Science Centres: Aquatic Biodiversity and Biosecurity

Another new goby species was recently discovered in our nets while sampling in Whangapoua Harbour, Coromandel. The goby did not match anything encountered before from estuaries throughout the northern North Island. Its most striking feature was the many iridescent blue spots along its sides, in contrast to native goby species. Australian Museum expert Dr Doug Hoese indicated that the new fish was Acentrogobius pflaumii, a species from the northwestern Pacific, which is native to Japan, Korea, China (Taiwan), and the Philippines.M

This species of goby is also found in Port Phillip Bay, Victoria, Australia, where it probably arrived via ship ballast water in the early to mid 1990s. It has since spread to other parts of Australia, including Sydney Harbour, and at least one estuarine population is now in New Zealand. We do not know how it got here, but it seems most likely that it came from Australia.

In southern Japan A. pflaumii is found mainly on sandy flats and in Zostera seagrass beds, while in Port Phillip Bay it occurs across large areas of sand and mud. We are still processing our samples from Whangapoua Harbour, but most of the specimens we found came from a small area of mud adjacent to a mangrove forest. It probably arrived here recently because it appears to be confined to this harbour, and, as yet, is not common in the harbour’s large seagrass meadows. We did not find any of these gobies in the summer of 2001 when we took samples from Whangapoua and 24 other northern estuaries, including Whitianga and Tairua.

This is the second invasive goby species now recognised in New Zealand (after the bridled goby). We have previously reported on one other invasive goby – the exquisite goby (Biodiversity Update No. 4, p. 6); however, recent examinations of collections at the Museum of New Zealand suggest that the exquisite goby may be a native species.

The status of another goby found recently in tidal rivers at Great Barrier Island and North Cape is unknown. More exotic gobies could turn up, and we will be keeping a close watch for new species as NIWA’s FRST-funded research on estuarine and coastal fish habitats continues.

We also found a rich and diverse fish assemblage in Whangapoua Harbour, especially in the seagrass meadows in the lower intertidal and immediate subtidal zones. These zones are biodiversity hotspots for juvenile fish, supporting more species and numbers of fish than adjacent, unvegetated sand and mud habitats. Particularly important was our discovery of many juvenile snapper, ranging from those which had recently settled out of the plankton and were about 16–18 mm long to larger juveniles only a few months old. Reports of newly settled snapper are rare, so this discovery has important implications for the management of seagrass habitats, which have been in decline over the last century. We also found large numbers of other juvenile fish, including trevally, parore, and spotties, and smaller numbers of triplefins, gobies, pipefish, garfish, kahawai, gurnard, stargazers, mullets, flounders, and soles.

We still have a lot to learn about how fish species use estuarine and coastal habitats throughout their life cycles, and what we can do to ensure that human activities do not unduly damage these habitats. This ongoing research will improve and expand on our knowledge and help resource managers conserve, and perhaps enhance, these important ecosystems.

Mark Morrison [ m.morrison@niwa.co.nz ]
Crispin Middleton, Cameron Walsh, and Malcolm Francis

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Further sampling has just discovered a second colony of A. pflaumii in Waitemata Harbour, suggesting that the species may be more widespread.