Population dynamics and reproductive ecology of the southern calamari in Tasmania
Squid differ from fish in more than just short life span. They also have a relatively long juvenile phase, exponential growth, short spawning periods, spatial and temporal variability in population dynmaics and considerable inter-individual variability. Therefore, existing fish management strategies are unlikely to adequately address the spatial and temporal variability evident in squid populations. This project directly addresses the key areas of squid fisheries research, that is the need to clarify the variability in the life history characteristics in space and time. It will only be through the quantification of this information and the application of modelling techniques that we will be able to determine the appropriate management strategy for squid, eg closures vs limited access vs total allowable catch.
A need for research on Southern Calamari has arisen because the fishery targets sexually mature individuals on the spawning grounds while they are mating and laying eggs. This is a short-lived species (6-8 months) and populations are entirely dependent on successful production of young by each generation. Therefore, we need to determine the impacts of fishing upon adult populations and egg production, which may compromise future recruitment.
Fishers and managers in Tasmania have raised questions about the current status of Southern Calamari stocks, with suggestions that increasing exploitation may place the stocks at high risk of collapse. A number of factors such as the short lifespan, low fecundity, non-overlapping generations and high inter-annual recruitment variability of this species exacerbate the risk. Especially since managing a species with these biological characteristics cannot be based on previous catch history. We need to develop numerical models that can use biological indicators to manage stocks that are vulnerable to recruitment failure given that the primary target is spawning individuals.
The current state of biological and ecological knowledge about Southern Calamary does not allow management decisions to be made to allow this fishery to develop at sustainable levels. Consequently, there is an urgent need to quantify the productivity of Southern Calamari populations and determine which components of the population are fished by different gear types.