By-catch and discarding practices in five Algarve (southern Portugal) métiers

Abstract

The catches and discards of trawlers, seiners and trammel netters were studied in the Algarve (southern Portugal) using observers onboard commercial ®shing vessels. Species diversity was high, with 236 species recorded as occasionally, frequently or regularly discarded. Mean discard rates per trip were 0.13, 0.20, 0.27, 0.62 and 0.70, respectively, for trammel nets, demersal purse seines, pelagic purse seines, ®sh trawls and crustacean trawls, with high variability in terms of discard volume and discard rate. This was especially so for seiners where from 0 to 100% of the total catch might be discarded. No signi®cant relationships were found between discard quantity or discard rate and characteristics of the ®shing vessels sampled within each me tier (total length, TAB, hp, kW). Based on the above discard rates and the ocial landings, it was estimated that in 1996, Algarve trawlers discarded 9000±13000 tonnes (t) while seiners discarded 5500±8200 t. Discarding practices in these ®sheries are reviewed and the reasons for discarding are presented by species and me tier basis. The results support the need for more studies on the factors contributing to discarding, variability in discard quantities and rates, the fate of discards and their importance to the marine ecosystem, and on ways of reducing by-catch and discarding in these ®sheries.U.S.

Catches of target species and bycatches of an artisanal fishery: The case study of a trammel net fishery in the Portuguese coast

“…Stergiou et al (2006) studied the trammel net catch species composition in southern European waters and concluded that both season and depth strongly affected catch species composition and that trammel net fishing occurs in 'hot spots', which represent essential habitats of the life history of the targeted and associated species. In Portuguese coastal areas some studies on trammel net fisheries and their impacts on sea grounds have been previously conducted, but all of them along the southern coast of Portugal's mainland (Borges et al, 2001;Erzini et al, 1997Erzini et al, , 2002Gonç alves et al, 2007Gonç alves et al, , 2008a.…”

“…This fishing gear is included in various métiers which are characterized by different combinations of mesh sizes, fishing grounds, fishing time, season, markets and consequently target species (e.g. Borges et al, 2001;Stergiou et al, 2006). Thus, trammel net catches along Portuguese coast are composed of a wide range of species, some of them with recognized or expected management problems (e.g.…”

Estimating standardised landings per unit effort for an octopus mixed components fishery

“…According to the analysis performed by Borges et al (2001), O. vulgaris is a species frequently discarded. Nevertheless, it does not appear among those that are discarded in any significant quantities in the same study and in a similar analysis by Erzini et al (2002).…”

Fishery discards and bycatch: solutions for an ecosystem approach to fisheries management?

“…Also, the physical disturbance of the sediment by trawl nets could expose endobenthic organisms which can then be predated by carnivores (Jenkins et al, 2004). However, the effects on ecosystem structure and function (biodiversity, community structure, trophic links) of returning biomass directly to the ecosystem though discarding are not so well known (Dayton et al, 1995;Jennings & Kaiser, 1998;Lindeboom & de Groot, 1998;Hall, 1999;Collie et al, 2000;Kaiser & de Groot, 2000;Borges et al, 2001;Erzini et al, 2002). The effects of discarding on the stability of trophic webs may have negative consequences for commercial stocks due to the disruption of species interactions and cascading effects throughout the trophic chains (Monteiro et al, 2001).…”

“…Knowledge of the impacts of bycatch and discarding at the community and ecosystem levels becomes increasingly necessary in the context of the multispecies and ecosystem-based approaches to fisheries management (Borges et al, 2001).…”