Thesis

Age, growth, and batch fecundity of gulf corvina, Cynoscion othonopterus

The Gulf Conrina, Cynoscion othonopterus, is a vital component of commercial fisheries in the northern Gulf of California, yet little is known about its life history. 516 specimens were collected from the commercial gillnet fishery at the Gulf of Santa Clara and El Indivisio in Sonora, Mexico from March 2009 to May 2010 to determine the age structure, growth rate, and batch fecundity of adults. Fish ranged from 145 mm to 1013 mm in total length and from 1 to 8 years of age. Yon Bertalanffy growth models were estimated two ways, using all samples and using mean length-at-age for each age class for the population, and for males and females separately. Mean oocyte diameter differed significantly among development stages. Spawning females produced up to 1,219,342 oocytes per batch, and batch fecundity was correlated to both total length and gonad-free body weight. The growth rate of C. othonopterus differed between sexes with males having a higher growth rate earlier in life and females reaching a larger size. The distribution of oocyte diameters and oocyte stages indicate that C. othonopterus are synchronous. Multiple batch spawners with indete1minate annual fecundity. The high degree of synchronization in gonadal development among females reflects the semi-lunar spawning cycle of adults, which migrate to spawn in the estuaries of the Colorado River Delta over four day periods during six consecutive spring tides.

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