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An overview of the hooking mortality of elasmobranchs caught in a swordfish pelagic longline fishery in the Atlantic Ocean

Published online by Cambridge University Press:  21 November 2012

Rui Coelho*
Affiliation:
Instituto Português do Mar e da Atmosfera, I.P. (IPMA), Avenida 5 de Outubro s/n, 8700-305 Olhão, Portugal Centro de Ciências do Mar (CCMAR), Universidade do Algarve, Campus de Gambelas FCT Ed.7, 8005-170 Faro, Portugal
Joana Fernandez-Carvalho
Affiliation:
Instituto Português do Mar e da Atmosfera, I.P. (IPMA), Avenida 5 de Outubro s/n, 8700-305 Olhão, Portugal
Pedro G. Lino
Affiliation:
Instituto Português do Mar e da Atmosfera, I.P. (IPMA), Avenida 5 de Outubro s/n, 8700-305 Olhão, Portugal
Miguel N. Santos
Affiliation:
Instituto Português do Mar e da Atmosfera, I.P. (IPMA), Avenida 5 de Outubro s/n, 8700-305 Olhão, Portugal
*
a Corresponding author: rpcoelho@ipma.pt
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Abstract

Hooking (or “at-haulback”) fishing mortality was analysed in elasmobranchs captured by Portuguese longliners targeting swordfish in the Atlantic Ocean. Information was collected by on-board fishery observers who monitored 834 longline fishing sets between August 2008 and December 2011, and recorded information on 36 067 elasmobranch specimens from 21 different taxa. The hooking mortality proportions were species-specific, with some species having relatively high percentages of live specimens at time of haulback (e.g., blue shark, crocodile shark, pelagic stingray, manta, devil and eagle rays), while others had higher percentages of dead specimens (e.g., smooth hammerhead, silky shark, bigeye thresher). For the most captured species (Prionace glauca, Pseudocarcharias kamoharai, Isurus oxyrinchus and Alopias superciliosus), logistic generalized linear models (GLMs) were carried out to compare the mortality rates between sexes, specimen sizes and the regions of operation of the fleet. The sex-specific proportions of hooking mortality were significantly different for blue and crocodile sharks, with the males of both species having higher proportions of hooking mortality than the females. Specimen size was significant for predicting the hooking mortality for blue and shortfin mako sharks: in both cases, the larger specimens had lower odds of dying due to the fishing process. There were differences in the hooking mortality depending on the region of operation of the fleet, but those differences were also species-specific. For blue and crocodile sharks, the hooking mortality was higher in the Equatorial and southern Atlantic areas (when compared to the NE Atlantic region), while the opposite was observed for the shortfin mako, with lower mortality rates in the NE tropical area compared with the other regions. The results presented in this paper can be integrated into future ecological risk assessment analysis for pelagic elasmobranchs. Furthermore, the new information can be used to evaluate the impact of recent recommendations prohibiting the retention of some vulnerable elasmobranch species.

Type
Research Article
Copyright
© EDP Sciences, IFREMER, IRD 2012

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References

Afonso, A.S., Hazin, F.H.V., Carvalho, F., Pacheco, J.C., Hazin, H., Kerstetter, D.W., Murie, D., Burgess, G.H. 2011, Fishing gear modifications to reduce elasmobranch mortality in pelagic and bottom longline fisheries off Northeast Brazil. Fish. Res. 108, 336343. CrossRefGoogle Scholar
Arrizabalaga, H., Bruyn, P., Diaz, G.A., Murua, H., Chavance, P., Delgado de Molina, A., Gaertner, D., Ariz, J., Ruiz, J., Kell, L.T., 2011, Productivity and susceptibility analysis for species caught in Atlantic tuna fisheries. Aquat. Living Resour. 24, 112. CrossRefGoogle Scholar
Buencuerpo, V., Rios, S., Moron, J., 1998, Pelagic sharks associated with the swordfish, Xiphias gladius, fishery in the eastern North Atlantic Ocean and the Strait of Gibraltar. Fish. Bull. 96, 667685. Google Scholar
Campana, S.E., Joyce, W., Manning, M.J., 2009, Bycatch and discard mortality in commercially caught blue sharks Prionace glauca assessed using archival satellite pop-up tags. Mar. Ecol. Prog. Ser. 387, 241253. CrossRefGoogle Scholar
Carruthers, E.H., Schneider, D.C., Neilson, J.D., 2009, Estimating the odds of survival and identifying mitigation opportunities for common bycatch in pelagic longline fisheries. Biol. Conserv. 142, 26202630. CrossRefGoogle Scholar
Coelho, R., Santos, M.N., Amorim, S., 2012, Effects of hook and bait on targeted and bycatch fishes in an equatorial Atlantic pelagic longline fishery. Bull. Mar. Sci. 88, 449467. CrossRefGoogle Scholar
Cortés, E., Arocha, F., Beerkircher, L., Carvalho, F., Domingo, A., Heupel, M., Holtzhausen, H., Santos, M.N., Ribera, M., Simpfendorfer, C., 2010, Ecological risk assessment of pelagic sharks caught in Atlantic pelagic longline fisheries. Aquat. Living Resour. 23, 2534. CrossRefGoogle Scholar
Diaz, G.A., Serafy, J.E., 2005, Longline-caught blue shark (Prionace glauca) : factors affecting the numbers available. Fish. Bull. 103, 720724. Google Scholar
Dulvy, N.K., Baum, J.K., Clarke, S., Compagno, L.J.V., Cortés, E., Domingo, A., Fordham, S., Fowler, S., Francis, M.P., Gibson, C., Martinéz, J., Musick, J.A., Soldo, A., Stevens, J.D., Valenti, S., 2008, You can swim but you can’t hide : the global status and conservation of oceanic pelagic sharks and rays. Aquat. Conserv. Mar. Freshw. Ecosyst. 18, 459482. CrossRefGoogle Scholar
Enever, R., Catchpole, T.L., Ellis, J.R., Grant, A., 2009, The survival of skates (Rajidae) caught by demersal trawlers fishing in UK waters. Fish. Res. 97, 7276. CrossRefGoogle Scholar
Hastie T., 2011, gam : generalized additive models. R package version 1.04.1. http://CRAN.R-project.org/package=gam.
ICCAT, 2009, Recommendation by ICCAT on the conservation of thresher sharks caught in association with fisheries in the ICCAT convention area. ICCAT Recommendation 2009-07. URL : http://www.iccat.es/Documents/Recs/compendiopdf-e/2009-07-e.pdf.
ICCAT, 2010a, Recommendation by ICCAT on the conservation of oceanic whitetip shark caught in association with fisheries in the ICCAT convention area. ICCAT Recommendation 2010-07. URL : http://www.iccat.es/Documents/Recs/compendiopdf-e/2010-07-e.pdf.
ICCAT, 2010b, Recommendation by ICCAT on hammerhead sharks (family Sphyrnidae) caught in association with fisheries managed by ICCAT. ICCAT Recommendation 2010-08. URL : http://www.iccat.es/Documents/Recs/compendiopdf-e/2010-08-e.pdf.
ICCAT, 2011, Recommendation by ICCAT on the conservation of silky sharks caught in association with ICCAT fisheries ICCAT Recommendation 2011-08.
Mandelman, J.W., Farrington, M.A., 2007, The estimated short-term discard mortality of a trawled elasmobranch, the spiny dogfish (Squalus acanthias). Fish. Res. 83, 238245. CrossRefGoogle Scholar
Morgan, A., Burgess, G.H., 2007, At-vessel fishing mortality for six species of sharks caught in the northwest Atlantic and Gulf of Mexico. Gulf Carib. Res. 19, 123129. Google Scholar
Morgan, A., Carlson, J.K., 2010, Capture time, size and hooking mortality of bottom longline-caught sharks. Fish. Res. 101, 3237. CrossRefGoogle Scholar
Moyes, C.D., Fragoso, N., Musyl, M.K., Brill, R.W., 2006, Predicting postrelease survival in large pelagic fish. Trans. Am. Fish. Soc. 135, 13891397. CrossRefGoogle Scholar
Musyl, M.K., Moyes, C.D., Brill, R.W., Fragoso, N.M., 2009, Factors influencing mortality estimates in post-release survival studies. Mar. Ecol. Prog. Ser. 396, 157159. CrossRefGoogle Scholar
Musyl, M.K., Brill, R.W., Curran, D.S., Fragoso, N.M., McNaughton, L.M., Nielsen, A., Kikkawa, B.S., Moyes, C.D., 2011, Postrelease survival, vertical and horizontal movements, and thermal habitats of five species of pelagic sharks in the central Pacific Ocean. Fish. Bull. 109, 341368. Google Scholar
Petersen, S.L., Honig, M.B., Ryan, P.G., Underhill, L.G., Compagno, L.J.V., 2009, Pelagic shark by-catch in the tuna- and swordfish-directed longline fishery off southern Africa. Afr. J. Mar. Sci. 31, 215225. CrossRefGoogle Scholar
R Development Core Team, 2011, R : A language and environment for statistical computing. Version 2.13.0. R Foundation for Statistical Computing, Vienna, Austria. http://www.R-project.org.
Rodriguez-Cabello, C., Fernández, A., Olaso, I., Sánchez, F., 2005, Survival of small-spotted catshark (Scyliorhinus canicula) discarded by trawlers in the Cantabrian Sea. J. Mar. Biol. Assoc. UK 85, 11451150. CrossRefGoogle Scholar
Smith, S.E., Au, D.W., Show, C., 1998, Intrinsic rebound potentials of 26 species of Pacific sharks. Mar. Freshw. Res. 49, 663678. CrossRefGoogle Scholar
Stevens, J.D., Bonfil, R., Dulvy, N.K., Walker, P.A., 2000, The effects of fishing on sharks, rays, and chimaeras (Chondrichthyans), and the implications for marine ecosystems. ICES J. Mar. Sci. 57, 476494. CrossRefGoogle Scholar
Walsh, W.A., Bigelow, K.A., Sender, K.L., 2009, Decreases in shark catches and mortality in the Hawaii-based longline fishery as documented by fishery observers. Mar. Coast. Fish. 1, 270282. CrossRefGoogle Scholar
Warnes G.R., Bolker B., Lumley T., Johnson R.C., 2011, gmodels : Various R programming tools for model fitting. R package version 2.15.1. http://CRAN.R-project.org/package=gmodels.