Spatial and Sex-Specific Variation in Growth of Albacore Tuna (Thunnus alalunga) across the South Pacific Ocean

Spatial variation in growth is a common feature of demersal fish populations which often exist as discrete adult sub-populations linked by a pelagic larval stage. However, it remains unclear whether variation in growth occurs at similar spatial scales for populations of highly migratory pelagic species, such as tuna. We examined spatial variation in growth of albacore Thunnus alalunga across 90° of longitude in the South Pacific Ocean from the east coast of Australia to the Pitcairn Islands. Using length-at-age data from a validated ageing method we found evidence for significant variation in length-at-age and growth parameters (L∞ and k) between sexes and across longitudes. Growth trajectories were similar between sexes up until four years of age, after which the length-at-age for males was, on average, greater than that for females. Males reached an average maximum size more than 8 cm larger than females. Length-at-age and growth parameters were consistently greater at more easterly longitudes than at westerly longitudes for both females and males. Our results provide strong evidence that finer spatial structure exists within the South Pacific albacore stock and raises the question of whether the scale of their “highly migratory” nature should be re-assessed. Future stock assessment models for South Pacific albacore should consider sex-specific growth curves and spatial variation in growth within the stock

Numerical Modelling and Satellite Remote Sensing as Tools for Research and Management of Marine Fishery Resources

This chapter outlines the use of modelled and satellite remote sensing (SRS) data in supporting the research, technology-development and management of marine fishery resources. The value of such methods used in marine fisheries management is emphasized. State of art techniques in fisheries resource management utilizing numerical models, and SRS, separately and jointly, are described here. Numerical models are useful for studying fish and other aquatic invertebrate larval transport. SRS data are used to locate fish stocks, locate areas of reef stress and delineate areas of high productivity in the wake of cyclone paths. Coupling SRS with models helps to manage fishery resources on an ecosystem scale, generate potential fishing zones (PFZ), forecast ocean state (OSF), detect meso-scale features such as eddies and track cyclones threatening coastal resources.Modelled, SRS and in situ data sets in combination can be used in the estimation of potential fishery resources in the exclusive economic zone (EEZ), which in turn can help in fishing fleet management.Hence, there is a huge scope for application of numerical modelling and SRS in marine fisheries research and management