Search

This study evaluated the status of native and stocked fish species in 13 prairie lakes in central Canada over eight years (2007–14) using three metrics: resource‐use (benthic versus pelagic carbon via stable isotopes); body condition (relative weight index Wr); and parasite load (cestode gut enumerations). Analyses included game and non‐game fishes, like naturally occurring northern pike, Esox lucius L., and yellow perch, Perca flavescens Mitchill, but focused on stocked walleye, Sander vitreus (Mitchill) because it supports a robust recreational fishery. Walleye and northern pike were significantly more reliant on benthic carbon than yellow perch or forage fishes (p < 0.05), but this reliance was not associated with any measured environmental variables for any species. In lakes with game fishes, forage fishes exhibited higher reliance on benthic energy, possibly due to predator avoidance strategy, particularly yellow perch. Walleye body condition index was consistently lower (<95–105) than values exhibited by the other two game fishes (81–139), and parasites were only common in walleye and associated with lake‐water salinity (r2 = 0.93, p < 0.05) and sex (p < 0.05). Based on the results, the most desirable game fish, walleye, appears less resilient to environmental variability than northern pike and yellow perch, making this species more susceptible to impacts of future climate change. [ABSTRACT FROM AUTHOR]

We investigated the effects of circle hook size and angling technique on hooking location, capture success, and postrelease mortality in salmonids by using hatchery-reared Rainbow TroutOncorhynchus mykiss. Fish were caught using a range of inline circle hook sizes (4, 6, 8, and 10) baited and fished both actively and passively. While hook size had no influence on capture rates, active fishing resulted in significantly higher capture rates. Very few mortalities (2%) were observed across angling methods or hook sizes during 72 h of postrelease monitoring. However, significantly more fish were deeply hooked with passive fishing. Contrary to claims by manufacturers and sportfishing entities, mounting evidence indicates that passively fished circle hooks have lower capture rates and might actually increase deep hooking in salmonids. Received May 19, 2015; accepted November 12, 2015 Published online March 21, 2016 [ABSTRACT FROM AUTHOR]

We compared the effectiveness of baited circle hooks and J hooks in catch-and-release angling for wild, stream-dwelling Brook TroutSalvelinus fontinalis. We caught 201 Brook Trout using active and passive techniques to assess the influence of hook type and angling method on capture efficiency, hooking location, handling time, deep-hooking rates, and postrelease mortality (up to 48 h). Anglers recorded an average catch rate of 7.6 trout/h over 26.25 total hours of fishing. Actively fishing with J hooks was the most effective at landing Brook Trout (82.3%). Only 10% (n= 20) of all fish were deeply hooked, and half of those were caught when anglers were passively fishing with J hooks. Larger fish were significantly more likely to be deeply hooked. However, no fish were deeply hooked when anglers passively fished with circle hooks. The most common hooking location among treatments was the corner of the mouth (40%,n= 80). Eye injuries due to hooking were relatively uncommon (6.5%) and occurred less frequently than deep hooking. Overall mortality rates were very low (2%,n= 4) and were probably influenced by low deep-hooking rates in concert with cool water temperatures and experienced anglers equipped with the necessary tools to efficiently release the trout. Received May 19, 2015; accepted November 12, 2015 Published online March 16, 2016 [ABSTRACT FROM AUTHOR]

The anticipated impacts of climate change on aquatic biota are difficult to evaluate because of potentially contrasting effects of temperature and hydrology on lake ecosystems, particularly those closed-basin lakes within semiarid regions. To address this shortfall, we quantified decade-scale changes in chemical and biological properties of 20 endorheic lakes in central North America in response to a pronounced transition from a drought to a pluvial period during the early 21st century. Lakes exhibited marked temporal changes in chemical characteristics and formed two discrete clusters corresponding to periods of substantially different effective moisture (as Palmer Drought Severity Index, PDSI). Discriminant function analysis ( DFA) explained 90% of variability in fish assemblage composition and showed that fish communities were predicted best by environmental conditions during the arid interval ( PDSI <−2). DFA also predicted that lakes could support more fish species during pluvial periods, but their occurrences may be limited by periodic stress due to recurrent droughts and physical barriers to colonization. Zooplankton taxonomic assemblages in fishless lakes were resilient to short-term changes in meteorological conditions, and did not vary between drought and deluge periods. Conversely, zooplankton taxa in fish-populated lakes decreased substantially in biomass during the wet interval, likely due to increased zooplanktivory by fish. The powerful effects of such climatic variability on hydrology and the strong subsequent links to water chemistry and biota indicate that future changes in global climate could result in significant restructuring of aquatic communities. Together these findings suggest that semiarid lakes undergoing temporary climate shifts provide a useful model system for anticipating the effects of global climate change on lake food webs. [ABSTRACT FROM AUTHOR]

We surveyed large wood volumes in relation to the distribution and density of rainbow trout Oncorhynchus mykiss and steelhead (anadromous rainbow trout) in 15 stream reaches in the upper Salinas River watershed, California, which represents the southern end of the species’ range. The main tree species contributing to large wood were hardwoods: coast live oak Quercus agrifolia, California sycamore Platanus racemosa, red willow Salix laevigata, and valley oak Q. lobata. Large wood jams were important in pool formation and typically had red willow as their key pieces. Temperatures were exceptionally warm during the study period. No steelhead were observed at sites where the mean water temperature exceeded 21.5°C or the maximum water temperature exceeded 26°C. The combined importance of high temperatures and large wood on the distribution and abundance of southern steelhead indicates that suitable habitat may be reduced if climate change continues on its present course of warming and the frequency of fires increases. Received February 9, 2011; accepted July 18, 2011 [ABSTRACT FROM PUBLISHER]

Endorheic lakes of the northern Great Plains encompass a wide range of environmental parameters (e.g., salinity, pH, DOC, Ca, nutrients, depth) that vary 1000-fold among sites and through the past 2000 years due to variation in basin hydrology and evaporative forcing. However, while many environmental parameters are known to individually influence zooplankton diversity and taxonomic composition, relatively little is known of the hierarchical relationships among potential controls or of how regulatory mechanisms may change in response to climate variation on diverse scales. To address these issues, we surveyed 70 lakes within a 100 000 km prairie region to simulate the magnitude of environmental change expected to occur over 100-1000 years and to quantify the unique and interactive effects of diverse environmental parameters in regulating pelagic invertebrate community structure at that scale. Multivariate analyses showed that salinity was the principal correlate of changes in invertebrate composition among lakes, with a sequential loss of taxa between salinities of 4 and 50 g total dissolved solids L until one to two species predominated in highly saline systems. In contrast, changes in the concentrations of Ca and other mineral nutrients exerted secondary controls of invertebrate assemblages independent of salinity, whereas lake depth provided a tertiary regulatory mechanism structuring species composition. In contrast to these large-scale hierarchical patterns, seasonal surveys (May, July, September) of a subset of 21 lakes in each of 2003-2005 revealed that annual meteorological variation had no measurable effect on pelagic invertebrates, despite large differences in temperature, precipitation, and evaporation arising from regional droughts. Together these findings show that pelagic invertebrate communities in saline lakes are resilient to interannual variability in climate, but suggest that lakes of the northern Great Plains may provide a sensitive model to forecast centennial effects of future climate change. [ABSTRACT FROM AUTHOR]