Andrew J. Paul

Canada's Recreational Fisheries: The Invisible Collapse?

Abstract Fishing for recreation is a popular activity in many parts of the world and this activity has led to the development of a sector of substantial social and economic value worldwide. The maintenance of this sector depends on the ability of aquatic ecosystems to provide fishery harvest. We are currently witnessing the collapse of many commercial marine fisheries due to over-exploitation. Recreational fisheries are typically viewed as different from commercial fisheries in that they are self-sustaining and not controlled by the social and economic forces of the open market that have driven many commercial fisheries to collapse. Here we reject the view that recreational and commercial fisheries are inherently different and demonstrate several mechanisms that can lead to the collapse of recreational fisheries. Data from four high profile Canadian recreational fisheries show dramatic declines over the last several decades yet these declines have gone largely unnoticed by fishery scientists, managers, an...

Instream flow needs in streams and rivers: the importance of understanding ecological dynamics

Resource managers have traditionally had to rely on simple hydrological and habitat-association methods to predict how changes in river flow regimes will affect the viability of instream populations and communities. Yet these systems are characterized by dynamic feedbacks among system components, a high degree of spatial and temporal variability, and connectivity between habitats, none of which can be adequately captured in the commonly employed management methods. We argue that process-oriented ecological models, which consider dynamics across scales and levels of biological organization, are better suited to guide flow regime management. We review how ecological dynamics in streams and rivers are shaped by a combination of the flow regime and internal feedbacks, and proceed to describe ecological modeling tools that have the potential to characterize such dynamics. We conclude with a suggested research agenda to facilitate the inclusion of ecological dynamics into instream flow needs assessments.

Spatial Distribution of Native and Nonnative Salmonids in Streams of the Eastern Slopes of the Canadian Rocky Mountains

Abstract We surveyed 53 stream reaches from the eastern slopes of the Canadian Rocky Mountains and examined the distribution of native and nonnative salmonids as related to habitat variables measured at the reach scale (100 m). The most common fishes encountered in these surveys were cutthroat trout Oncorhynchus clarki, bull trout Salvelinus confluentus, brook trout S. fontinalis, and rainbow trout O. mykiss. Of these salmonids, only cutthroat and bull trout are native to Kananaskis Country; however, cutthroat trout have also been extensively stocked throughout the region. Reach elevation, which strongly influenced mean summer stream temperatures, was the only habitat variable that was significantly related to the presence of all four salmonids. Both cutthroat and bull trout were more likely to occur in the higher elevations, whereas brook and rainbow trout were more likely to occur in the lower elevations. Because the distribution of stocked fishes is not independent of their original stocking locations,...

Assessment of alternative harvest regulations for sustaining recreational fisheries: model development and application to bull trout.

Abstract Regulations designed to protect recreational fisheries from overexploitation can fail. Regulations such as size and bag limits restrict harvest by individual anglers but not angler effort and therefore not total harvest. Even when individual harvest limits are set to zero (i.e., catch and release), a combination of hooking mortality and noncompliance may lead to fishing mortality rates that are not sustainable if angling effort is sufficiently high. These assertions were tested and quantified by using simulation experiments on a size- and age-structured model developed for a fishery on an adfluvial bull trout population. The functions and rates describing the biology and fishery were derived from a variety of sources, including published and unpublished information on bull trout and, where such sources were unavailable, from other salmonid species. The model predicts that a 40-cm minimum size limit for harvest would maintain viable populations at an annual effort up to 4 angler-hours · ha−1 · yea...

Effects of Pulsed and Continuous DC Electrofishing on Juvenile Rainbow Trout

Abstract Three hundred fifty juvenile rainbow trout Oncorhynchus mykiss, reared under captive conditions, were exposed to 300-V continuous DC or low-frequency (30-Hz) pulsed DC (PDC) for one or three electroshocking passes to evaluate the effects of electroshock on mortality, injury, and growth over 147 d. Mortality was negligible (∼1%) in all treatments. Injury rates varied from 15% to 39%, with PDC causing a greater number (but typically less severe) injuries than analogous DC sampling. Multiple-pass sampling designs caused more spinal injuries than single-pass designs. Longer (heavier) fish sustained more spinal injuries. Electroshocking reduced mean growth rates, but there were no statistically significant differences in growth between treatment groups. Growth in length was significantly reduced with increasing severity of injuries. Thus, it appears that growth was not directly impaired by electroshocking but rather by the occurrence of spinal injury, the severity of which was directly proportional to...

Can Anglers Influence the Abundance of Native and Nonnative Salmonids in a Stream from the Canadian Rocky Mountains

Abstract The proliferation of nonnative fishes throughout North America is a major concern for fisheries managers. In this paper, we evaluate the efficacy of selective harvest in reducing nonnative brook trout Salvelinus fontinalis and restoring native cutthroat trout Oncorhynchus clarki and bull trout S. confluentus populations in a small stream in the Canadian Rocky Mountains. From 1998 through 2000, groups of anglers have been involved in an organized program to selectively harvest brook trout from Quirk Creek, Alberta. Annual population estimates conducted by electrofishing indicate that selective harvest has had little effect on the brook trout population. Bayesian estimates of species catchability (i.e., proportion of vulnerable population caught per unit of angling effort) differed significantly between native and nonnative species, the catchability of native species being 2.5-fold greater than that for nonnatives. Using population models, we show that the lower catchability of brook trout coupled ...

Fish Entrainment into Irrigation Canals: An Analytical Approach and Application to the Bow River, Alberta, Canada

Abstract The Carseland Canal on the Bow River, Alberta, diverted water at a rate of 1.4–37.7 m3/s during the 2003 irrigation season. We estimated daily entrainment rates of rainbow trout Oncorhynchus mykiss, brown trout Salmo trutta, and mountain whitefish Prosopium williamsoni throughout the diversion season using population assessments of fish in the Bow River and the irrigation canal coupled to an estimate of the evacuation rate of intentionally entrained fish. Total entrainment during the irrigation season was estimated at 3,996 rainbow trout, 664 brown trout, and 2,352 mountain whitefish. Large fish (>150 mm fork length [FL]) made up 42.0% of the total number of entrained rainbow trout, 17.0% of entrained brown trout, and 0.5% of entrained mountain whitefish, representing 1.1, 0.8, and 0.3% of the total mortality observed in these Bow River populations. Earlier estimates of canal losses based on fall rescues of fish suggest that entrainment varies annually and that the 2003 estimates were low for rai...

Lateral and Longitudinal Displacement of Stream-Rearing Juvenile Bull Trout in Response to Upstream Migration of Spawning Adults

Abstract Ontogenetic shifts in fish habitat use often occur to reduce the risk of predation or cannibalism. We examined the large- and small-scale spatial behavior of juvenile Bull Trout Salvelinus confluentus during the spawning migration of adfluvial adult Bull Trout into a tributary (Smith-Dorrien Creek, Alberta) where juveniles rear. We evaluated whether juvenile spatial behavior suggested a direct response to adults that may be interpreted as an attempt to reduce predation risk. Our results showed that the juvenile response to the influx of adults was size dependent, with larger juveniles migrating downstream into Lower Kananaskis Lake and smaller juveniles moving into shallower reaches and margins of the creek. From 1992 to 2002, the downstream migration of juveniles occurred after the upstream migration of spawning adults. Juveniles migrating downstream into the lake were predominantly age 3, with some age-2 individuals. The lateral movement of juvenile Bull Trout in the creek in response to the pr...