[MARMAM] new publication of franciscana mortality estimation

Jonatas henrique Prado jonatashenriquef at yahoo.com.br
Mon Apr 15 12:39:37 PDT 2013

Dear colleagues,
We are pleased to announce the publication of
the following paper:
Prado J.H.F., Secchi E.R.
and Kinas P.G. (2013) Article title:
Mark-recapture of the endangered franciscana dolphin (Pontoporia blainvillei)
killed in gillnet fisheries to estimate past bycatch from time series of
stranded carcasses in southern Brazil. Ecological
Indicators. 32: 35–41.
fishery mortality estimates of franciscana based on stranding data are biased
downwards, as only a fraction of the total bycatch ends up ashore. We estimated
the probability of a franciscana inciden-tally killed by the coastal gillnet
fisheries in southern Brazil to wash ashore and used this as a correction
factor to back-calculate fishing related mortality from a dataset of carcasses
collected between 1979 and 1998. From November 2005 to January 2009, 145
franciscanas incidentally killed in nets were tagged and returned to the sea.
Only 11 of the tagged animals were found during beach surveys. Generalized
Linear Models were used to model the probability of a tagged franciscana
reaching the shore as a function of the covariates wave period, wind direction
and intensity, distance from coast and the target species of the fishery. The
target species had a significant effect on the stranding probability. The
stranding prob-ability of a tagged franciscana was higher in the fishery
targeting white croaker (Micropogonias furnieri) (median = 0.105; 95% CI =
0.05–0.18) rather than weakfish (Cynoscion guatucupa) (0.013; 0.0003–0.069). As
the stranding probability estimate for weakfish was imprecise (wide credible
interval) we decided to hind cast the number of franciscanas incidentally
killed for white croaker season only. The corrected esti-mate of franciscana
mortality was approximately 10 times higher than previous estimates based
solely on stranding data. Finally, this novel mark-recapture approach provides
a useful correction factor to reduce the bias in incidental mortality estimates
derived from stranding data.
I hope
you find the article interesting.
Prado and Co-Authors
M.Sc. Jonatas Henrique Fernandes do Prado  
Doutorando do Programa de Pós Graduação em Oceanografia Biológica - FURG - Brasil
Laboratório de Mamíferos Marinhos e Tartarugas Marinhas 
TEL: +55 (53) 81415681/3233 6537
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