmental changes in the estuary must have taken placedecades ago, i.e., in the 1960s and 1980s, and the interviewees’statements regarding changes in the status of the fish communitylacked enough precision to be used as a reference in fisheriesmanagement. Even though most lift net fishers were at least 50years old, most of them had started fishing when major environ-mental changes had already taken place. Their information ratherdescribed the status of an estuarine fish community that had beendegraded for two to three decades — a phenomenon nowcommonly referred to as the ’’shifting baseline syndrome’’(Pauly, 1995). The extremely constrictive population pyramid oflift net fishers (i.e., lack of young fishers) will likely accelerate theprevalence of shifting baselines in the future (Turvey et al., 2010).

The high density of lift nets in the lagoon complicates naviga-tion and safety, especially at night, though local people seem toaccept the restricted navigation. On the other hand, the wide-spread presence of fixed fishing gear prevents the use of destruc-tive mobile fishing methods such as trawls that would lead tohabitat degradation. It also deserves mentioning that the lift netfishery unambiguously has a high cultural value that could bemobilized as a tourist attraction. Trained fishers could offerguided tours to their lift nets or other coastal sights, therebybecoming more independent from fishing (Chen, 2010).

Our research provides strong evidence that the moratoriumreduces the supply from offshore areas, and hence increases theprices for both fish used for consumption and low value/trashfish. This has adverse effects on inshore fisheries resources; it

causes a strong incentive for the artisanal inshore fisheries totemporarily increase fishing pressure because their activities arenot restricted by the summer moratorium. Since the summermonths are the major growth period of juvenile fishes in theirshallow inshore nursery grounds, the moratorium for the offshorefleet most likely exacerbates growth overfishing of the inshorestocks by the artisanal fisheries. This suggests that both thenational and provincial fishery acts require revision in order toensure the sustained, long-term use of coastal marine resources inChinese waters. For example, modelling approaches for thenorthern South China Sea suggest that ‘‘a combination of largemarine protected areas and effective effort reduction would benecessary to maintain fishery resources and biodiversity’’(Cheung and Pitcher, 2006; see also Cheung and Sumaila (2008)).

The low fish biomass suggests that it is a critical time forpolicy makers to address drivers of overfishing and mitigate thedepleted status of the inshore resources. This would requireaddressing several issues within the larger context of integratedcoastal zone management. Policy makers have to develop asuitable mix of management measures geared to the local con-text, e.g., an overall reduction of exploitation rates by artisanalfisheries, generation of alternative livelihood options (e.g., tour-ism), community-based management, temporal and/or spatialfishing closures, effective law enforcement, public awareness,reforestation of terrestrial and riparian vegetation in the catch-ment area, treatment of urban and aqua- and mariculture sewage,reforestation and restoration of mangrove area.

The government’s plan to turn Hainan into an ‘‘internationaltourist destination’’ and the construction of a space center inWenchang County will likely contribute to significant changes inenvironmental, economic and social settings of the coastal area.Therefore, the present study may also serve as an importantreference point for upcoming changes.

Acknowledgements

We thank the fishermen for their participation in the survey.S. Ruckert and S. Kleinertz helped with the identification ofSardinella gibbosa parasites. Marc Taylor proofread the article. D.Kaiser and U. Saint-Paul pointed to identical lift nets in Vietnam.This study was carried out within the frame of the bilateral Sino-German research project LANCET (Land-Sea Interactions alongCoastal Ecosystems of Tropical China: Hainan) funded jointly bythe German Federal Ministry of Education and Research (GrantNo. 03F0457A), the Chinese Ministry of Education (Contract No.IRT0427) and the Hainan Provincial Marine and Fishery Department.Two anonymous reviewers provided helpful comments thatimproved the quality of the manuscript.

Appendix A. Supplementary information

Supplementary data associated with this article can be found inthe online version at http://dx.doi.org/10.1016/j.csr.2012.04.011.

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