Feeding habits and trophic niche of rainbow runner Elagatis bipinnulata in the western and central Pacific Ocean

Possible changes in the feeding habits and trophic niche width of rainbow runner, Elagatis bipinnulata, were investigated using stomach content analysis (SCA) and stable isotope analysis (SIA). A total of 380 samples were collected as bycatch from tuna purse seine in the western and central Pacific Ocean (WCPO) from 2010 to 2015. The results indicated that the prey groups of E. bipinnulata were composed of fish (74.8%, % by frequency of occurrence), crustaceans (7.0%), cephalopods (2.8%), and digestive mucous with prey wreckage (15.4%). The main species found in the stomach was Decapterus macarellus. There was no obvious variation in the nitrogen stable isotope ratios (delta N-15) among fork length (FL) classes when the smallest size group was not considered. In contrast, there was a significant shift in the carbon stable isotope ratios (delta C-13) between individuals < 55 cm FL and > 55 cm FL (p < 0.01). Additionally, the trophic niche width of E. bipinnulata represented by the corrected standard ellipse area (SEAc) indicated that the trophic niches of E. bipinnulata may behave differently in different size classes because of the variance in feeding ecology or prey preferences at 55-65 cm FL.

Automated summary

Possible changes in feeding habits and trophic niche width of rainbow runner were investigated using stomach content analysis and stable isotope analysis. The results indicated that different size classes of rainbow runner may have different feeding ecology and prey preferences.