Diet overlap of non‐native alewife with native yellow perch and spottail shiner in nearshore waters of southwestern Lake Michigan, 2000–2007

Abstract – Lake Michigan has experienced many ecological changes as a result of introductions of non‐native species. Arguably the most significant was that of alewife (Alosa pseudoharengus), yet studies on diet overlap with native species are lacking. We analysed diet trends of alewife, spottail shiner (Notropis hudsonius) and yellow perch (Perca flavescens) collected in summer and fall 2000–2007 near Waukegan, IL, in 3–10 m depths. Mean percentage composition by dry weight for 23 prey taxa was used in multivariate analysis to test whether diet differed across species and size classes. We also tested whether zooplankton and benthic invertebrate community composition changed over time. Fish diets were similar over all years but differed seasonally. In summer, diets of large alewife were similar to both small alewife and small yellow perch, with Bosminidae, chironomid larvae and copepods as primary common prey. During fall, alewife and yellow perch size classes exhibited strong intraspecific diet overlap, while there was low diet overlap between species. Primary distinctions between species’ diets in fall were higher consumption of amphipods by yellow perch and dreissenids by spottail shiners compared to alewife, which consumed higher proportions of zooplankton. Overall, high yellow perch diet overlap with alewife during summer and with their larger conspecifics during fall could lead to negative implications for yellow perch growth before the critical overwintering period. Detailed insights into diet overlap and prey availability are critical first steps in understanding competitive interactions between native and non‐native fish that dominate the nearshore community in southwestern Lake Michigan.     

Factors influencing the abundance of three common nearshore fishes in south‐west Lake Michigan

Variation in the distribution and abundance of nearshore fishes is critical to understand food web processes and fishery management issues in Lake Michigan. This study characterised patterns in abundance of three common nearshore species, yellow perch Perca flavescens (Mitchell), round goby Neogobius melanostomus (Pallas) and alewife Alosa pseudoharengus (Wilson), in relation to spatio‐temporal, abiotic and biotic factors using gillnet sampling conducted across 5 years at multiple locations representing different substrates. Significant variations were observed in alewife and round goby catches between locations. A negative relationship between round goby and age‐0 yellow perch catch was observed, indicating potential competition between the two species. This study demonstrates that variability in nearshore fish communities can be driven by factors including substrate and interspecific interactions. Given the prominent role these species play in Lake Michigan's food web and thus their importance to fishery production, a thorough understanding of these factors is warranted.     

Declines in the energy content of yearling non‐native alewife associated with lower food web changes in Lake Michigan

Juveniles of non‐native alewife, Alosa pseudoharengus (Wilson), were collected in Lake Michigan in 1998, 1999, 2010, 2011 and 2013 to evaluate changes in energy content during a period of major ecosystem changes. Consistent with historical data, energy content of yearling alewife declined from late winter into late spring and was at its lowest point in June. Energy density and length‐adjusted, entire‐body energy were lower in 2010, 2011 and 2013 than in 1998 and 1999. Energy losses over the first winter in the lake were more severe for the 2010 year class (56% decrease) than for the 1998 year class (28% decrease). Alewife diets in late spring of 2010–2013 reflected the loss of major prey such as Diporeia spp. and a shift towards lower energy prey. The recent decline in energy content of yearling alewife can be linked to recent changes in productivity and abundance of key components of the lower food web of Lake Michigan following the dreissenid invasion.     

Factors influencing recruitment and growth of age‐0 yellow perch in eastern South Dakota glacial lakes

Variation in recruitment and growth of age‐0 yellow perch, Perca flavescens (Mitchill), was modelled across a range of nine eastern South Dakota glacial lakes to: (i) estimate factors influencing recruitment and growth dynamics during early ontogeny; and (ii) determine the relative importance of biotic versus abiotic processes in regulating recruitment and growth dynamics. Results provide a framework for future investigations and suggest that abiotic factors were more important in regulating recruitment of age‐0 yellow perch, whereas biotic factors were more important in regulating growth. Recruitment was positively related to springtime water levels and temperature and negatively related to spawning stock biomass and springtime wind conditions. By contrast, growth was negatively related to abundance of conspecifics and potential competitors (i.e. bluegill, Lepomis macrochirus Rafinesque) and positively related to abundance of potential predators [i.e. walleye, Sander vitreus (Mitchill) and northern pike, Esox lucius Linnaeus].     

The influence of abiotic factors on gillnet catch rates of yellow perch in southern Lake Michigan, 1989–2006

Abstract The difference in yellow perch, Perca flavescens (Mitchill), catch rates were evaluated for gillnets set on the bottom at 10‐ and 15‐m depths in southern Lake Michigan during June, July and August from 1989 to 2006. More yellow perch were captured in gillnets set at 10 m than at 15 m. Differences in water temperature were significant in explaining variation in catch rates, but differences in Secchi depth and wave height were not significant. These results suggest that yellow perch may associate with habitat based on water temperature during the summer and move in response to thermal changes. In addition, this portion of the lake lacks noticeable heterogeneous structural habitat features that normally influence yellow perch behaviour. Fisheries managers should consider sampling based on temperature in addition to depth or other habitat features when designing sampling protocols.     

Evaluating potential competitive bottlenecks between invasive common carp and native bluegill and yellow perch

Processes influencing fish recruitment are often highly complex and inherently difficult to understand. Invasive species may complicate recruitment through habitat and food web modifications resulting in competitive bottlenecks. Common carp Cyprinus carpio have been distributed worldwide, and their introductions have resulted in destructive effects on aquatic ecosystems and food web dynamics. Common carp are highly fecund, and high densities of age‐0 carp may occur in some years that may reduce invertebrate prey resources and adversely affect native age‐0 fishes. We used enclosures and field observations to examine potential effects of age‐0 common carp on growth and survival of age‐0 yellow perch Perca flavescens and bluegill Lepomis macrochirus. Yellow perch and bluegill were stocked into enclosures with and without common carp (31 fish/m³) using a substitution experimental design, and fish growth and survival and invertebrate prey resources were assessed. Common carp reduced growth of yellow perch but not bluegill and did not affect survival of either species in mesocosms. Next, we used patterns of common carp, bluegill, and yellow perch abundance and total length across 38 lake‐years to evaluate potential interspecific interactions in natural systems. Age‐0 common carp abundance was not negatively related to size or abundance of bluegill or yellow perch. However, adult common carp and age‐0 yellow perch abundance were inversely related, suggesting a potential competitive bottleneck. Thus, age‐0 common carp may suppress growth of yellow perch when prey is limited, but adult common carp may have larger effects than early life stages on native juvenile fishes.     

Recruitment of burbot (Lota lota L.) in Lake Erie: an empirical modelling approach

Stapanian MA, Witzel LD, Cook A. Recruitment of burbot (Lota lota L.) in Lake Erie: an empirical modelling approach.
Ecology of Freshwater Fish 2010: 19: 326–337. Published 2010. This article is a US Government work and is in the public domain in the USA Abstract – World‐wide, many burbot Lota lota (L.) populations have been extirpated or are otherwise in need of conservation measures. By contrast, burbot made a dramatic recovery in Lake Erie during 1993–2001 but declined during 2002–2007, due in part to a sharp decrease in recruitment. We used Akaike’s Information Criterion to evaluate 129 linear regression models that included all combinations of one to seven ecological indices as predictors of burbot recruitment. Two models were substantially supported by the data: (i) the number of days in which water temperatures were within optimal ranges for burbot spawning and development combined with biomass of yearling and older (YAO) yellow perch Perca flavescens (Mitchill); and (ii) biomass of YAO yellow perch. Warmer winter water temperatures and increases in yellow perch biomass were associated with decreases in burbot recruitment. Continued warm winter water temperatures could result in declines in burbot recruitment, particularly in the southern part of the species’ range.     

Spatial and temporal segregation of yellow perch in southern Lake Michigan

Historically, yellow perch, Perca flavescens Mitchill held great recreational and commercial importance to the Lake Michigan fishery. Unfortunately, fluctuations in lake‐wide abundances in the past four decades created inconsistencies in catch. As adults, yellow perch have been commonly observed to swim great distances suggesting there is likely to be partitioning of the population within the lake. The objective was to determine whether population demographics of yellow perch in the Indiana waters of Lake Michigan were consistent with a single population. Seasonal population demographics of yellow perch collected from the Indiana waters of Lake Michigan in 2009, 2011 and 2012 were compared. Catch‐per‐unit‐effort of female yellow perch increased during later sampling periods across years. Similarly, total length of females and males increased 10% throughout the year. The proportion of females increased from 20% at the beginning of the survey period to 95% at the end. A few larval yellow perch were collected. These data suggest that Indiana waters of Lake Michigan are not a primary spawning area, rather these waters serve as a feeding or recovery area for post‐spawned yellow perch, particularly females.     

Adapting a multi‐species tool for single‐species impact assessments: Managing fishes at risk in Canada

1. To assess the impacts of human activity on fishes and fish habitat, impact assessment tools use single‐ and multi‐species approaches depending on the ecological and socio‐economic objectives. In Canadian aquatic ecosystems, single‐ and multi‐species impact assessments are guided by the Species at Risk Act and Fisheries Act, respectively. Yet, for species protected under the Species at Risk Act, the sparse data often require alternative approaches to risk assessment.
2. The goal of this study was to evaluate whether a database‐derived multi‐species tool – the Habitat Ecosystem Assessment Tool (HEAT) – can be used for single‐species impact assessments. Using an empirical example of proposed drain maintenance in a tributary of Lake St. Clair, the net loss of suitable habitat was evaluated across six conservation targets, ranging from single species, such as the pugnose shiner (Notropis anogenus) and the yellow perch (Perca flavescens), to the entire fish assemblage. Model outcomes were compared across various habitat suitability indices, spatial resolutions, and environmental habitat layers.
3. The net loss of suitable habitat varied widely across conservation targets and was greatest for the rare specialist species (pugnose shiner). Single‐species conservation targets were more sensitive to variation in spatial resolution and uncertainty in model input parameters. The results of this study emphasize that single‐ and multi‐species conservation targets should not be considered equal, especially when species differ in abundance and niche breadth.
4. This study demonstrates the flexibility of HEAT for evaluating potential impacts of human disturbance on fishes and their habitat. Future development of this tool should expand beyond physical habitat, to include other factors relevant to species distribution and survival (e.g. biotic interactions).

     

Perch production in forest lakes: the contribution of abiotic and biotic factors

Horppila J, Olin M, Vinni M, Estlander S, Nurminen L, Rask M, Ruuhijärvi J, Lehtonen H. Perch production in forest lakes: the contribution of abiotic and biotic factors.
Ecology of Freshwater Fish 2010: 19: 257–266. © 2010 John Wiley & Sons A/S Abstract – The biomass, growth and production of perch (Perca fluviatilis (L.)) in five humic forest lakes in southern Finland were estimated and the abiotic and biotic factors contributing to the between‐lake differences were explored. The average perch biomass in the study lakes varied from 13.1 to 45.6 kg·ha^?1 and annual production from 6.0 to 16.5 kg·ha^?1. The highest biomass and production were found in Lake Majajärvi with highest water colour and nutrient concentration. Variability in fish density rather than in individual growth rate seemed to be the main factor behind the between‐lake differences in perch production. No dependence of perch production on water transparency was found, because transparency had a stronger effect on individual growth than on fish density. The length increment of perch in their second year increased significantly with water transparency but at older ages no such dependence was found. At age of 4 years, the growth rate of perch decreased with perch density, indicating intraspecific competition for benthic food resources. At age of 7 years, the growth rate increased with increasing roach (Rutilus rutilus (L.)) abundance, suggesting that roach served as a resource for piscivorous perch. The effects of predatory top‐down control on perch populations were probably obscured due to the variable size and water quality of the study lakes.     

Polyphasic characterization of Aeromonas salmonicida isolates recovered from salmonid and non‐salmonid fish

Michigan's fisheries rely primarily upon the hatchery propagation of salmonid fish for release in public waters. One limitation on the success of these efforts is the presence of bacterial pathogens, including Aeromonas salmonicida, the causative agent of furunculosis. This study was undertaken to determine the prevalence of A. salmonicida in Michigan fish, as well as to determine whether biochemical or gene sequence variability exists among Michigan isolates. A total of 2202 wild, feral and hatchery‐propagated fish from Michigan were examined for the presence of A. salmonicida. The examined fish included Chinook salmon, Oncorhynchus tshawytscha (Walbaum), coho salmon, O. kisutcha (Walbaum), steelhead trout, O. mykiss (Walbaum), Atlantic salmon, Salmo salar L., brook trout, Salvelinus fontinalis (Mitchill), and yellow perch, Perca flavescens (Mitchill). Among these, 234 fish yielded a brown pigment‐producing bacterium that was presumptively identified as A. salmonicida. Further phenotypic and phylogenetic analyses identified representative isolates as Aeromonas salmonicida subsp. salmonicida and revealed some genetic and biochemical variability. Logistic regression analyses showed that infection prevalence varied according to fish species/strain, year and gender, whereby Chinook salmon and females had the highest infection prevalence. Moreover, this pathogen was found in six fish species from eight sites, demonstrating its widespread nature within Michigan.     

Habitat use by age-0 yellow perch in two South Dakota glacial lakes

Abstract– We determined the habitat use of age-0 yellow perch ( Perca flavescens ) in two South Dakota (USA) lakes. Larval perch abundance was based on trawl catches and related to environmental variables on two late spring dates. Juvenile perch abundance was based on late July shoreline seine and bottom trawl catches. Day and night juvenile abundance relations to environmental variables were examined. Larval abundance appeared to be related to biological environmental variables, and no significant (P≥0.05) correlations with physical habitat variables were found. Juvenile yellow perch abundance was related to physical variables, particularly substrate, water temperature and water depth. The only biological variable that could be related to juvenile abundance was chironomid abundance. Finally, juvenile perch abundance was positively associated with abundance of other juvenile fishes and minnows, but these associations varied by lake, time of day and habitat type. Understanding age 0 perch habitat use will allow fishery biologists to better assess sampling designs and recruitment processes.     

Response of walleye and yellow perch to water‐level fluctuations in glacial lakes

The influence of water levels on population characteristics of yellow perch, Perca flavescens (Mitchill), and walleye, Sander vitreus (Mitchill), was evaluated across a range of glacial lakes in north‐eastern South Dakota, USA. Results showed that natural variation in water levels had an important influence on frequently measured fish population characteristics. Yellow perch abundance was significantly (P < 0.10) greater during elevated water levels. Yellow perch size structure, as indexed by the proportional size distribution of quality‐ and preferred‐length fish (PSD and PSD‐P), was significantly greater during low‐water years, as was walleye PSD. Mean relative weight of walleye increased significantly during high‐water periods. The dynamic and unpredictable nature of water‐level fluctuations in glacial lakes ultimately adds complexity to management of these systems.     

Temperature,plankton and conspecific density influence dynamics of age‐0 gizzard shad: implications for a gape‐limited piscivore

Age‐0 gizzard shad Dorosoma cepedianum are the main prey fish for white crappies Pomoxis annularis in many US reservoirs. However, these prey fish commonly outgrow their vulnerability to white crappie predation in some, but not all, northern Missouri reservoirs. Potential variables that could influence abundance, growth and mortality of age‐0 gizzard shad were examined in three reservoirs that differed with respect to age‐0 gizzard shad growth rates. Because of thermal effluent from a power plant, gizzard shad spawned earlier in Thomas Hill Lake and initial densities of larvae were greater than in the other reservoirs. Larval and juvenile gizzard shad grew slowest in Thomas Hill Lake, followed by Mark Twain Lake and Long Branch Lake. Growth rate of larvae increased with increasing water temperature and food abundance, but decreased with increasing conspecific density. Similar relationships were found for juvenile growth, except that growth declined with increasing temperature. The slower growth of larvae and juveniles in Thomas Hill Lake was probably a consequence of their greater densities relative to their food abundance and higher water temperatures during the juvenile stage. Conversely, both larvae and juvenile gizzard shad grew more rapidly and juveniles attained large sizes in Long Branch Lake owing to their lower densities relative to their available food. Mortality of larvae and juveniles was mostly similar among the reservoirs. Because of their greater abundance and slower growth, gizzard shad were available as prey for white crappies for a longer period in Thomas Hill Lake than in the other reservoirs.     

Changes in yellow perch length frequencies and sex ratios following closure of the commercial fishery and reduction in sport bag limits in southern Lake Michigan

Abstract  The closure of the Indiana commercial fishery in Lake Michigan in 1997 provided the opportunity to examine the effects of commercial exploitation on the yellow perch, Perca flavescens (Mitchill), population. Data from annual gillnet and trawl sampling, recreational angler creel surveys and commercial fishing harvest were used to determine whether changes in length–frequency distributions and sex ratios were altered following closure. The proportions of large, adult yellow perch were significantly greater after the closure of the commercial fishery. Overexploitation of fish >200 mm by commercial harvest likely truncated the size distribution, but recreational harvest was comparatively small and did not appear to be a factor influencing size distributions. This post-closure period also had a greater proportion of females in trawl catches, and the mean length of harvested fish increased in the recreational fishery. These findings suggest commercial exploitation influenced yellow perch population dynamics in far southern Lake Michigan.     

The effect of predation on stunted and nonstunted white perch

Gosch NJC, Pierce LL, Pope KL. The effect of predation on stunted and nonstunted white perch.
Ecology of Freshwater Fish 2010: 19: 401–407. © 2010 John Wiley & Sons A/S Abstract – Predation is widely regarded as a means to prevent or minimise the establishment of a stunted (high density of slow growing individuals) population. We investigated the effect of predation on two different white perch Morone americana populations (stunted and nonstunted) by examining the stomach contents of piscivorous fishes. White perch and gizzard shad dominated piscivore diets in Branched Oak Lake, whereas white perch dominated piscivore diets in Pawnee Lake. White perch consumed in the stunted population (Branched Oak Lake) were larger and older than white perch consumed in the nonstunted population (Pawnee Lake). Many of the consumed white perch in the stunted population were sexually mature and had the opportunity to spawn at least once. In contrast, all of the consumed white perch in the nonstunted population were sexually immature. Predation may have reinforced the stunting of white perch in Branched Oak Lake through removal of the largest, oldest individuals.     

Environmental factors regulating the recruitment of walleye Sander vitreus and white bass Morone chrysops in irrigation reservoirs

Understanding the environmental factors that regulate fish recruitment is essential for effective management of fisheries. Generally, first‐year survival, and therefore recruitment, is inherently less consistent in systems with high intra‐ and interannual variability. Irrigation reservoirs display sporadic patterns of annual drawdown, which can pose a substantial challenge to recruitment of fishes. We developed species‐specific models using an 18‐year data set compiled from state and federal agencies to investigate variables that regulate the recruitment of walleye Sander vitreus and white bass Morone chrysops in irrigation reservoirs in south‐west Nebraska, USA. The candidate model set for walleye included only abiotic variables (water‐level elevation, minimum daily air temperature during winter prior to hatching, annual precipitation, spring warming rate and May reservoir discharge), and the candidate model set for white bass included primarily biotic variables (catch per unit effort (CPUE) of black crappie Pomoxis nigromaculatus, CPUE of age‐0 walleye, CPUE of bluegill Lepomis macrochirus and CPUE of age‐3 and older white bass), each of which had a greater relative importance than the single abiotic variable (minimum daily air temperature during winter after hatching). Our findings improve the understanding of the recruitment of fishes in irrigation reservoirs and the relative roles of abiotic and biotic factors.     

A size‐age model based on bootstrapping and Bayesian approaches to assess population dynamics of Anguilla anguilla L. in semi‐closed lagoons

A size‐age modelling technique is presented for assessing the vital rates, stock and recruitment of eel populations in semi‐closed lagoons with fully monitored migration of silver eels. Data for yellow and silver European eels (Anguilla anguilla L.) were obtained in 2011 from the Comacchio lagoon (Italy). The analysis was performed in three steps: (i) correction of yellow eel data, which are affected by the fyke nets selectivity during samplings, (ii) estimation of survival curve, stock, recruitment and metamorphosis rates of the population (calibration using data from 2011) and (iii) validation of the model using the observed amount of silver eel migrating population of the next year. A bootstrap procedure was used to assess the level of uncertainty for each parameter using the 95% intervals of the highest posterior density distribution HPDD (Bayesian approach). The measured abundance of silver eels was 0.56 ind·ha^?1, while the yellow eel abundance and recruitment were estimated by the model for 2011 at 8.77 ind·ha^?1 and 5.99 ind. ha^?1 respectively. The model performance during validation was satisfactory as the observed total mass of migrating population of 2012 (3777 kg) was inside the 95% HPDD intervals (3197–3839 kg) of model's predictions. The estimated stocks and recruitment were at least ten times lower from the respective estimations of previous studies of 1989 highlighting the crucial conditions of the population. The proposed modelling approach can provide significant information about eel population conditions, facilitating the evaluation of a range of management options in the context of eel conservation plans.     

Spatio‐temporal,ontogenetic and interindividual variation of age‐0 diets in a population of yellow perch

Dietary niches of fishes have traditionally been evaluated at the population level, with diet pattern central tendencies compared spatio‐temporally among habitats and populations. More recently, however, studies have emphasised the importance of within‐population diet variation and niche partitioning. Several studies have examined diets of young yellow perch (Perca flavescens) at the population level and have described an ontogenetic transition from zooplankton to benthic prey during the first year of life. However, independent of ontogenetic diet shifts, intrapopulation variation of young yellow perch diets remains largely unexplored. We quantified patterns of diet composition in age‐0 yellow perch collected from Saginaw Bay, Lake Huron, USA during July–October, 2009 and 2010. We observed substantial variation in diet composition among individuals across and within sites, but found relatively weak evidence indicating an ontogenetic diet shift. Zooplankton were the dominant prey for age‐0 yellow perch on most occasions, and individual diets were composed primarily of either zooplankton (e.g. Daphnia spp., Calanoida) or benthic (i.e. Chironomidae larvae, Chydoridae) prey. These patterns were not simply attributable to differences in prey availability and ontogenetic diet shifts, because a) not only diet composition, but also prey selectivity (Chesson's α) varied among sites and b) individual and spatial diet differences were evident independent of ontogeny. Within‐cohort differences in diet composition may be an important, but often overlooked, phenomenon with implications for cumulative trophic interactions and intracohort growth and survival among young fish.