Spawning stock-recruitment relationships and environmental influences on the tiger prawn (Penaeus esculentus) fishery in Exmouth Gulf, Western Australia

Abstract

A stock-recruitment relationship (SRR) between the spring spawning stock levels and the following autumn recruitment has been established for P. esculentus in Exmouth Gulf. The basic SRR fits the data well with the exception of 2 out of the 14 years when particularly severe cyclones occurred. This has been taken into account by using multiple regression techniques to incorporate the amount of rainfall in January and February as variables representing indices of cyclone activity (multiple correlation of 0.97). An hypothesis for the observed positive and negative effects of cyclones on recruit survival has been presented. The relationship between autumn recruitment and resultant spring spawning stock (RSR) later that year and the effects of fishing, measured in effective effort units, has also been established (multiple correlation of 0.94). An examination of the interaction between the SRR and RSR relationships has been reported which suggests that, under average environmental conditions and high levels of effort, recruitment will move towards a new lower equilibrium level. The robustness of the relationships with respect to assumptions involved and potential sources of bias in the variables used have been evaluated and discussed.