Fish Surveys at Poor Knights show Good Results

26 June 2000

Fish Surveys at Poor Knights show Good Results

A draft report on the monitoring of selected fish species at the Poor Knights Islands Marine Reserve has come up with very encouraging results showing snapper, tarakihi and pink maomao numbers to have increased in both size and abundance.

The changes were recorded between surveys carried out in September 1998 and again in March and September 1999 when full marine reserve status had been reinstated at the Poor Knights Islands Marine Reserve.

This Department of Conservation-commissioned report forms part of an intensive monitoring and research project looking into the effects of full marine reserve status on fish species at the Poor Knights Islands Marine Reserve

The Poor Knights Marine Reserve was closed to all fishing in October 1998 following a number of years during which a fishing notice allowed limited fishing using specified techniques in certain parts of the reserve. It is now illegal to fish anywhere within 800 metres of any of the Poor Knights Islands and associated rocks and stacks.

One of the report’s authors, Leigh Marine Laboratory-based scientist Trevor Willis, said the three reef-associated species known to have been targeted by anglers while fishing was still allowed at the reserve, were surveyed as part of the research.

The fish surveys were carried out in September 1998 when certain types of fishing were still permitted in parts of the Reserve and again in March and September 1999 when full Marine Reserve status was in place at the Poor Knights.

Relatively low numbers of snapper were detected in the September 1998 survey, but 18 months after complete closure an annual three fold increase was measured. Tarakihi also recovered to twice their density of pre-Marine Reserve times.

Mr Willis said the results showed snapper, tarakihi and pink maomao had recolonised the shallow reef areas around the Poor Knights at a surprising rate although this could be partly explained by seasonal fish movements and the underwater topography of the areas.

However, he said that it is extremely unlikely that such marked increases would have been observed if fishing still continued at the Poor Knights.

To further measure the changes, reference sites were also set up at the Mokohinau Islands located east of the Hen and Chickens Islands and at Cape Brett where fishing is permitted.

Reference sites enable allowances to be made for other natural changes occurring in the sea that should be common to both the treatment and control sites.

The research was carried out using a sophisticated baited underwater video camera that enabled surveys of fish numbers to be undertaken at greater depths than could be done using divers.

Survey work in shallower depths was done, however, using divers doing visual counts.

Mr Willis said the survey work was providing important scientific data regarding the abundance of certain fish over time and in various sections of the reserve.

Ecological studies of reef fish abundance, largely based on divers’ observations have been carried out intermittently at the Poor Knights since 1978. No single study or groups of study provided enough detailed information assessing the impacts of recreational fishing on reef fish ecology had, however, been undertaken.

The draft report is being prepared for peer review before DOC can formally accept its results.

Mr Willis said the survey work would continue until 2002.

For more information please contact Trevor Willis on (09) 422 6111

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