Trawl fishery of juvenile fishes and its impact on fish stock credit seminar jitendra

1

Major Advisor : Dr. S. Benakappa

Presented by:Jitendra Kumar

ID No. MFK 1109Department of Fisheries Resources and Management

Credit seminar presentation

Trawl Fishery of Juvenile Fishes and its Impact on

Fish Stock

2

Introduction

Terminology/ Definition

Results and Discussion

Impact Studies

Conclusion

OUTLINE

Methodology

References

Paper Presentation

3

• Trawling is a method of fishing that involves pulling a fishing net through the water behind one or more boats….

• The boats that are used for trawling are called trawlers or draggers

• The net that is used for trawling is called a trawl

• In Karnataka, bottom trawling was first introduced by the Japanese trawler M.S. Maru in 1961. (Kurup et al., 1987)

Trawling

4

• There are about 28 fish landing centres in the state. – Mangalore and Malpe in South Karnataka– Karwar in the north are main landing centres

• Mangalore and Malpe fisheries harbours account for more than 53% of the total marine fish landings and 43% of trawl fisheries of Karnataka.

• The main types of fishing are by – Purse-seine,– Trawling and – Gill netting

Cont..

5

• The use of the term “L V F” varies from country to country

• One category of LVF are those not used for direct human consumption, which may be either landed and discarded at the sea itself.

L V F

6

“Fish that have a low commercial value by virtue of their low quality, small size or low consumer preference –

or used for livestock/fish, either directly or through reduction to fish meal/oil”.

• The term “low-value fish” is preferred to “trash fish”.

• Trash fishes not only include non-commercial species, but also commercial species that are below minimum landing size (MLS) or less profitable species owing to market conditions.

TRASH FISH

FAO, 2012

APFIC, 2005

Catchpole et al.,2005

7

8

• An estimated 3.83 lakh t of bycatch valued at Rs. 192 crores was landed which form 27.8% of the total trawl catch.

At Mangalore: – An estimated 25,067 t of LVB valued at Rs. 25 crores was

landed by multiday trawlers (MDF) at Mangalore Fisheries Harbour.

CMFRI, 2011

Landing of LVB

The high demand for trash fish has been the major reason for increased landing.

9

T1 T2 T3 T4 T5 T6 T7 T8 T9 T100

2000

4000

6000

8000

10000

12000

Total (Kg)Trash fish

A case study at Mangalore landing center, Sep-Oct- 2012

T= Trawler No.

10

• The definition, “juveniles are young fish, mostly similar in form to

adult but not yet sexually mature” by Hubbs (1943).

A juvenile is an individual organism that has not yet reached its adult form, sexual maturity or size.

Juvenile

holds appropriate criteria for distinguishing juveniles of tropical fishes and it is used in the present study.

11

Catch of Juveniles (t) in trawlers along Karnataka in 2001 and 2002

SDFYear Total catch Juveniles catch %2001 31729 5205 16.52002 38880 5969 17.2

MDFYear Total catch Juveniles catch %2001 71207 15283 22.62002 70414 20947 25.1

Zacharia, et at., 2006

At Mangalore, highest percentage of juvenile fishes by weight in bycatch was of Nemipterus spp. (4,023 t) which results in an annual revenue loss of Rs.16.5 crores.

The economic loss due to discards of juvenile fishes by trawlers at Calicut is an estimated Rs.6.6 crores.

Estimations of Low value/Trash fish production in Asia-Pacific (tonnes)

Country Low value/trash

fish

% of total catch

Dominant gear Year of estimation

Bangladesh 71 000 17% Gill nets (48%)Non-mechanised set bags (42%)

2001-2002

China 5 316 000 38% Trawl 2001

India 271 000 10-20% Trawl 2003

Viet Nam 933 183 36% Trawl 2001

FAO 2005, 12

13

14

Category I

Adult

Juvenile

Category II

Adult in other gear

Juvenile in trawler

Category III

But there is no adult catch

Juvenile in trawler

Categories

Materials and Methods

15

Study Location

16

Results and discussion

108 species of finfishes

4 species of cephalopods

12 species of shrimps

At Mangalore and Malpe,

Category III: Epinephelus species especially E. diacanthusin which “protogyny” was reported

Category I: Thread fin breams, Soles, Ribbonfishes, Scianids, Carangids and Pomfrets

Category II: Seerfishes, Indian mackerel and oil sardines

Among the important species

17

Important groups of juveniles

• Groupers, • Thread fin breams,• Soles, • Ribbon fishes, • Scianids,• Carangids,• Pomfrets, • Seer fishes• Indian mackerel

Nemipterus mesoprion was more

18

19

20

21

Category I

N. mesoprionJuvenile :- 42% by No.

22% by wt. TC- 13,386 t JC- 2,914 tJuveniles %:-

Dec (96%)Nov (86%)

Jan to April:- 50% - 69%.

Finfishes:

N. japonicus Juvenile :- 35% by No.

12% by wt. TC- 5,780 t JC- 696 tJuveniles %:-

March (58%)Feb, Dec and Jan

53%, 47% and 42%, respectively

22

In sole, Cynoglossus macrostomus

Juvenile :- 35% by No. 26% by wt.

TC- 4,599 t JC- 1,119 tJuveniles %:-

Feb (63%). Jan, April and Sep

60%, 58%, and 49%, respectively

In whitefish, Lactarius lactarius,

Juvenile :- 35% by No. 18% by wt.

TC- 553 t JC- 97 tJuveniles %:-

June 64%, Aug and Sep,

61% and 56%, respectively.

23

Juvenile :- 5% by No. 1% by wt.

TC- 25,471 t JC- 341 t

Juveniles %:- Jan, Feb and March,

~12%.

Juvenile :- 15% by No. 5% by wt.

TC- 2,559 t JC- 118 t

Juveniles %:- Jan (48%)

Oct (38%) and Nov (19%).

In ribbonfish, Trichiurus lepturus In carangid, Decapterus russelli

24

Shellfishes:

In shrimp, Metapenaeus dobsoni

Juvenile :- 15% by No. 8% by wt. (64 t)

Juveniles %:- Dec (49%)Jan (10%) and March (9%).

In M. monoceros,

Juvenile :- 7% by No. 2% by wt. (61

t)Juveniles %:- May 22%.

Juvenile :- 6% by No. 2% by wt. (20 t)

Juveniles %:- Feb (16%)

In Solenocera choprai

25

In cuttle fish, Sepia pharaonis

Juvenile :- 13% by No. 2% by wt.

TC- 6,165 t JC- 123 t

Juveniles %:- March (33%) followed by Feb

(32%) and May (26%).

In squid, Loligo duvaucelli

Juvenile :- 20% by No. 3% by wt.

TC- 6,698 t JC- 201 t

Juveniles %:- April (58%) and another peak was observed in Oct (30%).

26

Category II

Seerfish, Scomberomorus commerson

Juvenile :- 16% by wt. TC- 183 t JC- 183 tJuveniles %:- all the months 100% of the

catch comprised of juveniles.

Catch was highest in March (26%) followed by Feb, Sep, Dec and Jan with

18%, 13%, 10% and 9%, respectively.

Muthiah & Pillai (2003) stated that out of 11.61 t million S. commerson landed by trawlers, only less than 1% get a chance to reproduce once before they were caught.

In Indian mackerel and oil sardine, influence of juvenile fishery in trawl was found to be negligible when compared with total landing from the coast.

27

Category III

In Epinephelus diacanthus

All the fishes caught were immature females

TC- 3,646 t JC- 3,573t98% wt 99% No.Big fishes were rarely caught, which were

not available for maturity studies

28

Impact Studies

Category I

• The juvenile fishery is damaging the adult catch in trawl itself.

Category II• The losses are occurring in gears other than

trawls, which are the major gear for those fishery.

Category III

• The impact is to be studied in wide geological platform where no data is available on the adult fishery from the area of fishing of juveniles

29

An example in the first category, N. mesoprion catch was analyzed and results are given in tables

Yield in 2006: 13,347 t value of ` 1,258 lakh

30

The resulting yield is 14,293 t with an increase in weight of 7% and an increase in value of 23% ( ` 286 lakh).

If the fishing mortality upto a size of MSM is reduced to zero

The increased percentage for value reflects the increased value realized for bigger sized fishes.

31

In the second category, where adults are caught by gears other than trawls, S. commerson

32

Yield from gillnet and trawl during 2006 was 1,287 t value of ` 1,390 lakh

If the trawl is not catching the juveniles of seerfishes(if fishing mortality zero),

the projected yield in gillnet is 1541 t weight of 20% value of 29% (406 lakh rupees).

33

• Its is often argued in tropical multispecies trawl fisheries, It is impossible to make policies for avoiding juvenile catches.

• However, by incorporating the knowledge about temporal and spatial

juvenile abundance data, it is possible to formulate policies to reduce juvenile fishery.

• From the landing data, it is possible for us to identify the peak months of juvenile exploitation.

• Trawlers - equipped with geographical positioning systems

• These policies can be implemented under responsible fisheries guidelines, so as to minimize the damages occurring to the commercial fishery due to juvenile exploitation.

34

Dan Watson devised a system based on a series of escape rings for fish – which can be fitted to a fisherman's trawler net

won a prestigious international award for creating a "humane" net to make fishing more sustainable by preventing small fish

Designed by: Dan Watson Thursday 8 Nov 2 01 2

Source: www.guardian.co.uk/environment/2012/nov/08/humane-fishing-net-dyson-award

35

Fishing net with emergency exits

The net is designed to make commercial fishing more sustainable by reducing the number of non-target and juvenile fish picked up by trawlers,

Watson explained to the BBC that about 20 rings are needed per net, costing a total of around $790 (£500). ` ~ 43000

36

APFIC. 2005. Regional workshop on Low value and “trash fish” in the Asia-Pacific region. Asia-Pacific Fishery Commission. pp 1-6

CMFRI. 2010-11. CMFRI annual report 2010-2011: pp 41-43.DINESHBABU, A. P. AND RADHAKRISHNAN, E.V., 2009. Trawl fishery of juvenile

fishes along Mangalore- Malpe coast of Karnataka and its impact on fish stock, Asian Fish. Sci. 22: 491-500.

DINESHBABU, A. P., THOMAS, S. AND RADHAKRISHNAN, E. V., 2012. Spatio-temporal analysis and impact assessment of trawl by catch of Karnataka to suggest operation based fishery management options, Indian J. Fish., 59(2): 27-38.

FAO. 2012. The state of world Fisheries and Aquaculture. FAO, Fisheries and Aquaculture Department. Rome, pp 194-196.

KURUP, K. N., NAIR, G. K. K., ANNAM, V. P., KANT, A., BEENA, M. R., AND KHAMBADKAR, L. 1987. An appraisal of the marine fisheries of Karnataka and Goa. CMFRI Sp. Publ., 36: 1-104.

ZACHARIA, P. U., KRISHNAKUMAR, P. K., DURGEKAR, R. N., KRISHNAN, A. A., AND MUTHIAH, C. 2006. Assessment of bycatch and discards associated with bottom trawling along Karnataka coast, India. School of Industrial Fisheries, Cochin University of Science & Technology, Cochin. pp: 434-445.

37