The Influence of Mark-Recapture Sampling Effort on Estimates of Rock Lobster Survival.

Five annual capture-mark-recapture surveys on Jasus edwardsii were used to evaluate the effect of sample size and fishing effort on the precision of estimated survival probability. Datasets of different numbers of individual lobsters (ranging from 200 to 1,000 lobsters) were created by random subsampling from each annual survey. This process of random subsampling was also used to create 12 datasets of different levels of effort based on three levels of the number of traps (15, 30 and 50 traps per day) and four levels of the number of sampling-days (2, 4, 6 and 7 days). The most parsimonious Cormack-Jolly-Seber (CJS) model for estimating survival probability shifted from a constant model towards sex-dependent models with increasing sample size and effort. A sample of 500 lobsters or 50 traps used on four consecutive sampling-days was required for obtaining precise survival estimations for males and females, separately. Reduced sampling effort of 30 traps over four sampling days was sufficient if a survival estimate for both sexes combined was sufficient for management of the fishery

Dependency of survival probability (Phi) and recapture probability (p) on sex (g), time (t) and/or sex and time (g*t) in the five top models for combinations of sampling days and number of traps.

<p>General model is Phi(x)p(y) where “x” and “y” have been shown in the following table as (x)/(y).</p

Summary of sampling data.

<p>Summary of sampling data.</p

Survival probability <i>(Phi</i>) and relative standard error (RSE) of lobsters—combined sexes (a) and different sexes (b) (males (○) and females (▲)), estimated by sex-time independent model <i>(Phi(</i>.<i>)p(g))</i> and sex dependent model <i>Phi(g)p(g)</i> respectively, associated with each combination of fishing effort.

<p>Survival probability <i>(Phi</i>) and relative standard error (RSE) of lobsters—combined sexes (a) and different sexes (b) (males (○) and females (▲)), estimated by sex-time independent model <i>(Phi(</i>.<i>)p(g))</i> and sex dependent model <i>Phi(g)p(g)</i> respectively, associated with each combination of fishing effort.</p

Comparison of model performance with increasing sample size.

<p>Comparison of model performance with increasing sample size.</p