Geographic differences and annual stability in length-weight relationships of fish mullets (Pisces: Mugilidae)

Resumo

Length-weight relationships are essential in fisheries science since they are used to calculate fish yield. Even though spatial and temporal differences in length-weight relationships are known to exist, it is frequently understood that lengthweight relationships do not vary within near stocks. In order to probe this, we analyze the lengthweight relationships for 384 Mugil cephalus and 652 specimens of M. curema
from commercial captures on two locations of the Mexican Pacific coast and seven along the Gulf of Mexico including the US. In the locations of the Mexican Gulf of Mexico coast contiguous years were sampled. Results show that the parameter b ranged from 2.15 to 3.87 for M. cephalus and from 2.39 to 3.11 for M. curema. No significant differences were found between regions. Even though the b values for M. cephalus
are higher in northern locations (USA samples) while for M. curema b values increase in low latitudes with more tropical characteristics. Most of the results showed negative allometric values, which seems to indicate that commercial captures are mainly represented by young adults. No significant differences between years were detected for both species. Plot of log a vs b showed no significant differences between
species form pointing out that both are similar-looking with fusiform shape. This resemblance demonstrates that the species of the genus Mugil are characterized by much conserved morphological features, which noticeably obstruct taxonomic determination.