Estimating the marine recreational fishing catch 25 November 2002
Estimating the marine recreational fishing catch might at first glance seem to be a relatively easy thing to do. It is certainly a very important piece of information which, along with commercial catch data, is vitally important for the management of our fisheries. Estimates are required of the recreational catch for each fish stock. This is particularly important for highly valued recreational species such as snapper, blue cod, kahawai, kingfish, paua and rock lobster. Most of these species also have a high commercial value. However determining the recreational catch can be difficult. Commercial fisheries are required to report their landings so that information on the commercial catch is easily obtainable, and with a very high degree of accuracy.
The first estimates of marine recreational fishing catch were made in a series of recreational surveys conducted over the summers 1991/92, 1992/93 and 1993/94. The first truly national survey, a survey of the whole country at once, was undertaken in 1995/96. This was followed with a second national survey in 1999/2000. These surveys are undertaken by independent researchers under contract to MFish. Recreational research is planned, discussed and reviewed through the Recreational Research Planning Group convened by MFish. All stakeholders; commercial, recreational, customary and environmental representatives, participate in this research planning process.
The two national surveys have been done by what is known as the telephone/diary survey. Households are contacted by telephone and fishers are asked if they will keep a diary recording their fishing activity over a whole year. In addition, surveys at boat ramps around the country are used to obtain data on the size and weight of individual species caught by recreational fishers. With the diaries and the boat ramp information, an estimate of the numbers and weight of fish taken by diarists can be accurately determined. However the difficulty arises when the estimate from the diary participants has to be extended to the whole of the population who went fishing. Obviously not everyone who goes fishing keeps a diary. The logistics of every fisher keeping a diary for the purposes of estimating recreational catch is not feasible. To multiply up the diarist data, the proportion of people in the population who go fishing, a formula is used. This formula, referred to as "prevalence estimate" provides the main difficulty.
The two national surveys have produced, in some cases, vastly different estimates of the recreational catch of some species in different areas. The overall increase is approximately 300%. To try and reconcile the differences between the two surveys, MFish commissioned and independent review of the results of the two surveys. The main conclusion from this review was that major factor influencing the accuracy and reliability of the two surveys was the estimate of fisher prevalence. The first survey in 1995/96 used a prevalence estimate of 13.9% while the second survey gave several prevalence estimates, varying from 29 to 51%, depending on the method used. MFish is still reviewing the research report from the 199/2000 survey, and the report has not yet been formally accepted. However discussion of the draft results at a meeting of the research planning group held in September, and the independent review of the estimates from the two surveys, demonstrates that confidence in the catch estimates is compromised by the variable estimates of fisher prevalence.
A new national survey is planned for 2004/2005. Before this is undertaken MFish will be holding a workshop in March 2003 to discuss the design of the new survey. Although surveys of recreational fishing in freshwaters have been undertaken in many countries over many years, surveys of country wide marine recreational fisheries are not so common. The important difference with the freshwater surveys is that there is usually some sort of registration or licensing system in place to identify how many people go fishing. A national survey has recently been undertaken in Australia. This survey has benefited from the two surveys in New Zealand and the lessons learnt. In turn the next survey in New Zealand will build on the results of the two previous surveys and the more recent Australian study.
For further information please contact
Peter Todd, Ministry of Fisheries Science Policy
Tel 03 548 1069