Fishing power, efficiency and selection of gillnets for the shortfin grunt (Microlepidotus brevipinnis Steindachner, 1869), in the southern coast of Jalisco, Mexico

Gillnet selectivity, fishing power and catch efficiency for Microlepidotus brevipinnis (Steindachner, 1869) off Bahia de Navidad, Jalisco, Mexico, were estimated. Field experiments were conducted using gillnets of 7.62 and 8.89 cm of mesh-size, during April 1994 to March 1995. A total of 457 organisms were caught with the 7.62 cm meshsize, and 592 with the 8.89 mesh-size. Results shows gillnet of 8.89 cm mesh size caught 3 cm larger organisms and 110 g more weighted fish than those caught by the 7.62 mesh-size. The 7.62 mesh-size caught 1.9 times organisms and 1.3 more weight than the 7.62 cm mesh-size. Selectivity analysis indicates an optimum length (100% probability of retention) was 27.7 cm TL for the 7.62 mesh-size and 32.3 cm TL for the 8.89 cm mesh-size. The relative efficiency analysis was estimated as relative catchability ratio between nets and it varied in a range of 25% to 39% with fish length.