At-risk smelt being put under the microscope
Conservation agencies are pulling their resources together to hunt down an at-risk fish only found in Canterbury rivers..
The native stokell’s smelt is only visibly different to the common smelt under a microscope.
New Zealand Federation of Freshwater Anglers president Dr Peter Trolove said he was concerned that without proper protection, stokell’s could be on the way to being the second species of native fish to become extinct after the southern grayling.
He said the decline of the stokell’s smelt population was largely due to over-irrigation and abstraction in Canterbury’s braided rivers.
‘‘The whole ecology has been destroyed over a matter of years,’’ Trolove said.
Environment Canterbury, Department of Conservation, Te Ru¯ nanga o Arowhenua, and Fish and Game have joined forces to survey the Rangitata, Ashburton and Rakaia rivers.
ECan director of science Dr Tim Davie said that during the last two weeks of November, the organisations conducted surveys of the coastal lagoons that are predominantly freshwater.
‘‘Smelt were one of target fish we were wanting to catch,’’ Davie said.
‘‘We caught smelt in all three ha¯pua[coastal lagoons], but identifying the difference between stokell’s and common smelt is very difficult in the field, as they look very similar. Some samples of smelt have been taken back to the laboratory for identification under the microscope and to be sent away for genetic testing.’’
Davie said the aim of the study was to determine the state and health of the fish communities, and compare the results to surveys in some of Canterbury’s braided river lagoons in the 1980s.
‘‘We hope to revisit the ha¯ pua sampling sites in late summer to resurvey the fish communities and to see if they differ to those seen in November.
‘‘We also hope to carry out similar fish surveys over the next few years on other river ha¯ pua and estuaries throughout Canterbury.’’
Davie said it was too early to determine how much fish communities have changed over the past few decades in the Hakatere/ Ashburton, Rangitata and Rakaia ha¯ pua.
‘‘However, preliminary results suggest that fish abundances and diversity have decreased from levels seen in the 1980s,’’ he said.
Trolove said it was ‘‘absolutely paramount’’ that something was done to improve the state of the smelt fishery.
‘‘They’re absolutely vital not only to the trout fishery, but also the native birds who feed at the braided rivers.
‘‘I remember during the 1990s when the smelt were abundant, and now their population has whittled down to close to nothing. The situation became so serious that I actually spoke to DOC about it,’’ Trolove said.
Fish and Game spokesman Richie Cosgrove said the ha¯ pua were a really important environment for salmon and trout.
‘‘Therefore, we have an interest in making sure they are healthy, which is why we have helped out with staff and boats to help the survey achieve its goals.
‘‘This will give us up to date information on the state of the ha¯ pua that we can compare to the historical information we have for these ha¯pua and see what level of change has occurred,’’ Cosgrove said.
Davie said other fish species caught during the survey included bullies (common, giant and bluegill species), yellow-eyed mullet, longfin and shortfin tuna (eels), torrent fish, adult inanga and whitebait.