Eulerian Approach to the Estimation of Growth Rates and Population Structure of Jumbo Squid ( Dosidicus gigas) in the Central Gulf of California

An Eulerian approach was applied through a daily data set (n¼ 51) on mantle length frequencies of jumbo squid Dosidicus gigas derived from a small jigging fleet (5 vessels), which stayed fishing in the same area off Mulege´, central Gulf of California. Data were corrected for observation bias introduced by the fishing gear (jigs) and were used to analyze population structure and growth-related parameters by modal progression analysis. Sexual maturity stages and size structure showed a predominance of medium-size immature specimens, both male and female. Mean size of jumbo squid showed a progressive increment throughout the fishing period that could be associated with growth or migration. Our estimations of growth rates were higher (3.15–3.85 mm/day) than those calculated previously for D. gigas with other methods in the same region (Gulf of California). This apparent overestimation of growth rates could be associated with a bias introduced by migration. In fact, our study area is part of some migratory routes known for this species and could be considered a transitory feeding ground for medium-size jumbo squid. The most possible explanation for the progressive increment of size (mantle length) during the fishing period considers a dynamic interaction between growth and migration