8th Colloquium Crustacea Decapoda Mediterranea, 2-6 September 2002, Corfu, Greec

Bernárdez Martí, Cristina

Corgos López-Prado, Antonio

Freire, Juan

Verísimo Amor, Patricia

Repositorio da Universidade da Coruña

 1 Figure 1.  Experimental traps used in the study.  8th Colloquium Crustacea Decapoda Mediterranea 2-6 September 2002, Corfu, Greece  Population dynamics of Maja squinado in the Ría de A Coruña (Galicia, NW Spain), using mark-recapture experiments  Antonio Corgos, Cristina Bernárdez, Patricia Verísimo & Juan Freire   Departamento de Bioloxía Animal, Bioloxía Vexetal e Ecoloxía, Universidade da Coruña, Campus da Zapateira s/n, E-15071 A Coruña, Spain   INTRODUCTION: The spider crab, Maja squinado, has a complex life history and population dynamics, being their main feature the planktonic larval phase, ontogenetic changes in habitat use in postlarval phases, small-scale aggregations, large-scale migrations, and a metapopulation structure comprising a chain of local coastal populations connected by larval dispersal and adult migrations (Freire et al., 2002; González-Gurriarán et al., 2002; Sampedro et al. 1999; unpublished data). The objective of the present study is to estimate the main parameters driving dynamics (growth-at-moult, mortality and recapture rates and local population size) in shallow-water local populations of Maja using mark-recapture experiments. Connectivity among local shallow-water populations and between these and deep-water mating ground populations is also described.   SAMPLING: Monthly samplings were carried out between December 1997 and November 1999 using experimental traps (Fig. 1). The sampling area was the Ría de A Coruña (NW Spain) (Fig. 2). Three shallow water (5-15 m) sampling stations were selected along the ría. Another station was selected in deeper water (25-30 m)  in the central channel of the ría, that constitutes the migration corridor for postpubertal adults. In the inner area of the ría (Bastiagueiro), where the abundance is higher, sampling was performed along a transect in the longitudinal axis of the ría where seven tows were carried out disposing the traps parallel to the coast. Each tow was separated approx. 180 m from each other. SPAIN43ºN42º8º W 7º50 kmA CORUÑAPORTUGALFigure 2. Location and sampling areas in the Ría de A Coruña.  2  Mark-recapture experiments: Crabs were captured, marked and released in the same area. T-bar anchor tags FD 89-SL (Fig. 3), from Floy Tag® (Seattle, Washington, USA), with individual codes were used. The tag was inserted in the base line of the fifth leg, between the cephalothorax and the abdomen. Recaptures were obtained during monthly sampling. Additional recapture data coming from commercial fisheries were used only for the analysis of movements among local populations. During the sampling period a total of 12606 crabs were captured. From these, 9093 were marked and 670 recaptured, what shows a recapture rate of 7.4%.   Growth at moult: 38 of the recaptured crabs had grown. Average growth at moult was 32.4% of the preecdysial size, ranging from 22.9 and 45.7% (table 1). No significative differences were found between sexes or type of moult (prepubertal vs. terminal) (ANCOVA, p>0.05 in both cases).    Conectivity: Two local juvenile populations were found in shallow waters along the ría. The first one, with higher crab abundance, in the inner part (Bastiagueiro), and the second one in the middle part (Canide). No exchange of crabs was observed between both populations (more than 95% were recaptured in the same area were they were marked). Some adult crabs marked in shallow areas were recaptured in the central channel (migration corridor). Two thirds of these were coming from the inner part (Bastiagueiro).  Population dynamics: To obtain population dynamics data, the MARK program (White & Burnham, 1999) with the Cormack-Jolly-Seber model (recaptures only), was used. From the recapture history, monthly survival (f ) and recapture (p) probabilities were estimated. Sexes were Figure 3. T bar anchor tags used in the experiment. Males Females Total Males Females Total TotalPIM Mean 32.65 31.95 32.30 32.86 32.27 32.43 32.38SD 2.66 5.97 4.43 6.88 3.94 4.70 4.54Min 29.88 23.49 23.49 25.95 22.88 22.88 22.88Max 37.49 39.42 39.42 45.71 38.99 45.71 45.71CL min 73.1 76.1 93.7 97.2CL max 112.8 94.3 119.5 130.0N 6 6 12 6 17 23 35Prepubertal moult Terminal moultTable 1. Growth at moult of Maja squinado in the Ría de A Coruña. Percentage of moult increment (PMI) by sex and type of moult.    Model AICc ?  AICc AICc Weights Model Likelihood Num. Par. Deviance{Phi(t) p(.)} 576.24 0.00 0.685 1.00 24 62.03{Phi(.) p(.)} 577.83 1.59 0.309 0.45 2 96.43{Phi(t) p(t)} 586.03 9.79 0.005 0.01 46 48.51{Phi(.) p(t)} 588.88 12.64 0.001 0.00 24 62.03Model AICc ?  AICc AICc Weights Model Likelihood Num. Par. Deviance{Phi(t) p(.)} 576.24 0.00 0.999 1.00 24 62.03Seasonal model 590.95 14.71 0.001 0.00 31 49.13Model AICc ?  AICc AICc Weights Model Likelihood Num. Par. Deviance{Phi(t) p(t)} 330.11 0.00 0.998 1.00 46 18.76{Phi(t) p(.)} 342.73 12.62 0.002 0.00 24 43.77{Phi(.) p(t)} 357.59 27.48 0.000 0.00 24 44.16{Phi(.) p(.)} 366.14 36.03 0.000 0.00 2 85.46Model AICc ?  AICc AICc Weights Model Likelihood Num. Par. Deviance{Phi(t) p(t)} 330.11 0.00 1.000 1.00 46 18.76Seasonal model 366.20 36.10 0.000 0.00 18 52.77ADULT FEMALESADULT MALESTable 2. Mark-recapture models for adults in Bastiagueiro   3 analyzed separately in adults due to differences  in growth and terminal moult and migration timing. Different models were run (Table 2) and classified under the “Akaike Information Criterion”  AIC. In Bastiagueiro, in the case of adults, the best fit was obtained for the model including a variable f  and a constant p for males, and variable f  and p for females. Both sexes were analyzed together for the juveniles, being the best fit for the model with f  and p variable in time, with independence of sex (Table 3).  For the middle-part population (Canide), just juveniles were analyzed due to very low adult captures. In this case, the best fitting model was a f  variable and constant p one, with independence of sex.  In every case, except for Canide, monthly models were compared with seasonal ones, but the last show worse fit in every case. Juvenile survival rates in Bastiaguiero are the highest, confirming this area as an adult production (“source”) area, while in Canide, with a high mortality rate, adult production is almost zero (“sink population”) (Fig.4)   Population size: A first approximation to population size was performed using the Petersen method modified by Seber (1982) to reduce bias in small samples:  N=[(M+1)(C+1)/(R+1)]-1, where M is the number of crabs marked in month 1, C the total number of captured crabs in month 2, and R number of marked crabs captured in month 2. N estimates population size at the beggining of the experience. This is a valid method for closed populations, so just consecutive months with no migration, no recruitment and no terminal moult were used to estimate population size. Table 3. Mark-recapture models for juveniles in Bastiagueiro and Canide.   Model AICc ?  AICc AICc Weights Model Likelihood Num. Par. Deviance{Phi(t) p(t)} 3023.00 0 0.99402 1 46 239.04{Phi(.) p(t)} 3034.75 11.75 0.00279 0.0028 24 293.26{Phi(t) p(g*t)} 3035.40 12.391 0.00203 0.002 68 204.59{Phi(g) p(t)} 3036.60 13.6 0.00111 0.0011 25 293.10{Phi(g*t) p(t)} 3043.81 20.808 0.00003 0 69 213.01{Phi(g) p(g*t)} 3044.68 21.678 0.00002 0 48 254.63{Phi(.) p(g*t)} 3046.74 23.739 0.00001 0 47 258.72{Phi(g*t) p(g*t)} 3055.17 32.166 0 0 92 183.35{Phi(t) p(.)} 3081.05 58.047 0 0 24 339.56{Phi(t) p(g)} 3082.34 59.34 0 0 25 338.84{Phi(g*t) p(g)} 3098.13 75.128 0 0 48 308.08{Phi(g*t) p(.)} 3100.91 77.903 0 0 47 312.88{Phi(g) p(g)} 3245.32 222.32 0 0 4 544.01{Phi(.) p(.)} 3246.99 223.99 0 0 2 549.69{Phi(.) p(g)} 3247.65 224.65 0 0 3 548.35{Phi(g) p(.)} 3248.88 225.88 0 0 3 549.58Model AICc ?  AICc AICc Weights Model Likelihood Num. Par. Deviance{Phi(t) p(t)} 3023.00 0.00 1.000 1.000 46 139.25{Seasonal model}3111.72 88.72 0.000 0.000 16 286.55Model AICc ?  AICc AICc Weights Model Likelihood Num. Par. Deviance{Phi(t) p(.)} 418.94 0.00 0.224 1.00 24 47.54{Phi(.) p(.)} 419.54 0.61 0.165 0.74 2 84.65{Phi(t) p(g)} 419.79 0.85 0.146 0.65 25 46.34{Phi(g) p(.)} 419.90 0.96 0.138 0.62 3 83.00{Phi(t) p(t)} 419.92 0.98 0.137 0.61 46 36.17{Phi(.) p(g)} 420.05 1.11 0.128 0.57 3 83.16{Phi(g) p(g)} 421.85 2.91 0.052 0.23 4 82.95{Phi(t) p(g*t)} 427.20 8.26 0.004 0.02 69 22.66{Phi(.) p(t)} 427.64 8.70 0.003 0.01 24 48.02{Phi(g) p(t)} 428.49 9.56 0.002 0.01 25 46.81{Phi(g*t) p(t)} 430.05 11.11 0.001 0.00 69 17.12{Phi(g*t) p(.)} 433.27 14.33 0.000 0.00 47 28.73{Phi(g*t) p(g)} 434.84 15.90 0.000 0.00 48 28.21{Phi(g*t) p(g*t)} 441.79 22.85 0.000 0.00 92 16.19{Phi(.) p(g*t)} 461.40 42.46 0.000 0.00 47 33.69{Phi(g) p(g*t)} 463.52 44.58 0.000 0.00 48 33.69JUVENILES INNER AREA (Bastiagueiro)JUVENILES MIDDLE AREA (Canide) 4    Adult males and females were separately analyzed. As seen in table 4, juvenile population size is remarkably larger than adult, and also the inner part larger than the middle one (Canide) that correlates with the higher mortality rates occurring in Canide.    Literature cited:  Freire J, C Bernárdez, A Corgos, L Fernández, E González-Gurriarán, MP Sampedro & P Verísimo (2002). Management strategies for sustainable Juveniles Oct 98 Nov 98 Oct 99 Nov 98 Dec 99 Oct 99M 195 407 359 185 168 174C 498 354 595 180 127 200R 7 5 10 5 3 3N 12,225 24,139 19,504 5,610 5,407 8,793IC 95% - 6,623 48,767 33,932 11,334 11,898 19,347IC 95% + 22,824 11,894 11,514 2,764 2,376 3,864Inner area (Bastiagueiro) Middle area (Canide)Adults Jul 98 Jul 99 Aug 98 Aug 99M 137 91 155 54C 213 155 258 383R 13 9 6 7N 2,108 1,434 5,771 2,639IC 95% - 1,320 807 2,924 1,429IC 95% + 3,841 2,628 11,182 4,928FemalesMalesTable 4. Estimated population size (N) and 95% Poisson confidence interval of juveniles (left) and adults (right) of Maja squinado in the Ría de A Coruña. M, number of individuals marked in the first sample; C, total number of individuals captured in the second sample; R, number of marked individuals in the second sample. Survival probability0.00.20.40.60.81.0Dec 97Jan 98 FebMarAprMayJunJulAugSep OctNovDecJan 99 FebMarAprMayJunJulAugSep OctNovBastiagueiroCanide Juveniles Recapture probability0.00.10.20.30.40.5Dec 97Jan 98 FebMarAprMayJunJulAugSep OctNovDecJan 99 FebMarAprMayJunJulAugSep OctNovBastiagueiroCanideJuveniles Recapture probability0.00.20.40.60.81.0Apr 98MayJunJulAugSep OctNovDecApr 99MayJunJulAugSep OctNovMalesFemalesAdultsSurvival probability0.00.20.40.60.81.0Apr 98 MayJunJulAugSep OctNovDecApr 99 MayJunJulAugSep OctNovMalesFemalesAdultsFigure 4. Parameter estimates of survival rate (f) and probability of recapture (p) for the best fitted models of  Maja squinado in the Ría de A Coruña.  5 invertebrate fisheries in coastal ecosystems of Galicia (NW Spain). Aquatic Ecology 36: 41-50.  González-Gurriarán, E.,  J. Freire & C. Bernárdez (2002). Migratory patterns in the spider crab Maja squinado using electronic tags and telemetry. Journal of Crustacean Biology  22 (1): 91-97.  Sampedro, M.P., E.G. Gurriarán, J. Freire & R. Muiño (1999). Morphometry and sexual maturity in the spider crab Maja squinado (Decapoda: Majidae) in Galicia, Spain. Journal of Crustacean Biology 19 (3): 578-592.  Seber, G. A. F. 1982. The estimation of animal abundance, 2nd edition. Charles Griffin and Company. London.   White, G. C., K. P. Burnham. 1999. Program MARK: Survival estimation from populations of marked animals. Bird study (46) supplement, 120-138.   

Population dynamics of "Maja squinado" in the Ría de A Coruña
(Galicia, NW Spain), using mark-recapture experiments

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Population dynamics of "Maja squinado" in the Ría de A Coruña (Galicia, NW Spain), using mark-recapture experiments

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