Reef fishes? trophodynamic between trawled and non-trawled environments

DAVID E. GALVÁN; FUNES MANUELA

Vina del Mar

Congreso; 1th International Conference on the Applications of Stable Isotope Techniques to Ecological Studies (IsoEcol 2018); 2018

Universidad Catolica Andres Bello

Temperate reefs fishes from western Patagonian are long living animals, low energy budget and high site fidelity. They present complex reproduction strategies and low reproduction potential, which make them particularly vulnerable to local impacts. Trawl fisheries impact the environment by removing target animals, producing discards and scrapping the sea bottom: factors that can alter the availability of different preys. We studied the trophodynamics of two reef fishes of Western Patagonia: The Argentine sandperch; Pseudopercis semifasciata and the Argentine sea bass; Acanthistius patachonicus. Previous studies suggested that the sea bass feeds more on soft bottoms preys and less on the water column preys than the sandperch. Also, a broader diet and a bigger foraging range was descripted for the sandperch. Diet features were compared between trawled and non-trawled areas using stable isotope analysis of C and N along an overlapping size range.At trawled areas, isotopic niches were wider (Area Ps: 0.34, Area Ap: 0.64) and more overlapped with each other (0.1) than at non-trawled areas (Area Ps: 0.32, Area Ap: 0.11; niche overlap: 0.04). Trends along body sizes resulted non-significant for the sea bass (p>0.05). The sandperch showed significant trends of δ13C values vs size only at trawled areas (p= 0.004), while trends of δ15N values vs size were significant only at non-trawled areas (p= 0.005).The seabass expanded its trophic diversity at trawled areas which could be a consequence of changes on the availability of soft bottom preys by surface scrapping and/or the usage of discards. Regarding the sandperch, increments on its trophic level are expected as it become bigger. This was met at non-trawled areas while at the opponent site diets were relatively constant through sizes. Trends ind13C values vs sizes could also be reflecting the availability of more benthic preys on impacted environments. Finally, fishes at trawled areas seems to have more similar diets showing less niche partitionningThis is one of a few cases where theorethical changes on trophic features between trawl and non-trawled envirnosments are actually find, and the differences in trophodynamics features between species sets a good scenario to capture its complexity.