Evidence of age-class truncation in some exploited marine fish populations in New South Wales, Australia

Abstract

Exploited reef-associated species in south-eastern Australia have evolved life-history strategies to ensure population persistence through periods that are unsuitable for recruitment. They are characterized by considerable potential longevity (20–50 years), sexual maturation at relatively young ages (2–4 years old) and variable recruitment patterns. The age compositions in landings of the major reef-associated species in this region were used to demonstrate that some species have been subjected to significant age-class truncation. Species with long histories of exploitation had age compositions with relatively few fish greater than 5 years old. It is suggested that the removal of older age classes from the most heavily exploited populations has lowered their resilience to environmental change and that remedial management action may be required to rebuild reserves of older individuals. It is argued that the management options that are most likely to succeed in achieving this objective for populations of offshore reef-associated species include reducing rates of exploitation to very low levels, protecting larger/older fish through regulated maximum length limits and/or changes to gear selectivity and no take marine protected areas. The most appropriate management options will depend on the life-history of the species being considered.