Relationships of body lengths with mouth opening and prey length of nemipterid fishes (Regan, 1913) in the Gulf of Thailand

This study aims to investigate the relationship among total length (TL) of fish with mouth opening namely horizontal opening (MH), vertical opening (VH), mouth area (MA) and fork length (FL) of seven sympatric nemipterid fish species and to know the relationship between total length and consumed prey length of five sympatric species sampled from the Gulf of Thailand in 2015. A total 883 fish were investigated collected from both cruise surveys and fishing port survey. TL was linearly and log-linearly related with both MV and MH for three and four species, respectively. MA's were always the log linear relation of TL and shapes were nearly oval for all species. FL in all TL-FL relationships were proportional to the TL's in all species (r2 = 0.94, P < .01), except for the female N. tambuloides (r2 = 0.84, P < .01). PL increase significantly (P < .05) with predator length for all five species except in pisces prey item for N. nematophorus (P > .5) and in invertebrate prey items for N. tambuloides (P > .5). So, this study clearly confirms that nemipterid fishes of different sizes feed on all different specific prey items according to its own body size and feed according to size class for prey items available nearby.