NIWA seeks fishers’ help to track 4000 Hauraki snapper

NIWA will begin tagging around 4000 snapper in the inner Hauraki Gulf next week as part of a major study of snapper movements.

31 October 2006

The inner Hauraki Gulf is famed for its snapper, which support a lively recreational fishery right on Auckland’s doorstep. At any one time, up to 400 recreational boats may fish the most popular areas.

To understand why this fishery has stayed so productive, NIWA is launching a major study of snapper movements in the inner Gulf.

NIWA scientists will begin tagging up to 4000 snapper from commercial longliners in early November, when schooling snapper start to move into the inner Gulf from the surrounding area. The fish will be caught, tagged with small plastic ‘streamer’ tags just below their dorsal (upper) fins, and released.

NIWA is seeking the help of recreational and commercial fishers to report any tagged fish they find, along with details of where the fish were caught. In return, the fishers will receive information on where their fish was tagged and will go into a monthly prize draw.

The information will be used to get a picture of snapper movements in the Gulf to understand what makes the population tick and, ultimately, help maintain a productive fishery. In particular, the scientists wish to test an idea about ‘sources’ and ‘sinks’ in this snapper population.

The idea is that hotspots for snapper (and therefore snapper fishers) are actually population ’sinks' – that is, as snapper are caught, their numbers are replenished by snapper moving in to ‘replace’ them from surrounding ’source' areas. ‘The premise is that something about the sink areas makes them more attractive as habitats for snapper than the source areas’, says NIWA scientist Dr Mark Morrison, who is leading the study.

The scientists suspect that such ecological patterns are driven by a combination of snapper preferences for more complex seafloor structure (such as shells, rocks, sponges, and worm-tubes), higher current speeds, and more abundant food sources.

The tagging study is being supplemented by night video surveys of snapper sleeping on the seafloor. This will provide information on the abundance and size frequencies of snapper in supposed source and sink areas. ‘Initial results from the Gulf are returning higher numbers of snapper in the supposed sink areas, as well as more complex seafloor habitats, than in source areas,’ says Dr Morrison.

NIWA will also be collecting data on recreational fishing effort and catch estimates from aerial boat counts and boat ramp surveys. This will provide information on how many tags are returned per untagged snapper caught, by area, in order to calculate snapper movement rates between the supposed source and sink areas.

The tagging programme forms part of a wider study investigating the interactions of recreational fishing (in the Hauraki Gulf) and tourism (around the Poor Knights Islands) with their underpinning marine ecosystems, now in its second year. The four-year study is being funded by the Foundation for Science, Research & Technology.

What to do if you find a tagged fish

• Remove the tag, and call 09 375 2050 (this number is written on the tag).
• You will be asked for the number on the tag, where and when you caught the fish (GPS coordinates would be ideal if you have them), whether you caught it over sand or reef, and what its length was.
• You will then be sent a pre-paid, self-addressed envelope in which to return the tag to NIWA.
• Once NIWA has received the tag, you will be entered into our prize draw.

What you can win

There will be a prize draw for a Shimano rod and reel set valued at $300, from Fish City, Albany.