Growth analysis of the Pacific sierra Scomberomorus sierra in Colima, México

The artisanal fishery of sierra Scomberomorus sierra along the coast of Colima represents 1% of the total catch. From January 2003 to March 2004 morphometric data of 972 organisms and otoliths of 464 specimens were obtained to determine age and growth. Growth study was carried out by two methods: length frequency analysis and study of sagittae and asterisci otoliths. Both methods identified 5 age groups. Growth parameters of von Bertalanffy’s equation were determined by Ford-Walford and Gulland methods and an iteration adjustment, both techniques showed a high determination coefficient, but the second was better between observed and calculated values according to the sum of squared error; the results obtained were: L_¥ = 99.54 cm, K = 0.205, t_o= -0.060. Mean size for each age was: age 0 (less than one) = 1.22 cm, age 1 = 19.47 cm, age 2 = 34.33 cm, age 3 = 46.43 cm, age 4 = 56.29 cm and age 5 = 64.32 cm. Comparisons for this species were made with results from 20 years ago in the same area, using coincident curves test, showing a significant reduction in average length of each age; this may be caused by changes in the fishery or overexploitation, although growth parameters show the opposite trend. S. sierra has a lower L_¥ in Manzanillo than in Mazatlan, which could be explained by climatic, latitudinal differences or due to population’s genetic variations. The allometric index from the weight-length relationship was isometric, 3.031 and longevity of 15 years.