Preliminary Assessment of the Lake Eucumbene summer recreational fishery 2015/16

Introduction: Fishery independent surveys are used to quantify recreational fisheries and support the development and evaluation of fishery management strategies around the world. Lake Eucumbene is the largest impoundment in the Snowy Mountains region of New South Wales, and contains the principal fishery for rainbow trout, Oncorhynchus mykiss, and brown trout, Salmo trutta in south-eastern Australia. A state-wide survey identified a 25% decline in catch-rates of trout (all species) from data collected in 2000/01, to comparable information collected in 2013/14. The state-wide reduction in catch-rates has contributed to increasing angler and community dissatisfaction, particularly in the Snowy Mountains region. Objectives: No standardized fishery-dependent survey data are available to quantify the recreational trout fishery in Lake Eucumbene (for metrics including effort, catch, species composition, length frequency distribution, and percentage of stocked fish) and evaluate the success of the existing management strategies. Therefore, the objectives of the current study were to; (1) quantify boat- and shore-based fishing effort, harvest and release (and their rates) within Lake Eucumbene; (2) collect information from fishers regarding targeting preferences, fishing methods, and release habits; and (3) use these data to discuss the effectiveness of current harvest restrictions and stocking strategies. Methods: Angler surveys were used to assess the recreational fishery in Lake Eucumbene during the peak fishing season (31 October 2015 to 31 January 2016). Boat- and shore-based fishing effort were quantified using progressive counts. Catch-, harvest- and release-rate information was collected from shore-based fishers using roving surveys, and from boat-based fishers using access point surveys. Resource limitations restricted boat- and shore-based surveys to 34% of Lake Eucumbene’s available surface area. Major outcomes: The shore-based fishery harvested greater numbers of, and significantly larger, rainbow and brown trout, and attracted twice the fishing effort to that of the boat-based fishery. More rainbow trout were harvested or discarded than brown trout. The catch-rate of rainbow trout (0.12 fish/fisher hr boat-based; 0.15 fish/fisher hr shore-based) was significantly higher than that of brown trout (0.08 fish/fisher hr boat-based; 0.05 fish/fisher hr shore-based) in both fisheries. Size and bag limits were largely ineffectual as anglers voluntarily released most harvest-eligible fish. In this regard, almost all released brown trout (94% boat-based; 73% shore-based) and rainbow trout (96% boat-based; 92% shore-based) were done so voluntarily as they were larger than the existing 250 mm minimum legal size. Conversely, few fish were released because they were undersized. Releasing fish because of bag limit restrictions was very rare (<0.1%). Over 83% of rainbow trout caught by anglers (i.e. the total harvested plus those released) originated from natural recruitment, rather than stocking. Almost all fishers were non-specifically targeting ‘trout’. Most anglers in the boat-based fishery used lures (73%), while bait (53%) or fly (29%), were the most common methods in the shore-based fishery. Implications for management: Because of its higher catch-ability, rainbow trout are more suitable for stocking to support the recreational fishery in the short-term during periods of recruitment failure. Catch-rates for both species in the current study appeared considerably lower than catch-rates recorded during tournaments in 2000-2004 (Faragher et al. 2007). This may imply a decline in stocks, however, care has to be taken with this interpretation as survey designs of both studies were markedly different. In particular, a probability-based sampling design was not used in 2000-2004 (which potentially introduces sampling bias), and zero catches were not included, which artificially inflated the historic catch-rates. Well designed, standardized surveys using fishery dependant (e.g. angler surveys) and independent (e.g. electrofishing, trapping) methods are required to assess change and status of trout stocks in Lake Eucumbene. The current survey provides a solid base line to evaluate change in the main characteristics of the recreational trout fishery in Lake Eucumbene. To ensure sustainability of the recreational fishery in NSW inland waters, the development of harvest strategies including simple and robust ecological, economic and/or social objectives, performance indicators and reference points for trout and other recreational freshwater species (e.g. Murray cod, silver perch and golden perch, Australian bass) is of utmost importance. The need for an appropriate harvest strategy for trout in Lake Eucumbene is illustrated by the high prevalence of voluntarily released legal sized fish that caused existing output controls (size and bag limits) to be largely ineffectual as management tools to control fishing mortality