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Hune M.,Fundacion Ictiologica | Hune M.,Institute Ecologia y Biodiversidad IEB | Vega R.,Institute Fomento Pesquero
Polar Biology | Year: 2016

Diet compositions of Patagonotothen cornucola and Harpagifer bispinis were studied from two localities, one with continental influence in a wind-protected area (Puerto Riquelme) and another with oceanic influence in a wind-exposed area (Puerto Williams). The dietary analysis performed showed intra-specific differences among contrasting intertidal areas, with greater richness and diversity of prey types in fish from Puerto Riquelme than in Puerto Williams. Gammarid amphipods and Tanaidae dominated the diet of P. cornucola and H. bispinis in Puerto Riquelme, whereas the diet of both fish species in Puerto Williams was characterized by the crustacean isopod Exosphaeroma gigas and gammarids. The dietary overlap was quantified using two similarity indexes (Sorensen and Morisita-Horn), and the results obtained revealed a high diet overlap among the species in each locality. Diet composition did not show significant difference between sexes in both species, while P. cornucola from Puerto Riquelme presented significant differences in fish size in the diet, supporting the existence of some food partitioning. Dissolved oxygen and salinity were important factors in the diet variability of P. cornucola and H. bispinis, since both species showed greater richness and diversity of prey types in intertidal areas with higher dissolved oxygen and lower salinity levels (Puerto Riquelme). In conclusion, the dietary patterns of these two sympatric rocky intertidal species in the Patagonian channels and fjords appear to be regulated by the different environmental conditions that influence the availability and abundance of potential prey in the diet. © 2016 Springer-Verlag Berlin Heidelberg Source


Hune M.,Fundacion Ictiologica | Hune M.,Institute Ecologia y Biodiversidad IEB | Vega R.,Institute Fomento Pesquero
Polar Biology | Year: 2015

The black southern cod, Patagonotothen tessellata, is the most important notothenioid fish species in terms of abundance in southern Chilean Patagonia. However, studies on its trophic ecology are scarce. Here we assessed the spatial variation in the diet of P. tessellata between two localities, one with oceanic influence (Staples Strait) and another with continental influence (Puerto Bories). We used permutation analysis combined with non-metric multi-dimensional scaling to evaluate spatial differences in diet. In addition, generalized additive models were used to identify the most significant environmental, biological and spatial predictors of variability in diet. The black southern cod presents spatial differences in diet composition among contrasting environmental localities. The diet in Staples Strait was characterized by the dominance of the polychaete Platynereis australis, whereas diet in Puerto Bories was characterized by crustaceans, mainly ostracods, gammarids and algae, mainly the filamentous green alga Rhizoclonium sp. and the red algae Polysiphonia sp. Diet composition did not show significant difference between sexes, whereas diet of small, medium and large fish differed to some degree. Smaller-sized P. tessellata were most likely to contain food. Salinity and temperature had significant influence on diet variability, suggesting that P. tessellata showed a greater diversity of prey items in environmental conditions with greater temperature and lower salinity. The results provide evidence of two dietary patterns depending on the type of environment in which they are distributed, highlighting the potential role of the environmental variables on the availability and abundance of potential prey and in structuring diet. © 2015, Springer-Verlag Berlin Heidelberg. Source

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