Comparison of catch rates and catch composition among ‘research-angler’ diary and fishery-independent survey methods in Victoria, Australia

ABSTRACT

‘Research-angler diary’ (RAD) and fishery-independent survey (FIS) methods were trialled for sampling recreational fish populations of estuary perch (Macquaria colonorum) black bream (Acanthopagrus butcheri), and Murray cod (Maccullochella peelii) in their respective habitats. Catch rates and catch length-frequency distribution were compared based on ‘catchability’ and its components ‘availability’, ‘encounterability’, and ‘selectivity’. The FIS consistently caught significantly more species at much higher numbers than the RAD. Catch rate and length-frequency patterns between RAD and FIS agreed better for fish above than below the legal minimum length (LML). All methods caught fish from a wide length-range, but the FIS caught smaller fish than the RAD. Higher catch rates for the FIS than the RAD for fish ≥ LML are explained by higher ‘encounterability’, whereas higher catch rates for fish < LML are explained by higher ‘encounterability’ and much higher ‘selectivity’ of the fishing gear. The FIS (demersal trawl, beach seine & electrofishing) methods provide reasonably unbiased indices of relative abundance and length-frequency distribution. Conversely, other than fish too small to catch during the trials, the RAD and FIS (gillnet) methods cannot be applied to indicate length class or cohort strength in the population without adjustment for the effects of species-specific selectivity.

KEYWORDS:

• Research-angler
• fishery-independent survey
• catchability
• estuary perch
• black
• bream
• Murray cod

Acknowledgments

Volunteer anglers are thanked for fishing according to agreed protocols: Trevor Beach, Chris Buxton, Jason Deenen, John Fry, Colin Hannah, Terry Johnson, Brian Kriss, Graham Lessing, Ian Lewis, Mike Linsell, Peter McDiarmid, Bob McNeill, Noel OʹConnor, Paul OʹConnor, Robert Pratt, Allan Rogers, Barry Smith, Peter Spehr, Trenton Tobias, and David Walsh. Taylor Hunt and Dr Leanne Gunthorpe of Fisheries Victoria, Dr Fabian Trinnie Department of Fisheries, Primary Industries and Regional Development, Western Australia, and Dr Vincent Vercase of Deakin University are thanked for their suggestions on early drafts of the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This study was co-funded by the Australian Government through the Fisheries Research and Development Corporation (FRDC) project 2008/005, and the Victorian Government using Recreational Fishing Licence revenue.