Discussion and Conclusions
Statewide Angler Diary Program 1997 - 2003
An important aspect of modern fishery management is stakeholder involvement in the assessment process. This report demonstrates how experienced anglers can assist in the assessment of a range of Victorian recreational fisheries by providing catch information through a structured program. Sampling strategies and data analysis approaches used in this study aimed to provide a time series of angler catch information that would reflect trends in the abundance and size composition of fish stocks. Generally, recreational fisheries surveys collect catch data for the purposes of estimating the retained catch, which involves surveying a representative sample from recreational angler catches. Representative recreational catch samples include catches from less skilled anglers, whose catches may not provide a good indication of stock abundance. The benefit of recruiting the more skilled and motivated anglers into the Angler Fishing Diary Program is that catches reported are more likely to reflect fish stock abundance, and do so with greater accuracy and precision. Analysing reported catch rates by target species also allowed the exclusion of catch data from fishing trips that were principally directed at species other than the species of interest. This approach may result in more accurate and precise indication of the stock abundance, particularly when estimates are based on catch data from anglers fishing in multi-species fisheries such Port Phillip Bay and Western Port.
Trends in annual catch rates and size composition from the six fisheries studied showed the potential for the Angler Fishing Diary Program to provide indicators of the status of fish stocks over an extended time period. The consistently higher catch rates of under-size snapper in Port Phillip Bay (relative to the legal-sized snapper) suggests higher abundance of young snapper from strong recent recruitment. In contrast, under-size snapper in Western Port were only reported in relative high abundance in one of five years. This difference in catch rates is interesting given that the bays are adjacent to each other and the fish are considered part of a single Western Victorian stock. The lower annual catch rates of legal-size compared to under-size snapper suggests that snapper above the LML are less abundant or less susceptible to capture by anglers than those under the LML, in both Port Phillip Bay and Western Port.
Catch rates of King George whiting initially showed a declining trend for fish over the LML in both Port Phillip Bay and Western Port. In 2002/03, however, retained catch rate increased for anglers fishing in Port Phillip Bay, but not in Western Port. Initially, this was surprising since whiting stocks within both bays are believed to be dependent on the same larval supply, via Bass Strait currents, from spawning grounds in the coastal waters off Western Victoria and beyond (Jenkins et al. 2000). However the size composition of whiting in anglers catches suggest that anglers fishing in Western Port access more larger (and presumably older) fish than those fishing in Port Phillip Bay. Such apparently stable spatial differences in the size composition of King George whiting catches potentially explains the lag between a rise in catch rates in Port Phillip Bay and Western Port.
Only a small component of King George whiting catches reported by anglers comprised fish under 25 cm FL, even in the first years of the study when under-size whiting had been observed in abundance in studies using other fishing methods (Knuckey et al. 2001). Under-size whiting appeared not be vulnerable to the fishing gear used by whiting anglers, and therefore the catch rate of under-size whiting is probably not a good indicator of likely future recruitment to the fishery.
A declining trend in black bream release rates from 1997/98 to 2001/02, followed by a decline in retained catch rates since 2000/2001 is consistent with the timing of recruitment from the last strong bream year-class to the fishery (from the 1994/95 spawning season). As with snapper, the generally lower catch rates for retained versus released bream suggests that bream above the LML are less abundant or less susceptible to capture by anglers than those under the LML. The release catch rates and catch composition reported by anglers in 2002/03 show signs of a potentially more abundant bream year-class. However, the extent to which this group of bream will impact on the fishery will only become clear in the next couple of years, as they become more susceptible to capture.
Total catch rates of both brown and rainbow trout from the Goulburn River were quite variable in two of the five years sampled, mainly because of low numbers of reported fishing trips. There was no clear trend in abundance of trout, and catch rate performance indicators would benefit from the involvement of more anglers reporting trout catches from the Goulburn river in the future.
Time series of size composition data for a species, in conjunction with data on catch rates, can be used to infer changes in fishing pressure. This may be more accurate for fisheries such as black bream or brown trout, where the species remains susceptible to fishing for a number of years, than for migratory species such as snapper and King George whiting, or for species that have a relatively short life span, such as rainbow trout. Such data for fish below the LML can also allow predictions to be made about the strength and timing of future recruitment to the fishery, if the growth rate is known.
The fishing motivation for anglers participating in the Program in 2002/03 fell into distinct groups: non-catch related motives such as relaxing and being outdoors, and catch related motives of sport or food. Angler satisfaction levels in 2002/03 for the six case study fisheries corresponded with the catch rate and size composition of their catch. This is consistent with the catch related motives for fishing but not the non catch-related motivations. Higher angler skill levels and possibly higher expectations may ultimately influence satisfaction levels of some anglers whose primarily motive for fishing is non-catch related. The fishing motivations and satisfaction levels of the anglers that participated in the survey are unlikely to be representative of the motivations and satisfaction levels of the wider recreational fishing community.
The Angler Fishing Diary Program is an example of a cost-effective approach to providing fisheries managers with annual performance indicators for many Victorian fisheries. The use of a structured program whereby fish stock performance indicators are generated through a partnership between researchers and experienced anglers allows greater accountability and continuity in terms of the assessment advice provided to fisheries managers. However, there are limitations to this approach. For the data to be useful as a performance indicator, the skill profile and behaviour of the participating diary anglers in each fishery, or for each target species, have to be constant over time or changes must be able to be quantified. Indicators derived from such data are likely to be increasingly robust as the number of anglers increases, as it becomes less likely that the catches of a few anglers can unduly affect the results. If this assessment approach is to be continued in the future, care should taken if assessment advice is based on the reported catches from just a few anglers. As with any self-reporting catch program there is a possibility of prestige bias, the potential effect of non-reporting of nil or poor catches. Monitoring and reducing non-reporting of catches should be an important component of the Angler Fishing Diary Program in the future.
The development of the Angler Fishing Diary Program in Victoria has enable indicators of trends in the status of fish stocks to be provided by a group of highly skilled and motivated anglers. The Angler Fishing Diary Program is an example of a cost-effective approach to providing fisheries managers with fish stock assessment . advice. Plans to further expand this program should included identifying important fish stocks where an increase in the reported fishing activity by diary anglers will improved the accuracy of stock status indicators.
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