Physiological effects of incidental capture and seasonality on juvenile green sea turtles (Chelonia mydas)

Fishery is one of the main threats faced by sea turtles. However, literature relating to the physiological effects of incidental capture by fishing gears is scarce. The aim of this study is to establish blood reference values for a juvenile population of Chelonia mydas, from Ubatuba- Brazil, and compare them with incidental captured animals by fisheries in the same area, considering seasonal variation. Animals were captured during summer and winter, from direct capture (diving) and incidental capture (pound net and gillnet). Blood samples were collected from 96 healthy green sea turtles and, were analyzed for determining levels of glucose, lactate, total protein, uric acid, albumin, total lipids, triglycerides, VLDL cholesterol, total cholesterol, corticosterone concentrations, total antioxidant capacity, and lipid peroxidation. Corticosterone concentrations were significantly lower in animals captured by diving than in those captured by pound net and gillnet and were thought tso more closely represent baseline levels. Thus, the values found in animals captured by diving were used to establish reference values for this population. Turtles captured in summer had a significant increase in blood levels of glucose, total protein, uric acid, albumin, TBARS, and TEAC; and a decrease in total lipids compared with turtles captured in winter. Although pound nets are considered a low impact fishery to the turtles due to the low mortality rates, seven out of twelve parameters differed significantly from baseline values established for the species. Entanglement in gillnets caused greater perturbations than pound net and all parameters analyzed were significantly different from the reference values. These data indicate that incidental capture causes substantial alterations in health parameters of sea turtles. The results obtained in this study would help in future rehabilitation programs of sea turtles that are captured by fisheries. Additionally, reference values can be used for future comparisons with populations of the same species and with unhealthy and stressed individuals.