Bycatch, discards and survival rates in the small‐scale cuttlefish trap fishery on sandy bottoms off the Algarve coast (southern Portugal)

Abstract

This study reports a detailed description of the bycatch, discards and survival rates in the cuttlefish (Sepia officinalis) trap fishery off the Algarve coast (southern Portugal). A total of 86 fishing surveys involving 6,311 cuttlefish traps were performed between May and September from 2009 to 2014. Bycatch species were caught in 1,037 traps (bycatch catchability rate of 16.4%), comprising 1576 individuals with an overall weight of 268.3 kg. During the study period, bycatch CPUEs were 12.5 ind./50 traps and 2.1 kg/50 traps, with bycatch rates of 21.1% by number and 15.9% by weight. Thirty‐four species (89.5% of bycatch taxa) were discarded at sea, corresponding to discard rates of 19.5% by number and 11.1% by weight. The short‐snouted seahorse, Hippocampus hippocampus (L.), was the third most abundant bycatch species (11.6% No.; 0.4% kg) and the second most discarded (12.6% No.; 0.6% kg), being invariably discarded live and undamaged owing its conservation status. This markedly seasonal small‐scale trap fishery constitutes a locally important socio‐economic activity during spring and summer, characterised by low bycatch and discard rates, complemented by high survival rates of discards.

Towards Sustainability: A Framework for Evaluating Portuguese Small-Scale Fisheries

“…With respect to the environmental dimension the data on Portuguese SSFs is fragmented across numerous peer-reviewed publications, owing to the significant diversity in fishing fleets, gear types, targeted species, fishing locations, seasons, and habitats. This aspect limits the ability to perform comparative studies between fisheries and gears given that fishing fleets, gear, target species, locations, seasons, and ecosystems vary greatly, Portuguese fishery data are scattered throughout peer-reviewed publications (e.g., [18,52,53,56,57,[59][60][61][62][63][64][65]67]). These characteristic makes it more challenging to conduct research that compares fishing impacts among fisheries and gears [85,86].…”

“…Regarding indicators on fishing gear performance and their impact on the environment, several academic-related research studies can be found in the literature. For example, studies on the environmental impact of purse seine [52,[56][57][58][59], trammel nets [18,39,[60][61][62][63], bottom trawling [64][65][66], and traps and pots [67] were retrieved.…”

Time and spatial trends in landing per unit of effort as support to fisheries management in a multi-gear coastal fishery

“…The Portuguese multi-gear fleet, operating mainly nets, traps and longlines, account for relatively low bycatch when compared to other fishing activities such as bottom trawling. It generally takes an opportunistic "all species are valuable" approach, discarding only species interdicted or those with no commercial value [24][25][26]. In such conditions, landings and catches are closely related and, in the absence of catch per unit of effort (CPUE), landings per unit of effort (LPUE) are considered as a good proxy for species abundance [19].…”