Diet shifts of Rhizoprionodon terraenovae from the southern Gulf of Mexico: possible scenario by temperature changes

Abstract

The current study examined the stomach contents of the Atlantic sharpnose shark (Rhizoprionodon terraenovae) in the southern Gulf of Mexico during 2015 to understand the relationship between diet and changes in sea surface temperature (SST). Prey-specific index of relative importance (%PSIRI), diet breadth (Bi), trophic level (TrL), and trophic overlap (PERMANOVA) were calculated between sexes, body size, and climatic seasons (dry, rainy and winter storm). The lowest temperature recorded in the area was during February (23.9°C), and the highest was during August (29.1°C). A total of 124 stomachs were analyzed, with 54.84% containing food. The trophic spectrum was composed of 32 identified prey, with demersal fish (Haemulon plumierii; %PSIRI = 22.82) and pelagic fish (Sardinella aurita; %PSIRI = 12.83) being the most important. According to the diet breadth (Bi = 0.002), Costello's graph, and trophic level (TrL = 4.2), R. terraenovae is a specialist tertiary consumer. PERMANOVA indicated significant trophic differences between sexes (F = 32.22; P < 0.05), body size (F = 13.68; P < 0.05), and among climatic seasons (F = 23.86; P < 0.05). Spearman's correlation indicated a negative relationship between the diversity of prey consumed by R. terraenovae and sea surface temperature (r = -0.75; P < 0.05). Therefore, diet for R. terraenovae is associated with SST, allowing for the development of possible scenarios related to climatic phenomena like climate change.