Spatio-temporal distribution and target species of longline fisheries off Southeastern/Southern Brazil between 2000 and 2011

Abstract

In the presente study, cluster analysis was performed to classify 1080 interviews with captains of national pelagic longline fleet (2000 to 2011), and 38 trips of the chartered fleet (2003 to 2008), in relation to the composition of species landed. For the national fleet 4 groups were identified: 1 - Albacores, 2 - Blue shark, 3 - Swordfish, and 4 - Dolphinfish. For the chartered fleet 3 groups were identified: 1 - Swordfish, 2 - Blue shark, and 3 - Albacores. The results indicated that part of the national fleet change their strategies according to the availability of the target species and market demand (internal and external). A part of the fleet from Espírito Santo state operates in the region between December and March, exclusively to capture dolphinfish. The chartered fleet differed from the national one as regards the fishing areas of each target species, mainly as regards swordfish and blue shark. Despite the great difference in the data sets, it is evident that both the national and the chartered fleets operated in accordance with their peculiarities and technological development, adopting strategies that optimize catches and net profits per trip.

Spatiotemporal Variability of Target-Species in Tuna and Tuna-Like Fishing in Brazil

“…Actually, blue shark catch levels recorded in BNDA until the late 1990s were close to zero (0), and it reinforces the hypothesis of catch underreporting throughout this period. The increased number of leased longlines reported in the literature and observed in the present study was essential to the formation of a national catch history and EEZ occupation (Hazin and Travassos, 2007;Dias-Neto, 2010;Fiedler et al, 2015). However, once the national fleet is not just Brazilian, the Brazilian fleet gets vulnerable to retaliation imposed by the greatest fishing countries, mainly Japan and Spain, due to its high dependence on foreign vessels (Hazin and Travassos, 2007;Dias-Neto, 2010;Ruffino, 2016).…”

“…Most stocks of these species are overfished or their catch stays within their maximum sustainable limit (Punt et al, 2015;FAO, 2020). The following species are among the main commercial catch targets worldwide: bigeye tuna (Thunnus obesus), albacore tuna (Thunnus alalunga), yellowfin tuna (Thunnus albacares), swordfish (Xiphias gladius) (Arrizabalaga et al, 2015;Pons et al, 2017;Erauskin-Extramiana et al, 2019) and blue shark (Prionace glauca) -which, by the way, is the most often caught elasmobranch through pelagic longline fishery focused on tuna and tuna-like species (Fiedler et al, 2015;Coelho et al, 2018).…”

“…Indices based on clustering methods (e.g., cluster analysis) (Carvalho et al, 2014;Hazin et al, 2014;Fiedler et al, 2015), catch composition (Biseau, 1998;Chang et al, 2011;Hiraoka et al, 2016), and the number of hooks per basket (Chang et al, 2011) have been used to identify targets and fisher intentions concerning fishing trips or operation, worldwide. As well as in the principal component analysis (Winker et al, 2014), spatial imputation methods (Carruthers et al, 2011), factor analysis of spatial dynamics (Thorson et al, 2016), decision-tree approach (Campbell, 2016) and directed the residual mixture model (Okamura et al, 2018).…”

Characterization and comparison of Brazilian and foreign leased pelagic longline fleets in the Southwestern Atlantic Ocean between 2003 and 2014. How different are these fisheries?

“…Both fleets operated virtually on the same water column stratum (Table 1), being different at the depth of the gear, which is related to the fishing strategy adopted by the vessel's skipper. This partially indicates that for the foreign fleet tunas were not the main target species since they are caught in deeper water, as reported in different studies (Hampton et al, 1998;Bigelow et al, 2006;Kanaiwa et al, 2008;Fiedler et al, 2015).…”

“…In 2009, the last foreign vessel ended its operations from this port, and currently only national vessels are active, with a total of 118 vessels registered between 2010 and 2014 (Projeto TAMAR -National Sea Turtle Conservation Program, database). These vessels change their capture strategies throughout the year and even switch to other fisheries, according to the availability of target species and the demand of internal and external markets (Fiedler et al, 2015). In addition, many vessels migrate away from their home ports during certain seasons; for example, during summer months (November to January) there is an increase of vessels from the Itaipava port based out of Itajaí, corresponding to the dolphinfish (Coryphaena hippurus) season which is most productive farther south than Espírito Santo (Dallagnolo & Andrade, 2008;Fiedler et al, 2015).…”