Movement, growth and stock assessment of the coastal fish Lichia amia (Teleostei: Carangidae) off the South African coast.
The limited range of garrick/leervis Lichia amia, its popularity as a gamefish to all sectors of the marine recreational linefishery and the degradation of many estuaries which function as nurseries for this species, has aroused concern about the stock status of this species. In addition, other than a preliminary investigation conducted by ORI in 1992, relatively little research has been undertaken on this important recreational species. Considering the recreational value of L. amia and the need to provide a scientific basis for its management, a comprehensive stock assessment was required. This study therefore investigated the biology and stock status of L. amia off the South African coast. Through ad hoc biological sampling undertaken from 1978-2007 and validation of growth by means of OTC marking, the growth of the L. amia population was best described as: Lt=1206mmfl(1-e-20[t+1.10 years]). Growth was also determined using tag-recapture and length frequency data. The tag-recapture data was further utilized in illustrating the movement behaviour of L. amia. Trends in catches were determined from the analysis of catch and effort data from the National Marine Linefish System (NMLS) and Boat Launch Site Monitoring System (BLSMS) databases. This showed a decreasing trend in the CPUE of L. amia along the KZN coast over time for all sectors of the KZN marine recreational linefishery investigated. The growth parameter estimates from the length-at-age data were used in undertaking a per-recruit assessment of L. amia. The results of the spawner-biomass-per-recruit (SBPR) model indicate that L. amia is at 14% of its unfished level. According to the South Africa.s Linefish Management Protocol (LMP), the L. amia stock has thus collapsed and appropriate management options to rebuild the stock are discussed.