Mathias Hüne

Spatial variation in the diet of Patagonotothen tessellata (Pisces, Nototheniidae) from the fjords and channels of southern Chilean Patagonia

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.

Estructura del ensamble de peces costeros de los canales y fiordos de la zona central de la Patagonia chilena (48º-52ºS)

Resumen es: La costa de la zona central de la Patagonia (48°-52°S) representa un area particular para evaluar la diversidad y estructura del ensamble de peces, a cau...

Egg masses of the Patagonian squid ( Doryteuthis Amerigo gahi ) attached to giant kelp ( Macrocystis pyrifera ) in the sub-Antarctic ecoregion

Egg masses of the Patagonian squid Doryteuthis (Amerigo) gahi attached to giant kelp (Macrocystis pyrifera) in the Magellanic channels of the sub-Antarctic ecoregion in southern South America is documented for the first time. Of seven egg masses observed between 2008 and 2011, one was taken to the laboratory to be analysed and photographed. Comprising long transparent capsules containing eggs, the masses were strongly attached to the stipes of M. pyrifera. This macroalgae is a potentially important economic resource due to its multiple industrial uses; this study shows that it also serves an important ecological role as a spawning substrate for D. gahi.

Feeding habits in two sympatric species of Notothenioidei, Patagonotothen cornucola and Harpagifer bispinis, in the Chilean Patagonian channels and fjords

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.

Trophic relationships of a subtidal fish assemblage in the Francisco Coloane Coastal Marine Protected Area, southern Chilean Patagonia

ABSTRACT A combination of stomach content and nitrogen (δ15N) and carbon (δ13C) stable-isotope analysis was used to assess the trophic interactions and feeding habits of three notothenioid coastal fish (Champsocephalus esox, Patagonotothen tessellata and Patagonotothen cornucola) and one exotic salmon species (Oncorhynchus tschawytscha) with diverse life habits (benthic and benthopelagic) in the Francisco Coloane Coastal Marine Protected Area, southern Chile. The stomach contents of C. esox were mainly fish; those of P. cornucola and O. tschawytscha were crustacean decapods, Munida gregaria. A cluster analysis on isotope data and stable-isotope Bayesian ellipses detected two different predator groups, one with benthopelagic habits (C. esox and O. tshawytscha) and one with benthic habits (P. cornucola and P. tessellata). These results were supported with similar isotopic trophic level of each group. We suggest that the exotic salmon O. tschawytscha is a generalist predator with a broad trophic niche that may compete with the native notothenioid C. esox, as both have equivalent trophic levels with substantial overlap. This preliminary study is the first on trophic relationships of a subtidal fish assemblage within a remote ecosystem of fjords and channels in Chile’s southern Patagonia.

Molluscan assemblages associated with Gigartina beds in the Strait of Magellan and the South Shetland Islands (Antarctica): a comparison of composition and abundance

ABSTRACT In this paper we evaluated the composition and abundance of molluscs associated with beds of the red algae Gigartina, located in the South Shetland Islands (Antarctic Peninsula) and the Strait of Magellan (southern Chile). During the summer season of 2013, samples were obtained by scuba diving using a 0.25 m2 quadrat, arranged randomly within the bed. We extracted a total of 15 quadrats per sampling site. For Antarctic Peninsula beds the most abundant species were the bivalve Lissarca miliaris (233 individuals) and the gastropod Laevilacunaria antarctica (94 individuals), while for Strait of Magellan beds the most abundant species was the polyplacophoran Callochiton puniceus (36 individuals). Comparative analysis between the two molluscan assemblages showed significant differences in the faunal composition between the Antarctic Peninsula and Strait of Magellan (f = 64.474; p = 0.0001). Therefore, molluscs reported in both areas are characteristic of their respective biogeographic area. Finally, Gigartina species play an important role in the formation of patterns of abundance and diversity of the communities associated with them.