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Use of surveys and agent based modelling to assess the management implications of the behaviours of specialised recreational boat fishers

Tink, Calais (2015) Use of surveys and agent based modelling to assess the management implications of the behaviours of specialised recreational boat fishers. PhD thesis, Murdoch University.

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This PhD study employed two fisheries surveys and an agent-based model to characterise, in the context of specialisation theory, the behaviours and motivations of non-avid and avid fishers among a diverse group of recreational boat fishers. Broadly, specialisation theory, which relates to the field of human dimensions research, dictates that groups of recreational fishers fit along a continuum of behaviour or ‘specialisation’, from occasional, novice fishers to avid and highlyexperienced fishing specialists. Furthermore, this theory considers that fishers may be characterised according to such attributes as frequency of participation, species targeted, fishing locations and fishing gears, motivations for going fishing, preferences for resource management, as well as various other attributes.

In one survey, a sample of recreational fishers living near Perth, in Western Australia, was randomly-selected from a database containing details of recreational fishing boat licence holders in that state. Selected anglers were interviewed by phone using the Computer Assisted Telephone Interviewing (CATI) technique. Fishers were chracterised as either non-avid or avid, based on levels of participation rates, an approach consistent with many fisheries surveys. The phone survey demonstrated that Perth boat fishers are typically male, often 45-59 y and mainly target inshore, easy-to-catch ‘bread and butter’ species, such as whiting species and Australian herring. Anglers typically use rod and lines for fishing and often revisit areas in which they have experienced previous fishing success. Ownership of Global Positioning Satellite (GPS) systems was high among all surveyed boat fishers. However, compared with non-avid fishers, avid fishers were, as hypothesised according to specialisation theory, more likely to use these devices for storing fishing locations (and also for storing a greater number of locations compared to non-avid fishers). Moreover, as hypothesised, avid fishers were more likely than non-avid fishers to go fishing on a normal weekday rather than on a weekend or public holiday, presumably to avoid periods of congestion at boat ramps.

Unlike most fisheries surveys, those undertaken for this study asked a range of questions relating to movements of boat fishers when fishing. Surveyed fishers generally travelled small distances offshore (< 5 km), visited few fishing locations (≤ 4), and typically moved ≤ 3 km between their first and second fishing location, usually moving because they were not catching any fish. The hypothesis that avid fishers would be more likely than non-avid fishers to move more frequently between fishing locations when catch rates were low was not supported by the available data, however, as the durations of fishing trips were relatively short (~3.5 h) and fishers only moved a few times during each trip. It was able to be shown, however, that avid fishers are more likely to move when they receive a low fish ‘bite rate’.

A second survey, in the form of a written questionnaire, was developed to obtain data with which to characterise fishers who are members of angling clubs located in the same region as the fishers interviewed by the above phone survey. Comparisons were made between the data from the two surveys to test the hypothesis that the club members are more avid and specialised than the general population of boat fishers interviewed in the phone survey.

The surveyed club members were predominantly male, between the age of 45-59 y and almost all had more than 10 y fishing experience. These fishers were more likely than the fishers interviewed in the phone survey to own their own boat and GPS, and generally targeted a ‘mix’ of demersal reef fish species including West Australian dhufish, Glaucosoma hebraicum, and pink snapper, Chrysophrys auratus. As hypothesised, compared with non-members, club members were more avid, tended to travel further to fishing locations, typically fished in deeper waters, made greater investments in fishing technology and greater use of this (more fishing locations stored in their GPS systems), and moved more frequently between fishing locations when not receiving good fish bite rates. These findings were thus consistent with the hypothesis that club members are more specialised than avid, non-club affiliated fishers.

In the next phase of the project, an agent-based model (ABM) was employed to simulate the dynamics of the multi-species demersal, boat-based recreational fishery near Perth, in Western Australia. The model considered three fish species, West Australian dhufish and pink snapper, and a non-target species (with biological characteristics based on those of silver trevally, Pseudocaranx georgianus), and a ‘fleet’ of avid, recreational boat fishers, with characteristics similar to those of the fishers surveyed at angling clubs. The model simulated the fishing activities of this group of boat anglers in a reef fishing area (i.e. an artificial computer landscape) and subject to an established fisheries management regime (size and boat limits), and tracked their catches (released and retained) and impacts of these on fish populations. The characteristics of the individual fishers, individual fish and certain characteristics of the computer landscape were informed by a combination of biological information from existing literature and results obtained from the survey of angling club members.

Several hypotheses were explored in simulations. For example, it was demonstrated that, in simulations, fishers are able to maintain similar catch rates despite declining abundances of fish by moving more rapidly between fishing locations and by finding new locations with relatively high fish abundances. This ability of fishers to maintain catch rates was also linked to fishers updating their ‘knowledge’ of the quality of their fishing locations (i.e. as stored in a GPS) based on previous fishing experiences. Thus, it was concluded that, for this recreational demersal fishery, such ‘learning’ behaviours of fishers, and particularly their ability to improve their knowledge of good fishing locations, are key to making them highly specialised, successful fishers. It was also demonstrated that the behaviours of fishers, in response to a change in abundance of one species, can impact on the abundances of another fish species, which thus has implications for managing multi-species fisheries.

Model simulations provided a range of other results across different scenarios of initial abundance of G. hebraicum and different management regulations, some of which were not expected (i.e. not immediately intuitive), which thereby provided some useful insights regarding the dynamics of the system. For example, as initial fish abundance increased, catch per hour fishing did not always increase, a result that was attributed to management regulations limiting the number of fish that anglers may retain, reduced movements by anglers from fishing locations and reduced time spent searching by anglers. The study results also suggested that catch per unit of ‘time spent searching’ by anglers could be a useful indicator of stock abundance. The ability of anglers to maintain their catches when fish abundances were declining, through searching for new fishing locations and moving between locations more often, highlights the fact that catch rate data, as typically obtained in many surveys, do not necessarily provide a reliable index of fish abundance.

Unlike many studies relating to human dimensions research, this study focussed on understanding the key characteristics and behaviours of avid and specialised boat-based anglers in a multi-species fishery. In such an environment, different anglers are likely to adjust their behaviours in different ways to balance their fishing skills and the values they place on the mixture of species that they are likely to catch. That is, in a multi-species fishery, anglers act in a ‘multiple objective decision making framework’, and individuals respond to their own motivations and assessments of the values that they accord to the fishing experience. Although it is unlikely that the knowledge gained in one fishery will be totally applicable to the next, research methods are, however, likely to be transferable among fisheries. In this context, this study benefited from the integration of fishery surveys and simulation modelling, and consideration of the combined results in the context of specialisation theory.

Publication Type: Thesis (PhD)
Murdoch Affiliation: School of Veterinary and Life Sciences
Supervisor: Hall, Norman and Hesp, Alex
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