Effects of changes in salinity on oxygen and food consumption of the young sub-Antarctic notothenioid Eleginops maclovinus: possible implications of their use of an estuarine habitat

Abstract

Salinity is one of the most important structuring factors in the distribution and bioenergetics of estuarine fishes. The aims of this work were to study the distribution of the sub-Antarctic, eurythermic, euryhaline and coastal notothenioid Eleginops maclovinus in Lapataia estuary (Tierra del Fuego National Park), in relation to salinity conditions, and the effect of salinity on the oxygen consumption of this species. The spread of the mixing zone of Lapataia was studied and physicochemical properties (conductivity, pH, temperature and salinity) were measured. Distribution of E. maclovinus juveniles was investigated principally by electrofishing in the field. Oxygen consumption of absorptive and post-absorptive young-ofthe-year individuals (8-10 cm total length) was analyzed by stop-flow respirometry measurements, performed at three salinities (1, 12 and 30 psu). The intermediate mixing zone is relatively small in this system, showing an extension of *1.5 km upstream from Lapataia Bay. It was found that there was a strong relationship between the mixing zone and the distribution of juveniles of E. maclovinus. No differences were found in the metabolic baseline at different salinities. A punctual feeding provoked a typical SDA response, with a significant higher ingested food and metabolic scope at intermediate salinity (12 psu). An increased scope was reached by increasing the energy intake and not through a decrease in the standard metabolic rate. Under an available food condition, this capacity could result in an increased growth rate at intermediate salinity.

Ocean acidification and seasonal temperature extremes combine to impair the thermal physiology of a sub-Antarctic fish

“…Accordingly, and in good agreement with expected responses for ectotherm organisms with broad latitudinal distributions (Markle and Kozak, 2018), the SMR of juvenile E. maclovinus was significantly affected by increasing exposure temperature and by the interactive effect of temperature and pCO2. The SMR at 10 °C and present-day pCO2 levels in this study were slightly higher than rates previously measured in E. maclovinus by Vanella et al (2012Vanella et al ( , 2017. Such differences could result from different fish body masses between studies.…”

Neutral and adaptive loci reveal fine‐scale population structure in Eleginops maclovinus from north Patagonia

“…For instance, juveniles of E . maclovinus have a faster growth rate in intermediate salinity environments (iso‐osmotic and hyperosmotic; Vargas‐Chacoff et al, 2015 ) and with food availability conditions (Vanella et al, 2017 ). Oxygen consumption as a proxy of metabolisms showed minor changes comparing gill and kidney tissues with liver tissue, suggesting that E .…”

“…maclovinus have a faster growth rate in intermediate salinity environments (iso-osmotic and hyperosmotic; Vargas-Chacoff et al, 2015) and with food availability conditions (Vanella et al, 2017). Oxygen consumption as a proxy of metabolisms showed minor changes comparing gill and kidney tissues with liver tissue, suggesting that studies have shown that E. maclovinus could reorganize components for the intermediary metabolism to respond to climate change (Oyarzún et al, 2017).…”