Graduate Thesis Or Dissertation
 

Proposed minimum mesh size for managing the common Chilean hake fishery

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  • An analysis was conducted to estimate the minimum mesh size for managing the common Chilean hake (Merluccius gayi) fishery. Secondary objectives were to establish the selective relationship between mesh size and fish length, to examine growth patterns and related parameters, and to estimate the critical age (or optimum size) at which hake cohorts reach their maximum biomass. Selectivity was estimated from experiments performed on the central coast of Chile using trawls with codends of 60-, 80-, 100-, and 120-mm mesh size. No differences in gear selectivity were found between sexes, thus a common linear relationship was established. The relative growth of hake proved to be allometric for both females and males with little departure from isometry, and was statistically different between sexes. The Brody growth coefficient, k, was estimated for each sex yielding values of 0.1382 for females and 0.3230 for males. Differences in asymptotic weight (Winf = 3,167.77 gr in females, and Winf = 776.23 gr in males) together with minor differences in natural mortality and in the adjusted "age zero", importantly influenced estimates of critical age. The results of critical age determinations were 5.7 years (49.74 cm) for females, and 3.8 years (38.15 cm) for males. To expedite enforcement, and to produce a minimum departure from their respective age optima, a convenient mesh of 110 mm was recommended. This mesh will theoretically retain the hake at 42.22 cm which corresponds to an age of 4.21 years for females, and 4.96 years for males. Additional studies should be carried out to confirm the selective pattern of gears on hake with tunnels and codends of 110 mm mesh size, and to evaluate the variations in catch caused by differences in trawling speeds, trawling time, type of grounds, migratory movements of hake, and other fishing variables.
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file details PavezCarreraPatricio1986.pdf 2017-08-04 Pubblico Scaricare