Rock Lobster Reproductive Success

Trophia Ltd. was commissioned to examine the available catch sampling data for evidence of changes in the reproductive success of rock lobster populations.

Rock lobsters mate in late spring and early winter and females brood the fertilised eggs through the winter months. Since 1952, there has been a prohibition on the taking of egg bearing (“berried”) females to protect the fertilised eggs. Higher market prices during winter have resulted in most quota being caught at this time of the year. The shift in effort to the winter months combined with the existing prohibition has resulted in an increased proportion of males in the catch (eg. males made up 89% of the catch in CRA 2 in 1998).

There is concern that the high proportion of males in the catch is impacting on the reproductive success of the population. Trophia standardised the available catch sampling data using the proportion of females in berry as an indicator of reproductive success. The model took into account the effects of (i) fishing year, (ii) fishing depth and (iii) time of year on the proportion of mature females in berry.

This project was funded by the New Zealand Rock Lobster Industry Council Ltd.