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New Zealand Journal of Marine and Freshwater Research

ISSN: 0028-8330 (Print) 1175-8805 (Online) Journal homepage: http://www.tandfonline.com/loi/tnzm20

Direct impacts of commercial and recreationalfishing on spiny lobster, Panulirus interruptus,populations at Santa Catalina Island, California,United States

Matthew Iacchei , Patrick Robinson & Kathy Ann Miller

To cite this article: Matthew Iacchei , Patrick Robinson & Kathy Ann Miller (2005) Directimpacts of commercial and recreational fishing on spiny lobster, Panulirus interruptus,populations at Santa Catalina Island, California, United States, New Zealand Journal of Marineand Freshwater Research, 39:6, 1201-1214, DOI: 10.1080/00288330.2005.9517386

To link to this article: http://dx.doi.org/10.1080/00288330.2005.9517386

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New Zealand Journal of Marine and Freshwater Research, 2005, Vol. 39Iaccheietal.—Catalinaspinylobsterfisheries: 1201-12140028-8330/05/3906-1201 © The Royal Society of New Zealand 2005

1201

Direct impacts of commercial and recreational fishingon spiny lobster, Panulirus interruptus, populationsat Santa Catalina Island, California, United States

MATTHEW IACCHEIPATRICK ROBINSONKATHY ANN MILLER*

Wrigley Marine Science CenterWrigley Institute for Environmental StudiesUniversity of Southern California1 Big Fisherman CoveAvalon, CA 90704 United States

*Present address: University Herbarium, Universityof California, Berkeley, CA 94720 United States,email: kathyannmiller@berkeley.edu

recreational and commercial areas was 92% and45%, respectively, of biomass in the INT reserve.Fecundity in the recreational and commercial areaswas 83% and 42%, respectively, of fecundity in theINT reserve. This study provides preliminary datafor future ecological studies and fisheries manage-ment evaluations.

Keywords Panulirus interruptus; spiny lobster;recreational fishery; commercial fishery; marineprotected area; marine reserve; trap survey; SantaCatalina Island

Abstract The California spiny or red rock lobster,Panulirus interruptus, is an ecologically and eco-nomically important species that has been exploitedsince the 1800s. No previous study in California hasassessed the impacts of the recreational or commer-cial lobster harvest. Before the 2003-04 commercialand recreational lobster seasons, we conducted afishery-independent trap survey at Santa CatalinaIsland to document the impact of the lobster fisher-ies on the size structure, abundance, and sex ratiosof mature P. interruptus (>65 mm carapace length(CL)). We concurrently sampled a predominantlycommercially fished area, a recreationally fishedarea, and a 23-year-old invertebrate no-take (INT)reserve. Relative to the INT reserve, legal-size lob-sters in the recreational area were similar in CL, but31% less abundant. Legal-size lobsters in the com-mercial area were 8% smaller and 70% less abun-dant than those in the INT reserve. The sex ratio oflegal-size lobsters, although near 50:50 in the rec-reational and INT reserve areas, was male-domi-nated (67:33) in the commercial area. Differences inCPUE and mean CL of sub-legal lobsters in the rec-reational and commercial areas suggest that factorsin addition to harvesting pressure may affect thesepopulations. Total biomass of mature lobsters in the

M04076; Online publication date 9 November 2005Received 31 March 2004; accepted 15 April 2005

INTRODUCTION

For over a century, the California spiny or red rocklobster, Panulirus interruptus (Randall), has beenfished commercially and recreationally throughoutits range from Point Conception, California, UnitedStates to Magdalena Bay, Baja California, Mexico(Duffy 1973). In 1888, commercial fishers caught104 800 kg of lobster in California using 260 traps,whereas in 1973,19 000 traps were required to catchapproximately the same amount (105 800 kg)(Odemar et al. 1975). Commercial landings havecontinued to increase, with an average of 294 800 kglanded over the past 5 years (California Departmentof Fish and Game (CDFG) unpubl. data). Little isknown about the intensity or effects of the Californiarecreational lobster fishery or the current status oflobster populations (Barsky 2001). Bahia Tortugas,in central Baja California, Mexico is the mostproductive P. interruptus fishery (Vega 2003) andMexico is most likely an important larval source forthe southern California populations (Pringle 1986).Recent investigations have focused on the ecologyand fishery dynamics of P. interruptus in Mexico(see references in Vega 2003), but little research hasbeen conducted on this subtropical species inCalifornia, at the northern end of its range, wheredifferent environmental conditions, fishing regu-lations, and harvesting pressures influence popu-lation structure.

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1202 New Zealand Journal of Marine and Freshwater Research, 2005, Vol. 39

33.41-118.63 -118.58 -118.53 -118.48

Fig. 1 Location of study sites at Santa Catalina Island, CA, United States. The study area encompasses commercial,recreational, and invertebrate no-take (INT) reserve areas. The commercial area is adjacent to additional commer-cially fished waters. The INT reserve is flanked by recreational fishing areas.

In California, juvenile lobsters occupy shallow(0–4 m) Phyllospadix spp. (surfgrass) habitats fortheir first 2 years, and have different behaviour andprey than mature lobsters, which live gregariouslyin dens situated in kelp forests (Engle 1979).Lobsters become reproductively mature at carapacelengths between 63 and 72 mm (4-5 years of age)(Engle 1979; Barsky 2001; Vega 2003), a size rangethat corresponds with the lower size limit oftrappable lobsters (Iacchei et al. pers. obs.). Maturelobsters play an important ecological role in southernCalifornia, directly controlling the size distributionsand abundance of intertidal (Robles 1987) andsubtidal (Tegner & Levin 1983) prey species.Lobsters may also have community-wide influences,indirectly affecting habitat-forming species such asMacrocystis pyrifera (Pinnegar et al. 2000). Areduction in the abundance and size of spiny lobstersfrom historical levels has changed their functionalrole in the kelp forest community (Dayton et al.1998). We conducted a short-term study of theimpact of commercial and recreational fishingpressure on P. interruptus at Santa Catalina Island,California, United States (Fig. 1). Using a fishery-independent trap survey, we simultaneously sampleda commercially and recreationally fished area, arecreationally fished area, and the invertebrate

no-take (INT) reserve before the opening of the2003-04 lobster season. We estimated relative abun-dances (CPUE, catch per unit effort), size structures(CL, carapace length), and sex ratios of sub-legal(61-82.5 mm CL) and legal-size (>82.5 mm)lobsters in each area to document the impact of thesefisheries and to provide a snapshot of the status ofpopulations of mature lobster at Santa CatalinaIsland. Our study provides preliminary data forlarger scale monitoring programmes in southernCalifornia.

METHODS

Study sitesSanta Catalina Island (33.4°N, 118.5°W), one of theeight California Channel Islands, is located 20nautical miles off the coast of Los Angeles,California (Fig. 1). We focused our studies on the21 km of coastline comprising the west end of theisland from Lion's Head (33.455°N, 118.503°W) onthe leeward side to Catalina Harbor (33.422°N,118.513°W) on the windward side. The west end ofthe island has predominately steep rocky shores withnarrow kelp beds. On the windward side, the islandsupports a small, geographically discrete,

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Iacchei et al.—Catalina spiny lobster fisheries 1203

commercial trap fishery. Both sides of the island arerecreationally fished. In 1980, an INT reserve, closedto both recreational and commercial lobster fishing,was established on the leeward side (Fig. 1).

Commercial fishing occurs on the windward sideof the island, where 3-5 fishers catch lobsters with750-1000 traps. According to the CaliforniaDepartment of Fish and Game catch records (CDFGunpubl. data), commercial lobster fishers trapped246 827 (83 079 legals) lobsters at Catalina Islandfrom the 1998-99 season until the 2002-03 season,with an average of 16 616 legal-size lobsters perseason. Approximately 40% of these lobsters werecaught in our study area on the west end of the island.Recreational fishers are allowed to catch lobsters onboth sides of the island by hand or with hoop netsand are limited to a daily bag limit of seven lobstersper person. From the 1998-99 season until the 2002-03 season, 8660 recreational lobster fishers caught6317 lobsters from charter dive boats at CatalinaIsland, with an average of 1261 lobsters caught by1732 fishers per year (CDFG unpubl. data). Ourrecreational study area is within the region where57% of this effort has taken place. We examinedCDFG recreational lobster boat logs for the past ninefishing seasons (CDFG unpubl. data) and conducteda phone survey of charter dive boats (Iacchei et al.unpubl. data) to calculate that c. 10% of recreationallobster fishing takes place on the windward side ofthe island. According to dive boat operators,recreational lobster fishers prefer the leeward sideof the island because it is more accessible and it isclosed to commercial fishing. Recreational take fromprivate boaters and shore-divers is unknown, butanecdotal evidence suggests a similar geographicpattern. The annual recreational lobster take on thewindward side of the island is 0.26% of thecommercial take; therefore, we refer to the windwardside as the "commercial area" in our analyses.Recreational harvest begins the weekend before theopening of the commercial season (the firstWednesday in October). Both seasons end on the firstWednesday after 15 March. These seasons aredesigned to protect reproducing and moulting lobsters.

The INT reserve, extending 4.14 km from Lion'sHead to Arrow Point on the leeward side of theisland, was established in 1980 by the CDFG toprotect invertebrate game species including lobster,abalone (Haliotis corrugata and H. fulgens), andscallop (Crassedoma giganteum). Line fishing ispermitted. The proximity of the Isthmus HarborPatrol and the vigilance of the local communityminimise poaching opportunities.

SamplingWe sampled lobster populations in the INT reserve,a recreationally fished area, and a commerciallyfished area each day from 17 September through 30September 2003, just before the opening of the2003-04 lobster season. Effort was proportional tolength of coastline for each area; approximatelytwice as many traps (104) were set in the commercialarea than in either the recreational area (51) or theINT reserve (54). This difference in effort was alsonecessary to catch a comparable number of lobstersin all three areas. We used 24 commercial-stylelobster traps (92 cm ¥ 72 cm ¥ 42 cm) constructedof 10.0 cm ¥ 4.5 cm plastic-coated wire mesh (C&MWire Products, United States) with a funnel hoopdiameter of 19.0 cm. Our research traps were notequipped with the escape port required by law incommercial traps, enabling us to consistently capturelobsters as small as 61 mm CL. We baited traps dailywith 450 g frozen mackerel (Scomber japonicus)placed in perforated plastic containers. Metaldestruction clips secured the trap lids and preventedtampering by divers. We dropped traps in a stratifiedrandom pattern with a 30 m minimum distancebetween each trap to minimise trap competition(Smith & Tremblay 2002). The traps were set inrocky, kelp forest habitat in depths ranging from 3to 15 m. We recorded the GPS coordinates for eachdrop location. Traps fished overnight (c. 12 h) andwere hand-pulled the following day. Lobsters wereexposed to air for no longer than 15 min and werereturned to their trap location.

We obtained hourly temperature data from 1997to 2004 from the Catalina Conservancy Divers(CCD) (www.ccd.org) and calculated mean dailytemperatures. CCD deploy StowAway TidbiT®temperature loggers (Onset Computer Corporation,Bourne, MA, United States) at 18 m at Cactus Bay(windward) and the Wrigley Marine Science Center(leeward).

To describe the structure of the populations, werecorded the sex and measured the CL of each lobster(Mitutoyo model CD-6"GS Digital calipers,0.25 mm accuracy). We marked uropods of eachlobster with a region-specific hole punch to preventre-sampling and to monitor movement betweenareas. We weighed 906 lobsters (Acculab VI6000portable electronic balance) to obtain a length-to-mass relationship for determining the biomass ofmature lobsters in each area. To maximise precision,the same individual measured CL and weighed eachlobster. We applied the CL to mass equation to oursize-frequency distributions, and summed the masses

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New Zealand Journal of Marine and Freshwater Research, 2005, Vol. 39

17-

CD

15 -CD

E 14 H,<D

13 -

-Windward

• Leeward

1216 Sep

i

Fig. 2 Temperature (°C) at 18 mwater depth on the windward andleeward sides of Santa Catalina Is-land, CA, United States: A, duringthe 2-week lobster (Panulirusinterruptus) sampling period; B,the 6 years before the study. Onesubset of data from each side of theisland is missing from the figurebecause of lost temperature log-gers.

21 SepDate

26 Sep 1 Oct

22

20 -

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(Te

mpe

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18 -

14 -

12 -

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1997 1998 1999 2000 2001 2002 2003 2004 2005Year

for each area to obtain a relative total biomassestimate for each area. Biomass estimates wereadjusted to be proportional to trapping effort in eacharea. Using data from Lindberg (1955), we estimatedfecundity for female lobsters in each area. Totallength (TL) used by Lindberg was converted to thestandard CL using the equation:

y = 3.8053x-1.9284

where y is CL (mm) and x is TL (cm) (R2 = 0.98).This relationship was obtained using the I-extractor3.0 digital extracting program to extrapolate values

from the TL to CL graph (Lindberg 1955). A tablerelating TL to fecundity in Lindberg (1955) was usedto create an equation to describe the CL to fecundityrelationship (see Results). We applied this equationto the size-frequency distributions, and summed thefecundities for each area to obtain a relative totalfecundity estimate for each area. Total fecundityestimates were adjusted to be proportional totrapping effort in each area. Though this was our bestsource of data, multiple conversions were needed toobtain these relationships, which can compounderror; therefore, we provided confidence intervals forthe final results.

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Iacchei et al.—Catalina spiny lobster fisheries 1205

Data analysisWe used one-way ANOVA tests with Tukey post-hoc analyses to compare differences in mean CL andCPUE (defined as mean number of lobsters per trap)in the three areas. Because mean CL and CPUE datawere non-normally distributed and the varianceswere not homogeneous (Levene's test, Levene1960), we natural log-transformed the data. We useda chi-square goodness-of-fit test to test for deviationsfrom a 50/50 sex ratio in each of the areas, and acontingency table (chi-square) to compare the sexratios among the areas. The Kolmogorov-Smirnovtest (Chakravarti et al. 1967) was used to comparesize-frequency distributions. Significance level was0.05 for all tests. We used SYSTAT 9 and JMP 5.1software programs.

RESULTS

Temperature data from the windward and leewardsides of the island were similar at both the 6 year and2 week temporal scales (Fig. 2). For the 6 yearsbefore this study, temperatures on both sides of theisland followed similar seasonal trends, but thewindward side consistently experienced a slightlylower temperature in the winter months. During ourtrapping period in 2003, differences of up to 2°C inmean daily temperature were observed on a givenday, but data from both sides of the island followedthe same cooling trend.

We trapped 376 lobsters (104 traps) in thecommercial fishing area, 315 lobsters (51 traps) inthe recreational fishing area, and 345 lobsters (54traps) in the INT reserve. Based on region-specifictags, lobsters did not move between areas during ourstudy. CL in the commercial area ranged from61 mm to 110 mm, peaked at 75 mm, with a mean(±SD) of 77.86 ± 7.39 and a median of 77.64 mm(Fig. 3A). In the recreational area, CL ranged from62 mm to 146 mm, peaked at 74 mm, with a mean(±SD) of 81.02 ± 14.56 and a median of 77.62 mm(Fig. 3B). CL ranged from 60 mm to 127 mm in theINT reserve, with a peak at 76 mm, a mean (±SD)of 83.63 ± 13.45, and a median of 81.07 mm (Fig.3C). The INT reserve was the sole area where meansize was greater than the legal size limit (82.55 mmCL). The three CL size-frequency distributions weresignificantly different from one another (P < 0.001).Cumulative distribution graphs show that the sizedistributions of the sub-legal size classes were simi-lar in all three areas (Fig. 4B). A clear divergencefrom the INT reserve distribution occurred slightly

before the legal size limit in both the recreational areaand the commercial area (Fig. 4A). The recreationaland INT reserve size distributions were similar againfrom 105 mm to 115 mm CL, but in size classeslarger than 115 mm CL, there was a greaterabundance of lobsters in the recreational area thanin the INT reserve (Fig. 4A).

Mean CL of lobsters from each of the three areaswas inversely related to fishing pressure (Fig. 5,Table 1). Mean CL of lobsters in the INT reserve was3.1% greater than that in the recreational area, and6.9% greater than that in the commercial area.Within the sub-legal size classes, mean CL in thecommercial area was significantly greater than meanCL in the recreational area, but not significantlydifferent from the INT reserve (Fig. 5, Table 1).Mean CL of legal-size lobsters in the commercialarea was 8.4% less than that in the INT reserve and9.4% less than that in the recreational area. The INTreserve and recreational areas had comparable meanCL in both the sub-legal and legal size classes (Table1). The percentage of lobsters with CL greater thanthe legal size limit was inversely related to fishingpressure (Fig. 6).

There was no significant difference between mean(±SE) CPUE in the recreational (6.18 ± 0.58) andINT reserve (6.39 ± 0.54) areas, but mean CPUE ineach of these areas was significantly greater than inthe commercial area (3.62 ± 0.31) (Fig. 7, Table 2).Within the sub-legal size classes, mean CPUE in theINT reserve (3.37 ± 0.36) was not significantlydifferent from either fished area, but mean CPUE inthe recreational area (4.10 ± 0.48) was significantlygreater than mean CPUE in the commercial area(2.69 ± 0.26) (Table 2). In the legal size classes,CPUE was inversely related to fishing pressure (Fig.7). Mean CPUE (±SE) in the INT reserve (3.02 ±0.28) was significantly greater than mean CPUE inthe recreational area (2.08 ± 0.28), which was signifi-cantly greater than mean CPUE in the commercialarea (0.92 ± 0.10) (Table 2).

The sex ratio was female-biased in all three areas(Fig. 8, Table 3). In the sub-legal size classes,females were consistently twice as abundant asmales. In the legal size classes, there was an evensex ratio in both the INT reserve and recreationalareas, but males dominated in the commercial area(67%).

The CL-mass relationship was y = 0.0024(x)2.7945,where y is mass (g) and x is CL (mm) (R2 = 0.98).This relationship was similar for both males andfemales on both sides of the island (Iacchei et al.unpubl. data). The relative biomass of lobsters in the

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1206 New Zealand Journal of Marine and Freshwater Research, 2005, Vol. 39

Fig. 3 Carapace length (mm) fre-quency distributions of lobsters(Panulirus interruptus) trapped in:A, commercial area; B, recrea-tional area; and C, invertebrate no-take (INT) reserve. Arrowsindicate the legal size limit(82.55 mm CL).

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Carapace length (mm)

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Iacchei et al.—Catalina spiny lobster fisheries 1207

100

- - -CommercialRecreationalINT Reserve

70 80 90 100 110 120 130 140Carapace length (mm)

100

o

60 62 64 66 68 70 72 74 76 78 80 82Carapace length (mm)

Fig. 4 Cumulative distribution graphs for: A, total sizerange of trapped lobsters (Panulirus interruptus); and B,sub-legal lobsters only. Cumulative percentage of the to-tal number of lobsters trapped at each mm carapace length(CL) in the commercial area, the recreational area, andthe invertebrate no-take (INT) reserve. The black line inA represents the legal size limit (82.55 mm CL).

Sub-legal Post-legal

Fig. 5 Mean carapace length (CL) (±SE) of lobsters(Panulirus interruptus) trapped in the commercial area,recreational area, and invertebrate no-take (INT) reserve.All trappable size classes are represented at the left; theother categories are partitioned relative to the legal sizelimit (82.55 mm CL).

50 -i

45 •

Commercial Recreational INT Reserve

Fig. 6 Percentage of lobsters (Panulirus interruptus)larger than the legal size limit (82.55 mm carapace length)in the commercial area, recreational area, and invertebrateno-take (INT) reserve.

Table 1 Effect of fishing pressure on mean carapace length (CL) of Panulirus interruptus: One-way ANOVA withTukey post-hoc analyses. Sum of squares, degrees of freedom, mean square, F value and P value for all lobsters, sub-legal (< 82.5 mm CL) and legal (> 82.5 mm CL) size classes. Value in parentheses is mean CL (mm). (INT reserve,invertebrate no-take reserve.)

SS d.f. MS FPvalue

All lobstersCommercialRecreationalCommercialSub-legalCommercialRecreationalCommercialLegalCommercialRecreationalCommercial

(77.86) versus INT reserve (83.63)(81.02) versus INT reserve (83.63)(77.86) versus Recreational (81.02)

(74.67) versus INT reserve (73.65)(73.54) versus INT reserve (73.65)(74.67) versus Recreational (73.54)

(87.15) versus INT reserve (95.16)(96.22) versus INT reserve (95.16)(87.15) versus Recreational (96.22)

6974.13

213.58

5546.28

3487.07

106.79

2773.14

23.48

4.43

20.77

0.000.000.010.000.010.060.950.020.000.000.950.00

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1208 New Zealand Journal of Marine and Freshwater Research, 2005, Vol. 39

| •Commercial E3Recreational DINT Reserve |

Sub-legal Post-legal All Sub-legal Post-legal

Fig. 7 Mean number (±SE) of lobsters (Panulirus in-terruptus) caught per trap (CPUE, catch per unit effort)in the commercial area, recreational area, and invertebrateno-take (INT) reserve. All trappable size classes are rep-resented at the left; the other categories are partitionedrelative to the legal size limit (82.55 mm carapace length).

Fig. 8 Sex ratio (% female) of lobsters (Panulirus in-terruptus) trapped in the commercial area, recreationalarea, and invertebrate no-take (INT) reserve. All trappablesize classes are represented on the left; the other catego-ries are partitioned relative to the legal size limit(82.55 mm carapace length).

Table 2 Effect of fishing pressure on mean catch per unit effort (CPUE): One-way ANOVA with Tukey post-hocanalyses. Sum of squares, degrees of freedom, mean square, F value and P value for all lobsters, sub-legal (< 82.5 mmCL) and legal (> 82.5 mm CL) size classes. Value in parentheses is mean CPUE. (INT reserve, invertebrate no-takereserve.)

SS d.f. MS FPvalue

All lobstersCommercialRecreationalCommercialSub-legalCommercialRecreationalCommercialLegalCommercialRecreationalCommercial

(3.62) versus INT reserve (6.39)(6.18) versus INT reserve (6.39)(3.62) versus Recreational (6.18)

(2.69) versus INT reserve (3.37)(4.10) versus INT reserve (3.37)(2.69) versus Recreational (4.10)

(0.92) versus INT reserve (3.02)(2.08) versus INT reserve (3.02)(0.92) versus Recreational (2.08)

373.75

69.48

163.51

186.88

34.74

81.75

14.12

4.25

31.19

0.000.000.950.000.020.330.390.010.000.000.010.00

commercial area and recreational area was 45% and92%, respectively, of the relative biomass in the INTreserve (Table 4). The CL-fecundity relationship wasy = 0.0166 ¥ 3 5 3 7 where y is the number of eggs andx is the CL (mm) (R2 = 0.92). Calculated eggproduction (fecundity) in the commercial area andrecreational area was 42% and 83%, respectively, ofcalculated egg production in the INT reserve (Table5).

DISCUSSION

The separation of recreational and commerciallobster fisheries and the presence of a 23-year-oldINT reserve at Santa Catalina Island enabled us tomake the first fishery-independent estimates of thedirect effects of these fisheries on P. interruptus. Ourstudy suggests that recreational fishing has thepotential to decrease the abundance of legal-size

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Iacchei et al.—Catalina spiny lobster fisheries 1209

lobsters and the overall fecundity of mature lobsterpopulations, whereas commercial fishing has thepotential to cause population-level changes in P.interruptus by decreasing mean size, abundance,biomass, and fecundity of lobster populations.However, this study has several limitations. Thestudy was a natural experiment rather than anexperimental manipulation; thus, we cannot identifythe fisheries as the sole cause of the differencesobserved in the three populations. We collected dataover a short time period and did not address inter-annual variability, which may be significant (e.g.,Blonder et al. 1992). The relatively small scale ofthe study may limit its relevance to other regions

where fishing pressures and habitats differ. Despitethese limitations, the observed patterns weresignificant and warrant consideration.

Our study design relied on the hypothesis that thelobster population in the INT reserve served as acontrol or baseline for comparisons with fishedareas. Previous international studies have demon-strated the effectiveness of marine reserves inrebuilding lobster populations (reviewed by Gell &Roberts 2003). Important factors in determiningreserve effectiveness include the age of a reserve andthe movement pattern of the lobsters within it. Ourstudy took place 23 years after the closure of the INTreserve to recreational lobster fishers, far exceeding

Table 3 Effect of fishing pressure on sex ratio: chi-square contingency tables.Percentage female lobsters (Panulirus interruptus), degrees of freedom, chi-square value and P value for all lobsters, sub-legal (< 82.5 mm CL) and legal(> 82.5 mm CL) size classes. (INT reserve, invertebrate no-take reserve.)

Sex ratio (% female) d.f. r Pvalue

All lobstersCommercialRecreationalINT reserveSub-legalCommercialRecreationalINT reserveLegalCommercialRecreationalINT reserve

586259

676966

334851

1.19

0.60

6.25

0.55

0.74

0.04

Table 4 Comparison of relative biomass estimates. "% of INT reserve" category is the proportion of the area'srelative Panulirus interruptus biomass to the invertebrate no-take (INT) reserve's relative P. interruptus biomasstimes 100. "Relative biomass" is the total biomass of P. interruptus trapped in an area divided by the number of trapsused in that area. "95% CI" is the 95% confidence interval around the mean biomass of an area; the mean biomass isalso given. "n" is the number of P. interruptus trapped in each category.

All lobstersCommercialRecreationalINT reserveSub-legalCommercialRecreationalINT reserveLegalCommercialRecreationalINT reserve

% of INT reserve

45.0891.99

82.63122.59

24.2875.04

-

Relative biomass (g)

167134113708

109216201322

57917912386

Mean (g)

474563603

416399401

641895837

95% CI

(460-487)(522-604)(571-635)

(407–425)(389–409)(390-412)

(614-668)(802-989)(792-881)

n

367309332

273207178

94102154

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1210 New Zealand Journal of Marine and Freshwater Research, 2005, Vol. 39

the time necessary for other spiny lobster species toshow significant signs of recovery (Davis 1977;Kelly et al. 2000). The home range of P. interruptusis thought to be relatively small (Lindberg 1955). Wedid not observe any lobster movement between thethree areas during this study, but this could be anartefact of the short sampling period. In anotherstudy conducted at Santa CatalinaIsland, 85% of 305recaptured lobsters moved less than 360 m during anaverage of 3 months at large (Robinson et al. unpubl.data). This movement is relatively small comparedto the size of the INT reserve. Because we cannotcompare the current populations with pre-exploitation populations, the INT reserve is our bestapproximation of a baseline from which to evaluaterecreationally and commercially fished areas atSanta Catalina Island.

Studies of fishery-related impacts can be confoun-ded by spatio-temporal variability in factors that mayaffect lobster catchability, such as changes in watertemperature, storms, moon phase, and season(Frusher & Hoenig 2001; Ziegler et al. 2002, 2003;Vega 2003). We simultaneously sampled threegeographically adjacent areas subject to varyingfishing pressure around the west end of SantaCatalina Island to control for differences such asmoon phase, seasonal effects, and storms. Wesampled at the end of the summer, when wind andwave conditions are most similar on both sides ofthe island. Temperature has been hypothesised toinfluence timing of egg development, moulting, andan annual deep-water migration, all of which couldinfluence CPUE (Barsky 2001; Vega 2003). Despite

differences of up to 2°C, temperature trends on asmall temporal scale were similar between thewindward and leeward sides of the island (Fig. 2A).Temperature differences between the sides of theisland were not likely to cause a difference incatchability. Seasonal temperature trends during the6 years before the study were also similar; therefore,temperature is not likely to cause differences incumulative factors, such as growth, between the twosides of the island (Fig. 2B).

Two important differences for which simul-taneous sampling could not control are differencesin habitat and in larval supply. We controlled forhabitat differences as much as possible by trappingonly in rocky, kelp forest habitats in all three areas;however, this would not fully control for foodavailability or for predator density. Food availabilityhas been shown to influence growth rates in P.interruptus, but the generalist feeding strategy oflobsters minimises the chance that a change in oneprey's abundance would affect overall nutrition(Barsky 2001). Large discrepancies in theabundances of a variety of species are unlikely giventhat we trapped in similar habitats. Predation pres-sure should be similar in all three areas, especiallysince the INT reserve permits line fishing. Ifpredation pressure differs, abundances and sizedistributions of sub-legal P. interruptus may beaffected, but legal-size lobsters most likely reach asize refuge from predation (Engle 1979). Toinvestigate the possible influence of both theseenvironmental differences and potential geographicvariation in larval supply, we compared the sub-legal

Table 5 Comparison of relative fecundity estimates. "% of INT reserve" category is the proportion of the area'srelative Panulirus interruptus fecundity to the invertebrate no-take (INT) reserve's relative P. interruptus fecunditytimes 100. "Relative fecundity" is the total fecundity of P. interruptus trapped in an area divided by the number oftraps used in that area. "95% CI" is the 95% confidence interval around the mean fecundity of an area; the meanfecundity is also given. "n" is the number of P. interruptus females trapped in each category.

All lobstersCommercialRecreationalINT reserveSub-legalCommercialRecreationalINT reserveLegalCommercialRecreationalINT reserve

% of INT reserve

42.2083.35

84.10125.40

14.6855.73

-

Relative biomass (g)

156 067308 228369 783

123 317183 868146 629

32 749124 360223 154

Mean (g)

75 84581873101 362

70 08265 57567 101

109 869129 436152 536

95% CI

(73 073-78 618)(76 924-86 822)(93 822-108 902)

(67 789-72375)(62 906-68 245)(64 123-70 080)

(106 063-113 675)(120 643-138 228)(141 545-163 527)

n

214192197

183143118

314979

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Iacchei et al.—Catalina spiny lobster fisheries 1211

size classes that are not subject to fishing. If larvalsupplies were equal, and post-settlement conditionswere equivalent, we would predict that the portionof the population not subject to harvest ("sub-legals"<82.55 mm CL) in each area would be similar. Therewere no differences in the sex ratios of sub-legals inthe three different areas (Table 1); however, CPUEof sub-legal lobsters in the commercial area wassignificantly less than that in the recreational area,but not significantly different from that in the INTreserve. Mean CL in the commercial area wassignificantly greater than in the recreational area, butnot significantly different than the INT reserve(Tables 2 and 3). The differences in mean CL andCPUE between the recreational and commercialareas were small compared to the differences in the"all" (all size classes) and "legal" (>82.55 mm CL)data (Tables 2 and 3), but they suggest that otherfactors may be influencing these populations inaddition to fishing pressure.

Size-frequency distributions have been used toestimate recruitment changes through time (Ebert &Russell 1988). Our size-frequency distributionsshow slightly lower percentages of lobsters in the60-68 mm CL size classes in the commercial area(Fig. 3). This could indicate a few years of decreasedrecruitment in the commercial area relative to theother two areas, which would explain both the CPUEand mean CL patterns in the sub-legal lobsters.Alternatively, these differences could be a by-product of the fishery. DiNardo et al. (2002) showedthat sub-legal lobsters caught in the NorthwesternHawaiian Island trap fishery were subject to highmortality rates from handling and post-releasepredation. If growth is density dependent, then lowernumbers of sub-legal lobsters in the commercialarea, as well as the significant decrease in the numberof legal lobsters because of harvest, could promotefaster growth rates (and a higher mean CL). Furtherstudies are needed to determine if differences in thesub-legal size classes are from recruitment dynamics,fishery effects, or a combination of both.

We observed much greater differences in meanCL in the all and legal categories in the three areasthan in the sub-legal category, suggesting fisherieseffects. For all lobsters, mean CL in the recreationalarea was 2.6 mm less than in the INT reserve, butmean sizes of legal-size lobsters were not signifi-cantly different between these two areas. The size-frequency graphs show a greater abundance oflobsters in the larger size classes in the INT reserve,but the recreational area had a number of largelobsters, including the largest lobsters caught in our

study (Fig. 3). The effect of fishing on mean CL oflobsters was conspicuous in the commercial areawhere we trapped only three lobsters >100 mm CL.Mean CL of all lobsters was 5.7 mm less in thecommercial area than in the INT reserve and forlegal-size lobsters, mean CL in the commercial areawas 8 mm less than that in the INT reserve. For legalP. interruptus, 8 mm represents 4-8 years of growth(Odemar et al. 1975; Robinson et al. unpubl. data).

Although average harvesting pressure byrecreational lobster fishers is only 6% of that bycommercial fishers (CDFG unpubl. data), therelative abundance of legal-size lobsters in therecreational area was 31% lower than in the INTreserve. Recreational lobster fishing for P. argus inFlorida has caused much higher reductions in CPUE,ranging from 55% (Blonder et al. 1988) to 80%(Eggleston & Dahlgreen 2001). We did not observea reduction of this magnitude at Santa CatalinaIsland, possibly because the island is less accessible,the water is colder, and night diving in kelp ischallenging. In the commercial area, the relativeabundance of legal-size lobsters was 70% less thanthat in INT reserve. This is twice the reductionobserved in the recreational area, and falls in the mid-range of impacts by commercial fishing in otherspiny lobster species, where reductions from trapfisheries range from 38% to 99% (Davis 1977; Goñi2001). Both the size frequency and the cumulativedistribution plots show that the number of lobstersin the commercial area decreased sharply above thelegal size limit (Fig. 3,4). This pattern is in markedcontrast to other spiny lobster fisheries where the sizedistributions may be shifted, but lack a distinct dropin abundance near the legal size limit (Davis 1977;Kelly et al. 2000). The small number of large lobstersin the commercial area supports the hypothesis thatfew lobsters in the legal size classes escape thefishery each year.

Reductions in abundance and mean size oflobsters could directly affect prey populations.Robles et al. (1990) found a clear size preference inlobster predation on mussels: larger lobsterspreferred larger mussels. In addition, only lobsters>90 mm CL ate more than 10% of the mussels in theupper 1/3 of the size range presented to them (Robleset al. 1990). Tegner & Levin (1983) did not examinefine scale differences in size, but they found thatlarger lobsters ate a greater total number of urchins,and only the largest lobsters ( 150 mm CL) ate thelargest urchins (>90 mm test diam.). A largeabundance of lobsters was also correlated with a lackof disease in Strongylocentrotus purpuratus in a

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1212 New Zealand Journal of Marine and Freshwater Research, 2005, Vol. 39

marine reserve at Anacapa Island (Lafferty &Kushner 2000). Indirect effects on other species mayalso be important. For example, American lobsters(Homarus americanus) can control kelp abundanceindirectly via urchin consumption (Miller et al. 1971;Mann & Breen 1972). Although the indirect effectsof the P. interruptus fisheries on kelp forestcommunities have not been studied, a similar trophiccascade may be present (Harrold & Reed 1985;Pinnegar 2000). The removal of a significant portionof the lobster population, particularly the larger sizeclasses, may have cascading ecological effects thatcould result in functional changes in communitystructure (Davis 1977; Dayton et al. 1989; Estes etal. 1989).

Fishing has been shown to skew the sex ratio inother spiny lobster species (Kelly 2001; Kelly et al.2002). All of the areas we investigated had female-dominated populations in the sub-legal size classes.The sex ratio of the legal-size lobsters was balancedin the INT reserve and recreationally fished areas butmale-dominated in the commercially fished area(Fig. 8). Because reproductive output of malesaffects female clutch size in both Jasus edwardsiiand P. argus (MacDiarmid & Butler 1999), thecombined effect of small size in both sexes andrelatively few females may result in a reduction inreproductive output in P. interruptus. To investigatethis possibility, we applied a size-fecundityrelationship established by Lindberg (1955) to oursize-frequency data. P. interruptus females becomesexually mature between 63.5 and 72 mm CL (Engle1979; Barsky 2001; Vega 2003); therefore, our trapscaught a representative sample of the maturepopulation. Relative fecundity in the recreational andcommercial areas was 83.4% and 42.2%, respec-tively, of the INT reserve. This reduction in fecunditycould affect the ability of the population to sustainitself or other populations, depending on larvalsources and sinks, which are not well known (Pringle1986).

Fisheries managers often use fecundity orbiomass estimates, or a combination of both, toevaluate the status of a fishery and to set referencepoints by which to monitor sustainability (e.g.,Liggins et al. 2000). For example, the Australianwestern rock lobster fishery, widely considered oneof the best-managed fisheries in the world, attemptsto maintain stocks at 20% to 25% of virgin biomasslevels (Donohue 1998; Environment Australia2002). The P. interruptus fishery in Baja California,Mexico, set the management reference point at 50%of virgin biomass (Vega et al. 2000). Other lobster

management models incorporate reference pointsbased on yield per recruit (YPR) (Lockhart &Estrella 1997) or spawning potential ratio (SPR)(DiNardo & Wetherall 1999), both of which requirebiomass and fecundity estimates. We estimatedrelative biomass in the recreational and commercialareas at 92.0% and 45.1%, respectively, of the INTreserve. Our biomass and fecundity estimates maybe useful to fisheries managers interested in estab-lishing reference points for P. interruptus inCalifornia.

In the future, it will be important to conduct long-term studies of other lobster populations inCalifornia and to coordinate with research efforts inMexico. Further research on the feeding ecology ofthe largest size classes of lobsters, most abundant inno-take reserves, will shed light on their role in thecommunity. Future work should also take advantageof newly established protected areas in the northernChannel Islands to monitor the effects of theseclosures on lobster populations. Genetic analysis willreveal the connectivity of populations in Mexico andthe United States to determine which populations arelarval sources and sinks. These studies will con-tribute to informed management decisions toconserve the lobster's ecological role as well as thesustainability of the fisheries.

ACKNOWLEDGMENTS

This research was funded by the Offield Family Founda-tion, Avalon, CA, United States. We are grateful foradvice and support provided by Eddie Hernandez, ScottAalbers, Posh Gardiner, Dr Todd Anderson, Dr JackEngle, Dr Marjorie Wonham, Dr Peter Raimondi, DerekSmith, Lauren Garske and the staff at the University ofSouthern California's Wrigley Marine Science Center.Kristine Barsky, John Ugoretz, and Wendy Dunlap (Cali-fornia Department of Fish and Game) generously suppliedus with unpublished log-book data for southern Califor-nia. We thank the Catalina Conservancy Divers for shar-ing their temperature data. We also thank our anonymousreviewers for comments that greatly improved the qual-ity of the manuscript. This is contribution number 233from the University of Southern California's WrigleyMarine Science Center on Santa Catalina Island.

REFERENCES

Barsky KC 2001. California spiny lobster. In: Leet WS,Dewees CM, Klingbeil R, Larson EJ ed. Califor-nia's living marine resources: a status report. Cali-fornia Department of Fish and Game. Pp. 98-100.

Dow

nloa

ded

by [

99.1

06.2

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Iacchei et al.—Catalina spiny lobster fisheries 1213

Blonder BI, Hunt JH, Forcucci D, Lyons WG 1992.Effects of recreational and commercial fishing onspiny lobster abundance at Looe Key NationalMarine Sanctuary. Proceedings of the Gulf ofCaribbean Fisheries Institute 41: 487-491.

Chakravarti I, Laha RG, Roy J 1967. Handbook of Meth-ods of Applied Statistics. Volume I. John Wiley& Sons. Pp. 392-394.

Davis GE 1977. Effects of recreational harvest on a spinylobster, Panulirus argus, population. Bulletin ofMarine Science 27: 223-236.

Dayton PK, Tegner MJ, Edwards PB, Riser KL 1998.Sliding baselines, ghosts, and reduced expecta-tions in kelp forest communities. Ecological Ap-plications 8(2): 309-322.

DiNardo GT, Wetherall JA 1999. Accounting for uncer-tainty in the development of harvest strategies forthe Northwestern Hawaiian Islands lobster trapfishery. ICES Journal of Marine Science 56: 943-951.

DiNardo GT, DeMartini, EE, Haight WR 2002. Esti-mates of lobster handling mortality associatedwith the Northwestern Hawaiian Islands lobster-trap fishery. Fishery Bulletin 100: 128-133.

Donohue K 1998. Western rock lobster management—options and issues. Fisheries Management Paper113. Fisheries Western Australia, Perth. 71 p.

Duffy JM 1973. Status of the California spiny lobsterresource. California Department of Fish and GameMarine Resources Technical Report 10.

Ebert TA, Russell MP 1988. Latitudinal variation in sizestructure of the west coast purple sea urchin: acorrelation with headlands. Limnology and Ocea-nography 33(2): 286-294.

Eggleston DB, Dahlgren CP 2001. Distribution and abun-dance of Caribbean spiny lobster in the Key WestNational Wildlife Refuge: relationship to habitatfeatures and impact of an intensive recreationalfishery. Marine and Freshwater Research 52:1567-1576.

Engle JM 1979. Ecology and growth of juvenile Califor-nia spiny lobster, Panulirus interruptus (Randall).Sea Grant Dissertation Series, USCSC-TD-03-79. 298 p.

Environment Australia 2002. Assessment of the ecologi-cal sustainability and management arrangementsfor the western rock lobster fishery. 49 p.

Estes JA, Duggins DO, Rathbun G 1989. The ecology ofextinctions in kelp forest communities. Conser-vation Biology 3: 252-264.

Frusher SD, Hoenig JM 2001. Impact of lobster size onselectivity of traps for southern rock lobster (Jasusedwardsii). Canadian Journal of Fisheries andAquatic Science 58: 2482-2489.

Gell FR, Roberts CM 2003. The fishery effects of marinereserves and fishery closures. World WildlifeFund—US, Washington, DC 20037, United States.89 p.

Goñi R, Reñones O, Quetglas A 2001. Dynamics of aprotected Western Mediterranean population ofthe European spiny lobster Palinurus elephas(Fabricius, 1787) assessed by trap surveys. Ma-rine and Freshwater Research 52: 1577-1587.

Harrold C, Reed DC 1985. Food availability, sea urchingrazing and kelp forest community structure. Ecol-ogy 66: 1160-1169.

Kelly S 2001. Temporal variation in the movement of thespiny lobster, Jasus edwardsii. Marine and Fresh-water Research 52: 323-331.

Kelly S, Scott D, MacDiarmid AB, Babcock RC 2000.Spiny lobster, Jasus edwardsii, recovery in NewZealand marine reserves. Biological Conserva-tion 92: 359-369.

Kelly S, Scott D, MacDiarmid AB 2002. The value of aspill-over fishery for spiny lobsters around a ma-rine reserve in northern New Zealand. CoastalManagement 30: 155-166.

Lafferty KD, Kushner D 2000. Population regulation ofthe purple sea urchin, Strongylocentrotuspurpuratus, at the California Channel Islands. In:Brown DR, Mitchell KL, Chang HL ed. Proceed-ings of the Fifth California Islands Symposium.Minerals Management Service Publication 99-0038. Pp. 379-381.

Levene H 1960. In: Olkin I et al. ed. Contributions toProbability and Statistics: Essays in Honor ofHarold Hotelling. Stanford University Press. Pp.278-292.

Liggins GW, Scandol JP, Montgomery S, Craig J, MacbethW 2000: An assessment of the NSW eastern rocklobster resource for 2000-2001. New South WalesFisheries Resource Assessment Series 10. 99 p.

Lindberg RG 1955: Growth, population dynamics andfield behavior in the spiny lobster, Panulirus in-terruptus (Randall). University of California Pub-lications in Zoology 59(6): 157-248.

Lockhart F, Estrella B 1997. Amendment 3 to the inter-state fishery management plan for lobster. Fish-ery Management Report No. 29. The AtlanticStates Marine Fisheries Commission. 44 p.

MacDiarmid AB, Butler IV MJ 1999: Sperm economyand limitation in spiny lobsters. Behavioral Ecol-ogy and Sociobiology 46: 14-24.

Mann KH, Breen PA 1972. The relation between lobsterabundance, sea urchins, and kelp beds. Journal ofFisheries Research Board of Canada 29: 603-609.

Dow

nloa

ded

by [

99.1

06.2

42.2

3] a

t 11:

44 2

3 Ja

nuar

y 20

16

1214 New Zealand Journal of Marine and Freshwater Research, 2005, Vol. 39

Miller RJ, Mann KH, Scarratt DJ 1971. Production po-tential of a seaweed-lobster community in easternCanada. Journal of Fisheries Research Board ofCanada 28: 1733-1738.

Odemar MW, Bell RR, Haugen CW, Hardy RA 1975.Draft report on California spiny lobster Panulirusinterruptus (Randall): research with recommen-dations for management. Unpublished report, Cali-fornia Fish and Game Operations ResearchBranch. 98 p.

Pinnegar JK, Polunin NVC, Francour P, Badalamenti F,Chemello R, Harmelin-Vivien ML, Hereu B,Milazzo M, Zabala M, D'anna G, Pipitone C2000. Trophic cascades in benthic marine ecosys-tems: lessons for fisheries and protected-area man-agement. Environmental Conservation 27(2):179-200.

Pringle, JD. 1986: California spiny lobster (Panulirusinterruptus) larval retention and recruitment: areview and synthesis. Canadian Journal of Fish-eries and Aquatic Science 43(11): 2142-2152.

Robles C 1987. Predator foraging characteristics and preypopulation structure on a sheltered shore. Ecol-ogy 68: 1502-1514.

Robles C, Sweetnam D, Eminike J 1990. Lobster preda-tion on mussels: shore-level differences in preyvulnerability and predator preference. Ecology71: 1564-1577.

Smith SJ, Tremblay JM 2002: Fishery-independent trapsurveys of lobsters (Homarus americanus): designconsiderations. Fisheries Research 62: 65-75.

Tegner MJ, Levin LA 1983: Spiny lobsters and sea ur-chins: analysis of a predator-prey interaction. Jour-nal of Experimental Marine Biology and Ecology73: 125-150.

Vega VA 2003: Reproductive strategies of the spinylobster Panulirus interruptus related to the ma-rine environmental variability off central BajaCalifornia, Mexico: management implications.Fisheries Research 65: 123-135.

Vega VA, Gómez RC, Espinoza CG, Sierra RP 2000.Langosta de Baja California Panulirus interrup-tus. In: Arenas PR, Diaz de Leon A ed.Sustentabilidad y pesca responsible en Mexico:evaluación y manejo 1997-1998. InvestigacionPesquera del Pacifico sur Instituto Nacional de laPesca (INP-SEMARNAP). 691 p.

Ziegler PE, Frusher SD, Johnson CR, Gardner C 2002.Catchability of the southern rock lobster Jasusedwardsii. I. Effects of sex, season, and catchhistory. Marine and Freshwater Research 53(8):1143-1148.

Ziegler PE, Frusher SD, Johnson CR 2003. Space-timevariation in catchability of southern rock lobsterJasus edwardsii in Tasmania explained by envi-ronmental, physiological and density-dependentprocesses. Fisheries Research 61: 107-123.

Dow

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ded

by [

99.1

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