Identifying across-system sources of variation in a generalist freshwater fish: correlates of total and size-specific abundance of yellow perch

Abstract –  Variation in fish abundance across systems presents a challenge to our understanding of fish populations because it limits our ability to predict and transfer basic ecological principles to applied problems. Yellow perch ( Perca flavescens ) is an ideal species for exploring environmental and biotic correlates across system because it is widely distributed and physiologically tolerant. In 16 small, adjacent systems that span a wide range of environmental and biotic conditions, yellow perch were sampled with a standard suite of gear. Water quality, morphometry, vegetation, invertebrates and fish communities were concurrently measured. Multimodel inference was used to prioritise regressors for the entire yellow perch sample and three size groups (35–80, 81–180, ≥181 mm TL). Across systems, pH and fish richness were identified as the key drivers of yellow perch abundance. At very low pH (<4.0), few fish species and few yellow perch individuals were found. At ponds with moderately low pH (4.0–4.8), numbers of yellow perch increased. Ponds with high pH (>4.8) had many other species and few yellow perch. Similar patterns for pH and fish community were observed for the two largest-size classes. Negative interactions were observed between the medium- and large-sized yellow perch and between the largest and smallest yellow perch, although interspecific interactions were weaker than expected. This examination of variability for an indicator species and its component-size classes provides ecological understanding that can help frame the larger-scale sampling programs needed for the conservation of freshwater fish.     

Is scuba sampling a relevant method to study fish microhabitat in lakes? Examples and comparisons for three European species

Abstract – We compared fish microhabitat use patterns in the littoral zone of a lake using a new direct method (point abundance sampling by scuba, PASS) and the widely used point abundance sampling by electrofishing technique (PASE). We collected microhabitat data for age 0+ roach ( Rutilus rutilus L.), perch ( Perca fluviatilis L.), and pike ( Esox lucius L.). The two methods yielded different results for fish assemblage structure and microhabitat patterns. Using PASE, fish were mainly found in "shelter habitats" such as shallow waters and dense vegetation. It is likely that this behavior is caused by the disturbance of the observer stamping around. Using PASS, fish escapement behavior was rarely observed. Therefore, we concluded that this direct and nondestructive sampling technique can be used to provide an accurate microhabitat estimation of a fish community and is assumed to be more suitable than PASE for fish habitat studies.     

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.     

Prey selection and growth in 0+ Eurasian perch Perca fluviatilis L. in littoral zones of seven temperate lakes

We studied the relationships between the planktonic food base and feeding patterns of juvenile mid-summer/early autumn Eurasian perch Perca fluviatilis L., a common predatory freshwater fish in large parts of Europe and Asia. The feeding of 0+ perch was studied during summer and autumn in littoral habitats of seven lakes with different environmental conditions – four Latvian (Auciema, Riebinu, Vārzgūnes, Laukezers) and three Estonian (Kaiavere, Prossa and Akste) lakes. Simultaneously, the abundance, biomass and structure of zooplankton communities were examined. We focused on the littoral areas because many studies in lakes suggest that littoral habitats are particularly important for 0+ fish growth and survival. We were interested in the question: can the diet and growth of 0+ perch be explained by zooplankton community structure? We also presumed that if the amount of zooplankton is low, more benthic invertebrates will be consumed by 0+ perch. Opposite to expectations, we found that zooplankton always counted for over 90% of diet biomass in perch. There were also clear correlations between the zooplankton biomass in a given lake, the zooplankton biomass in 0+ perch stomachs, and the fish growth rate. The study also suggested that nutrient enrichment can positively impact the 0+ perch feeding conditions in lakes.     

Fine‐scale movement ecology of a freshwater top predator,Eurasian perch (Perca fluviatilis), in response to the abiotic environment over the course of a year

Fine‐scale underwater telemetry affords an unprecedented opportunity to understand how aquatic animals respond to environmental changes. We investigated the movement patterns of an aquatic top predator, Eurasian perch (Perca fluviatilis), using a three‐dimensional acoustic telemetry system installed in Kleiner Döllnsee (25 ha), a small, shallow, mesotrophic natural lake. Adult piscivorous perch (N = 16) were tagged and tracked in the whole lake at a minimum of 9‐s intervals over the course of one year. Perch increased swimming activity with higher water temperature and light intensity. Air pressure, wind speed and lunar phase also explained perch movements, but the effects were substantially smaller compared to temperature and light. Perch showed a strong diel pattern in activity, with farther swimming distances and larger activity spaces during the daytime, compared to the night‐time. To investigate the influence of prey distribution, we sampled the prey fish in both littoral and pelagic zones in both day and night monthly using gill nets. We found that the prey fish underwent diel horizontal migration, using the littoral zone during the day and the pelagic zone during the night. However, perch showed the opposite patterns, suggesting either that the prey fish avoided predation risk or that the horizontal diel migration of perch was driven by other mechanisms. Our results collectively suggest that the movement ecology of piscivorous perch is mainly governed by a foraging motivation as a function of abiotic variables, especially temperature and light.     

The role of oceanographic conditions and plankton availability in larval fish assemblages off the Catalan coast (NW Mediterranean)

In the northwestern Mediterranean, most fish species reproduce in early summer and fewer in the autumn mixing period. This study analyses and compares larval fish assemblages (LFA) in both seasons, and is the first attempt to characterize LFA structure for the autumn period. We analyze horizontal and vertical distribution of fish larvae and the micro- and mesozooplankton biomass and abundance of the main zooplankton groups. The oceanographic situation was analyzed through the study of data from CTD, Nν-Shuttle and ADCP surveys. LFA were determined by ordination analyses based on larval abundance, and the relationships between larval assemblages and environmental variables were investigated through canonical correspondence analysis. The importance of some hydrographic variables (temperature, salinity and stability of the water column), current fields (along-shelf and across-shelf transport) and the abundance of zooplankton are discussed as important factors shaping the structure of larval assemblages. In early summer, LFA were mainly structured by a combination of bathymetry and trophic components, although sea surface temperature also played a role in shaping the horizontal larval distributions. In autumn, trophic variables were the main factors influencing the shelf-dwelling species assemblage. Larvae of oceanic species, on the other hand, were not related to trophic variables but were more affected by current fields.     

The movement pattern and density distribution of perch, Perca fluviatilis L., in a channelized lowland river

Abstract. The movement pattern and the abundance of perch, Perca fluviatilis L., were studied in the Kleine Nete, a eutrophic, canalized lowland river in north Belgium. Since the behaviour of perch is strongly affected by habitat type, two kinds of river section were chosen, based on physical characteristics: homogeneous sections with regard to depth, bottom type and current speed; and heterogeneous sections with a riffle and pool pattern. The fish were caught by electrofishing and all perch larger than 10 cm were marked individually. The population densities were much higher in the heterogeneous parts. In these sections about 30% of marked perch stayed within a home range, while in the homogeneous sections all were mobile. The older individuals showed a stronger tendency to accept a home range than the 1- or 2-year-old perch. This difference may be explained by different behaviour: young perch live in small schools, while older perch are often solitary. The low densities and the high mobility of perch in the homogeneous river sections indicate that these parts of the river are not a suitable habitat for perch. Habitat improvement of the homogeneous sections wilt probably result in higher overall population densities.     

Perch (Perca fluviatilis) as an indicator species for structural degradation in regulated rivers and canals in the lowlands of Germany

Abstract— Simple morphological characteristics and fish assemblage data were collected in representative numbers from 12 inland waterways in the northeastern lowlands of Germany between 1992 and 1995. Fish abundance data were pooled and classified into three main groups: perch Perca fluviatilis (L.), roach Rutilus rutilus (L.) and other species. Spearman rank correlations between fish abundance and type of embankment revealed that perch showed a statistically significant numerical dominance in waterways consisting predominately of an artificial shoreline, suggesting that perch may be used as an indicator of the structural degradation of watercourses.     

Diet dynamics of the juvenile piscivorous fish community in Spirit Lake, Iowa, USA, 1997–1998

Abstract – We assessed temporal dynamics and variation among species and age-classes in the diets of age 0 and age 1 piscivorous fish species in Spirit Lake, Iowa, USA during 1997 and 1998. Species included walleye Stizostedion vitreum , yellow perch Perca flavescens , smallmouth bass Micropterus dolomieui , largemouth bass Micropterus salmoides , black crappie Pomoxis nigromaculatus and white bass Morone chrysops. Thirty taxa were identified in diets, including 12 species of fish. We found dramatic differences in diets among species, among age-classes within species and over time. Walleye, largemouth bass, smallmouth bass and white bass were piscivorous at age 0. Black crappie began piscivory at age 1. Yellow perch also began piscivory at age 1, but fish were a very small fraction of age-1 diets. The primary temporal pattern, seen in several species and age-classes, was an increase in piscivory from spring to fall. This pattern was due to the lack of small, age-0 prey fish in spring. Although some patterns were evident, the taxonomic composition of the diets of all species was highly variable over time, making generalizations difficult. A surprising result was the absence of yellow perch in the diet of age-0 walleye, despite their abundance in Spirit Lake and prominence in diets of age-1 walleye and other age 1-piscivores. Age-0 yellow perch were consistently too large to be eaten by age-0 piscivores, which preyed primarily on invertebrates and smaller fish such as johnny darters Etheostoma nigrum and age 0 bluegill Lepomis macrochirus. This finding suggests that predator-prey interactions and resulting population dynamics may be quite different in Spirit Lake than in other systems dominated by walleye and yellow perch.     

Seasonal distribution of the Indo-Pacific humpback dolphins: Implications for coastal habitat management

1. Organisms utilize suitable habitat patches wherein they optimize fitness. For marine megafauna such as cetaceans, foraging is generally the explanation for their utilization distribution. However, an explicit link between cetaceans' distribution and spatio-temporal pattern of food resource is usually lacking.
2. The Indo-Pacific humpback dolphin (Sousa chinensis; VU listed in the IUCN Red List) inhabits the coastal waters from south-east China to eastern India. Seasonal distribution of the humpback dolphin was explored in the northern Beibu Gulf, China. Sightings of the humpback dolphin were systematically collected at monthly intervals from 2012 winter till 2018 spring and used to derive distribution patterns from kernel density estimates. Satellite remotely sensed net primary productivity (NPP) and bathymetry were used to present oceanographic characteristics in the study region.
3. Seasonal variations were observed in oceanographic characteristics and spatial distribution of the humpback dolphin. Although the core distribution area of the humpback dolphin showed seasonal expansion and contraction, it had consistently higher NPP and shallower depth than the survey range throughout the seasons.
4. Our findings indicate a clear profile of these two oceanographic characteristics (i.e. NPP and bathymetry) in the humpback dolphin's core distribution area. Food resource utilization could play an important role in the humpback dolphin's distribution within the study site. The seasonal dynamics imply that not only food abundance, but also efficiency in accessing/capturing the prey may affect distribution of the humpback dolphin.
5. In the study site, human activities that can change regional topography and productivity of the coastal water through land reclamation, dredging, sand mining and bottom trawling, should be mitigated, regulated or avoided. Proactive conservation should incorporate catchment management of the main rivers to address potential sediment and nutrient load into the estuary to protect local habitat configuration in terms of NPP and bathymetry.

     

Challenge studies of European stocks of redfin perch, Perca fluviatilis L., and rainbow trout, Oncorhynchus mykiss (Walbaum), with epizootic haematopoietic necrosis virus

A challenge model for comparison of the virulence of epizootic haematopoietic necrosis virus (EHNV) to European stocks of redfin perch, Perca fluviatilis L., and rainbow trout, Oncorhynchus mykiss (Walbaum), was tested. The model investigated intraperitoneal (IP), bath and cohabitation routes at 10, 15 and 20 °C for 5–6 g fish and 15 °C for 20 g perch. In the IP challenges of perch, significant mortality occurred at 15 °C and 20 °C. In challenge trials for rainbow trout, significant mortalities were observed in IP and bath challenges at 20 °C. The mortality observed in IP challenged 20 g perch was not significantly different from that recorded for 6 g fish challenged IP. No significant mortality was observed in any other treatment groups. Re-isolation of ranavirus was confirmed by IFAT and was consistently associated with dead or moribund fish in the trial groups challenged with EHNV. The findings indicate that EHNV does not pose a high risk for wild perch and trout populations in Europe by natural exposure. Mortality appears to be primarily a function of environmental factors, with temperature playing an important role, and not just the presence of the virus in the fish.     

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.     

The effects of perch, Perca fluviatilis L., and bronze bream, Abramis brama (L.), on insect emergence and benthic invertebrate abundance in experimental ponds

Abstract The effects of perch, Perca fluviatilis L., and bronze bream, Abramis brama (L.), predation on the production of insects emerging at the water surface and the autumn biomass of benthic macro-invertebrates were assessed in a series of experimental ponds. The study attempted to discover whether fish affect food availability for diving and dabbling ducks in freshwater habitats. Ten ponds (bisected by fine netting) were used for the study: one was left totally fish-free, whilst one half of each of three groups of three ponds was stocked with either perch, bream or perch plus bream. The relative abundance of emerging insects (mainly Chironomidae) was significantly reduced in two perch ponds, two perch + bream ponds and two bream ponds. The autumn standing crops of benthic macroinvertebrates were significantly reduced in one perch pond, three bream ponds and one perch plus bream pond. These results support findings of a contemporaneous large bio-manipulation experiment carried out in two adjacent lakes. During the biomanipulation studies, aquatic invertebrate standing stocks greatly increased after the removal of fish and decreased following restocking.     

胶州湾外南沙水域渔业资源与文昌鱼数量调查评估及其栖息环境保护

应用扫海面积法，并根据鱼类和文昌鱼栖息特点，采用了不同拖网取样方式，对胶州湾外南沙周围24km^2水域5、6月渔业资源数量与文昌鱼(Branchiostoma belcheri Gary)数量进行了调查评估。5月捕获的鱼类共28种，总资源量275479kg，其中玉筋鱼居第1位，资源量265200kg。捕获的无脊椎动物共13种，总资源量3489kg。6月文昌鱼数量约为18720000尾。同时，还指出了栖息环境面临的问题以及保护栖息环境的重要性和必要性。     

Effects of genetic strain and holding facility on the characteristics of alkaline phosphatase and brush border enzymes in silver perch (Bidyanus bidyanus)

The activity of the enzymes located in the digestive tract (pyloric caeca and intestine) in two strains and F₁ crosses of the Australian freshwater fish silver perch [Murray River (M) and Cataract Dam (C)] was evaluated. The effect of the fish holding system (cages or ponds) on the activity of alkaline phosphatase (AP) and the brush border enzymes: maltase, leucine amino peptidase (LAP) and γ‐glutamyl transferase (γ‐GT) was examined. The enzymatic activity was tested in three intestinal sections: the pyloric caeca, upper and lower intestine. All the tested enzyme activities were influenced by an interaction between the intestinal section and the strain or cross of silver perch. For fish maintained in ponds, there were two distinct enzymatic activity patterns, one for the pure strains (C × C and M × M) and one for the crosses (C × M and M × C). Significantly higher (P<0.05) enzymatic activities of the crosses compared with the pure strains were particularly noticeable in the pyloric caeca. In fish held in cages, there was a significantly higher (P<0.05) enzymatic activity in the pyloric caeca of the C × C strain. The total enzymatic activities in the fish reared in the ponds were significantly higher (P<0.05) than those in the fish held in cages. The results of the present investigation confirm that the different genetic background of the silver perch in the Murray River and in the Cataract Dam influences the activity of the brush border digestive enzymes. This activity also varies between maintenance systems.     

Changes in yellow perch (Perca flavescens) growth associated with the establishment of a walleye (Stizostedion vitreum) population in Canadarago Lake, New York (USA)

Abstract – Piscivorous fish can affect prey growth in two ways: directly by reducing prey density and indirectly by inducing predator-avoidance behaviors. We investigated these two pathways in yellow perch ( Perca flavescens ) growth responses to walleye ( Stizostedion vitreum ) stocking in Canadarago Lake, New York (USA) using a 25-year time series. Before walleye stocking, yellow perch growth rate was low and independent of body size. As walleye abundance increased, yellow perch growth increased and became size-dependent. The switch to size-dependent growth occurred in 1 year, indicating a rapid behavioral response to predators. Mean growth rate increased more gradually and was linearly related to walleye density, indicating a slower numerical effect of walleye on yellow perch densities. Although the net effect was an increase in perch growth, small perch growth initially decreased as walleye became established. Therefore, the combination of numerical and behavioral effects produced a complex pattern of size-dependent changes in growth of yellow perch.     

Hydroacoustic assessment of young-of-year perch, Perca fluviatilis, population dynamics in an oligotrophic lake (Lake Annecy, France)

Abstract  A cohort of perch, Perca fluviatilis (L.) was monitored from hatching to first winter in the oligotrophic Lake Annecy, France, by combining hydroacoustic and direct capture methods (fish plankton net and pelagic trawl). The total stock of pelagic fish increased by a factor of 10 during the season, reaching a maximum in August and decreasing in autumn. Juvenile perch were mainly pelagic, being aggregated into schools in the daytime and dispersed at night. Migration of young-of-year (Y-O-Y) perch to the pelagic zone of Lake Annecy in late spring did not significantly affect zooplankton population abundance. It did, however, result in changes in zooplankton vertical distribution, with Daphnia remaining deeper in the water column. The increase in Y-O-Y biomass during summer was possibly associated with collapse of the Daphnia population by late July, and copepods one month later.     

Long-term development of fish populations in the Římov Reservoir

Abstract  The inshore fish community of the Římov Reservoir in the Czech Republic was evaluated over 21 years using shore seining at night. The development of the fish community was divided into two separate phases: a highly dynamic and unstable phase dominated by perch, Perca fluviatilis L., was replaced by an extremely stable cyprinid phase dominated by roach, Rutilus rutilus (L.), and bream, Abramis brama (L.). The abundance of both these species oscillated during the cyprinid phase, but with decreasing amplitude. The proportion of piscivorous fish species such as asp, Aspius aspius (L.), pike, Esox lucius L., and pikeperch, Sander lucioperca (L.), increased slightly with time but remained low. The biomass of large Cladocera was negatively correlated with fish biomass only during the perch phase. The Shannon–Weaver index of diversity increased during the fish community succession, mainly because of greater evenness amongst the species.     

Spatial and temporal patterns in summer ichthyoplankton assemblages on the eastern Bering Sea shelf 1996–2000

Larval and early juvenile fishes were sampled from the eastern Bering Sea (EBS) shelf during summer from 1996 to 2000. Data from these collections were used to examine spatial and temporal patterns in species assemblage structure and abundance. Cluster analyses based on Bray–Curtis dissimilarity coefficients were used to group species and stations according to similar abundance and species composition. Ordination techniques were used to verify groupings, and a non‐parametric stepwise procedure using a Spearman correlation coefficient (BIO‐ENV) was used to relate groupings to predominant environmental variables. These approaches revealed a pattern of station groupings that were generally related to bathymetry in 1996, 1997, 1999, and 2000, although no obvious relationship to geographic boundaries was observed in 1998. Significant differences in species associations were observed in 1997 and 1998, and depressions in abundance were also noted among many species between 1997 and 1999. A regional, full primitive equation model was used to simulate float trajectories on the EBS shelf in each year to better relate fish distributional observations to prevailing current patterns. Model results indicated general variations in flow in several years, although 1998 stood out with stronger northeast flow than in any of the other years examined. Observed disruptions of larval and early juvenile fish assemblages could be related to the strong El‐Niño event of 1997–98 in the EBS. If this idea is confirmed, our study suggests that larval and juvenile fish are sensitive and respond relatively quickly (1–2 yr) to environmental perturbations, and as such, may be timely indicators of environmental change.     

No reason for keeping 0+ perch (Perca fluviatilis L.) with the prey fish

Growth and survival of 0+ perch were studied in 4 ponds with the topmouth gudgeon (Pseudorasbora parva) and without it. In the end of April, all ponds were stocked by free-swimming perch larvae (120,000 ind ha^?1). In June, topmouth gudgeon was introduced as forage fish (40 kg ha^?1) into two of the experimental ponds. Topmouth gudgeon significantly influenced neither the total abundance of zooplankton nor the abundance of its groups (Rotifera, Cladocera, Copepoda). The most important food item for perch (TL > 29 mm) was macroinvertebrates (especially Chironomidae). In the ponds with topmouth gudgeon, copepods and cladocerans were more important than in ponds without it. Specific growth rate of perch was 0.01 mm day^?1 in all ponds. Final mean total length (TL ± SD) of perch was 73 ± 13 and 70 ± 6 mm in the ponds with topmouth gudgeon and without it, respectively. Only 1 % of the perch reached higher TL than that recorded in the ponds without the topmouth gudgeon. Survival rate of perch varied from 12 to 36 % depending on ponds. Piscivory was recorded in all ponds from the age of 57 days (post-stocking); however, perch siblings were preferred to topmouth gudgeon. The highest asymptotic growth (L∞ = 88 mm) was calculated in the pond stocked with topmouth gudgeon. This corresponded with the highest cannibalism and lowest survival rate (12 %). Perch growth rate increased till 42–53 days of perch age and then started to decrease. There was no significant influence of potential prey fish (topmouth gudgeon) on the growth of 0+ perch; however, two size cohorts were found in the ponds with the topmouth gudgeon. Presence or absence of littoral macrophytes seems to be more substantial for rearing perch in ponds than stocking with the prey fish.