Use of binary and truncated regression models in the analysis of recreational fish catches

Estuaries provide one of the most popular areas for commercial and recreational anglers to fish. At present, no estuary-specific study of recreational fisheries resources has been attempted in southern Queensland, Australia. The work reported in this thesis provides a detailed analysis on the recreational catch of the yellowfin bream (Acanthopagrus australis), dusky flathead (Platycephalus fuscus) and sand whiting {Sillago ciliatd) resources in the Burnett River, Maroochy River and Pvmiicestone Passage. Recreational fishing data typically contain a large proportion of zero values and show variability or dispersion greater than that allowed for in many standard regression models (eg Normal and Poisson) and the assumptions required for these analyses will not be valid. In this thesis a two stage regression approach involving a binary (non-zero/zero catch) response and the non-zero catches was used for analysing recreational fish catches to accoimt for the extra zeros and over-dispersion present in the data. Also, the statistical bootstrap method was utilised to estimate confidence intervals on total recreational catch given the large proportion of zero catches. Unlike the Queensland commercial fisheries, which provide catch returns, the recreational catch was unknown and needed to be estimated. Recreational catch and fishing effort data from roving creel surveys were collected between June 1997 and August 1998. This method involved a person on the water counting and interviewing boat and shore fishers at a variety of locations and times. The number of people fishing and the resulting harvest differed between estuaries. More people fished during winter than at any other time of the year. Annual recreational fishing effort was of the order of 13 000 angler visits to the Burnett River, 28 000 to the Maroochy