Incidental catches of franciscana in coastal gillnet fisheries in the Franciscana Management Area III: period 1999-2000

Abstract

-Bycatch of franciscanas in fishing operations along the western South Atlantic Ocean has been observed for approximately 60 years. Reports on bycatch in shark gillnet fisheries off Uruguay date back to the early 1940s. A decade later, gillnet fisheries for bottom-dwelling fish became the major conservation concern for franciscanas in both Brazil and Argentina. A small portion (c. 10%), of the coastal gillnet fleet which operate from the port of Rio Grande (southern Rio Grande do Sul, Brazil) was monitored in 1999-2000. The total annual bycatch was estimated to be 946 franciscanas (non-parametric CI = 467 -1525) for the year 1999 and 719 (non-parametric CI = CI: 248 -1413) dolphins for 2000. The total bycatch for the whole FMA III was 1106 (CI: 578 -1915) for 1999 and 992 (CI: 475 -1832) for 2000. Since data were not normally distributed confidence intervals were estimated by non-parametric bootstrap. Despite strong evidence of decline for the stock from FMA III, no mitigation strategy has been established or designed. Instead, fishing effort is still very high, it is increasing and bycatch is uncontrolled. Thus, prompt management action is required. Regulation of gillnet fishing effort might be the only suitable immediate action to mitigate the bycatch.Resumo -Capturas acidentais de toninhas em operações de pesca têm sido observadas por aproximadamente 60 anos ao longo de sua distribuição no Atlântico Sul-Ocidental. Em águas uruguaias, os registros de capturas nas redes de emalhe, usadas na pesca de tubarões, datam do início dos anos 40. Uma década mais tarde, a pescaria de peixes demersais com redes de emalhe tornou-se a principal preocupação em relação à conservação da espécie tanto no Brasil como na Argentina. Em 1999 e 2000, monitorou-se uma pequena parcela (c. 10%) da frota costeira que opera com redes de emalhe na costa sul do Rio Grande do Sul, Brasil. Estimou-se uma captura acidental anual de 946 toninhas (I.C. não-paramétrico = 248 -1423) para o ano de 1999 e de 719 toninhas (I.C. não-paramétrico = 248 -1423) para o ano de 2000. A captura acidental anual para toda a FMA III (FMA: Área de Manejo para a Toninha) foi estimada em 1106 (I.C. = 578 -1915) e 992 (I.C. = 475 -1832) toninhas em 1999 e 2000, respectivamente. Os intervalos de confiança foram estimados através de procedimentos de "bootstrap" não-paramétrico, visto que os dados não apresentavam distribuição normal. Até o presente, nenhuma estratégia mitigatória foi implementada ou elaborada, apesar das fortes evidências que o estoque da FMA III está declinando. Além disso, o esforço pesqueiro continua elevado, crescendo e as capturas acidentais sem controle. Ações de manejo pesqueiro são urgentemente necessárias. Talvez, a regulamentação do esforço de pesca seja a única atitude imediata aplicável e com chances de ser eficiente.

Decreasing population trend in coastal bottlenose dolphin (Tursiops truncatus) from the Gulf of Guayaquil, Ecuador

“…It is unknown whether by‐caught animals corresponded to the coastal or the offshore ecoptype or both. Bycatch has been identified elsewhere as the major threat for coastal bottlenose dolphins (Hammond et al, 2012; Reeves et al, 2003) as well as for other coastal/estuarine cetacean species around the world such as the Indian Ocean bottlenose dolphin Tursiops aduncus (Kiszka et al, 2008), the Indo‐Pacific humpback dolphins Sousa chinensis (Kiszka et al, ; Ross et al, ) and the franciscana dolphin Pontoporia blainvillei in the south‐western Atlantic (Negri, Denuncio, Panebianco, & Cappozzo, ; Secchi, Kinas, & Muelbert, ). In most cases management recommendations have been proposed to address unsustainable bycatch rates but largely ignored or not employed effectively.…”

Conflicts between river dolphins (Cetacea: Odontoceti) and fisheries in the Central Amazon: a path toward tragedy?

“…Their justifications for this attitude illustrates the degree to which botos are extremely disliked, unwanted, or even hated by most fishermen, similar to what happens in Sierra Leone, where manatees, Trichechus senegalensis Link, 1795 (Trichechidae) are considered "pests" because they damage fishing gear (REEVES et al 1988). This conclusion urges new management strategies: focusing educational efforts on the interaction between cetaceans and fishing activities, in conjunction with the active participation of the local players ZOOLOGIA 29 (5): 420-429, October, 2012 (SECCHI et al 2004, ZAPPES et al 2009). In order to preserve local traditional fishing practices while protecting the botos in the Manacapuru region, it is important to develop fishing methods that are less harmful to the cetaceans, in cooperation with local fishermen (IÑÍGUEZ et al 2003).…”

High mortality of adult female Magellanic penguins by gillnet fisheries in southern Brazil

“…During the last decade, the number of penguin strandings along the Brazilian coast has increased (García‐Borboroglu et al, , ; Mäder, Sander, & Casa, ). Concomitantly, the increase in fishing effort (net size and number of boats) by the gillnet fishery in southern Brazil has increased the incidental mortality of various marine megafauna, especially the Franciscana dolphins ( Pontoporia blainvillei ) and green turtles ( Chelonia mydas ) (Monteiro et al, ; Prado, Mattos, Silva, & Secchi, ; Secchi, Kinas, & Muelbert, ). Similar to these megafauna species, penguins are long‐lived and low‐fecundity animals with delayed maturity (Boersma, ).…”