Boat electrofishing survey of fish abundance in the Ohau Channel, Rotorua, in 2013

Hicks, Brendan J.; Bell, Dudley G.; Tana, Raymond

Boat electrofishing survey of fish abundance in the Ohau Channel, Rotorua, in 2013

dc.contributor.author	Hicks, Brendan J.	en_NZ
dc.contributor.author	Bell, Dudley G.	en_NZ
dc.contributor.author	Tana, Raymond	en_NZ
dc.date.accessioned	2019-04-15T00:49:20Z
dc.date.available	2014	en_NZ
dc.date.available	2019-04-15T00:49:20Z
dc.date.issued	2014	en_NZ
dc.description.abstract	The aim of this survey was to provide on-going monitoring of the fish communities and abundance in the Ohau Channel, especially fish species that are taonga to Maori (eels, goldfish, and koura). In the current study we present the findings from the seventh year of sampling (2013) in view of previous surveys using boat electrofishing in the Ohau Channel. We used the University of Waikato's 4.5 m-long, aluminium-hulled electrofishing boat to catch a total of 1,025 fish (20.3 kg) from 11 sites comprising 2,817 lineal m and 11,484 m² in area on 27 November 2013. Common bully were the most abundant fish species (57% of the catch) followed by common smelt (36% of the catch). Goldfish had their highest biomasses in the lower channel, especially at site 10 near Lake Rotoiti (up to 7.25 g m⁻²). Catch per unit effort (CPUE) for common bullies exceeded smelt CPUE at all sites except site 1, reflecting their greater densities. CPUE for rainbow trout was variable between the sites, and greatest at site 3. The abundance of common bullies in 2013 reversed the apparent trend of reducing abundance since these surveys started in 2007. The cause of fluctuating bully abundance is not known, and was not accounted for by water clarity expressed as black disc distance (BDD) or water conductivity. Poor water clarity can reduce the efficiency of electrofishing, but BDD was greater in 2012 than in 2011 when common bully densities were lower. In 2013, the apparent decline in smelt abundance was also reversed, but the relatively inefficient sampling resulting from boat electrofishing for these two species should be considered. The increased goldfish biomass in 2011-2013 arose because of targeted fishing in the excavated side branch, which clearly offers good habitat for goldfish. Removal of goldfish in the previous years may have reduced the density in the excavated side channel (site 11) compared to previous years. In 2013, a shortfin eel was caught, following the first shortfin eel encountered in the Ohau Channel in 2012.
dc.format.mimetype	application/pdf
dc.identifier.citation	Hicks, B. J., Bell, D. G., & Tana, R. (2014). Boat electrofishing survey of fish abundance in the Ohau Channel, Rotorua, in 2013 (ERI report). Hamilton, New Zealand: Environmental Research Institute, Faculty of Science and Engineering, The University of Waikato.	en
dc.identifier.issn	2350-3432	en_NZ
dc.identifier.uri	https://hdl.handle.net/10289/12477
dc.language.iso	en
dc.publisher	Environmental Research Institute, Faculty of Science and Engineering, The University of Waikato	en_NZ
dc.relation.ispartofseries	ERI report
dc.relation.isreplacedby	10289/13006
dc.relation.isreplacedby	https://hdl.handle.net/10289/13006
dc.rights	© 2014 copyright with the author.
dc.title	Boat electrofishing survey of fish abundance in the Ohau Channel, Rotorua, in 2013	en_NZ
dc.type	Report
pubs.commissioning-body	Client report prepared for Bay of Plenty Regional Council	en_NZ
pubs.confidential	false	en_NZ
pubs.elements-id	236456
pubs.organisational-group	/Waikato
pubs.organisational-group	/Waikato/2024 PBRF
pubs.organisational-group	/Waikato/FSEN
pubs.organisational-group	/Waikato/FSEN/2018 PBRF - FSEN
pubs.organisational-group	/Waikato/FSEN/School of Science
pubs.organisational-group	/Waikato/FSEN/School of Science/2018 PBRF - School of Science
pubs.place-of-publication	Hamilton, New Zealand	en_NZ
pubs.publisher-url	http://www.waikato.ac.nz/eri/research/publications	en_NZ
pubs.user.info	Hicks, Brendan (hicksbj@waikato.ac.nz)
uow.relation.series	47
uow.verification.status	verified