Fish functional diversity as an indicator of resilience to industrial fishing in Patagonia Argentina

Abstract

The relationship between fish functional diversity and fishing levels at which its baselines shift is important to identify the consequences of fishing in ecosystem functioning. For the first time, we implemented a trait-based approach in the Argentine Patagonian sea to identify the vulnerability and spatiotemporal changes in functional diversity of fish assemblages bycatch by a trawling fleet targeting the Argentine red shrimp Pleoticus muelleri (Spence Bate, 1888) between 2003 and 2014. We coupled seven fish trophic traits to a reconstructed fish assemblage for the study area and bycatch and evaluated changes in fish species richness and four complementary functional diversity metrics [functional richness, redundancy, dispersion, and community trait values] along with fishing intensity, temporal use, latitudinal location, and depth of fishing grounds. Resident fishes larger than 30 cm in TL, with depressed and fusiform bodies, intermediate to high trophic levels, and feeding in shallow benthic, benthodemersal, and benthopelagic areas were vulnerable to bycatch. Fish assemblages exhibited a low functional trait redundancy, likely related to species influxes in a biogeographic ecotone with tropicalisation signs. Significantly increases in fish trait richness and dispersion polewards and with depth suggested new functional roles in these grounds, matching trends in community body size, reproductive load, maximum depth, trophic level, and diet breadth. Finally, a temporal increase in fish species and functional trait removal in fishing grounds led to trait homogenisation since the first year of trawling. The identified tipping points in temperate fish functional trait diversity highlight trait-based approaches within ecosystem-based fisheries management.

Temporal change in functional rarity in marine fish assemblages

“…To date, investigations of temporal change in marine ecosystems have focused on single populations [49,50]. However, it is becoming clear that multi-species, assemblage-based analyses [51,52], which include information on functional and taxonomic diversity, and potentially also phylogenetic diversity, will be important in tracking biodiversity change in these systems, predicting their resilience in the face of anthropogenic pressures [53], and in shaping conservation decisions and designing fisheries policy [54–56]. As our investigation has shown, different dimensions of biodiversity change are not necessarily correlated.…”

Parasites as tags for stock identification of a highly exploited vulnerable skate Dipturus brevicaudatus (Chondrichthyes: Rajidae) in the south‐western Atlantic Ocean, a complementary tool for its conservation

“…Beyond those environmental and biological characteristics acting locally to drive the observed discreteness of stocks of D. brevicaudatus , differential fishing pressures can reinforce these patterns. Indeed, this skate is both subject to by‐catch (Ruibal Núñez et al, 2018; Rincón‐Díaz et al, 2021) and targeted by a fishery directed at skates in the northern regions of the Argentine Sea (Colonello & Cortés, 2014), where it suffers the greatest fishing pressure (Sánchez et al, 2011). Conversely, skates from NP were mostly caught by research cruises in a restricted area, imposed to protect juvenile hake (Irusta et al, 2016), where the fishing pressure is lower.…”

“…The longnose skate, Dipturus brevicaudatus (Marini, 1933) is a common component of the by‐catch in several Argentine fisheries (Paesch & Oddone, 2008), regularly occurring in red shrimp and hake fisheries (Estalles et al, 2011; Bovcon et al, 2013; Ruibal Núñez et al, 2018; Rincón‐Díaz et al, 2021). Cedrola, González & Pettovello (2005) reported that D. brevicaudatus is the most frequent accidentally caught skate in the red shrimp fishery operating in the Gulf of San Jorge where it comprises up to 55.6% of by‐catch weight.…”