The timing of spring warming shapes reproductive effort in a warm-water fish: the role of mismatches between hepatic and gonadal processes

Spring-spawning fishes native to northern environments rely on both increasing temperature and lengthening photoperiod to cue reproduction and may thus be particularly sensitive to rapid warming earlier in the year while day lengths remain short. We investigated the reproductive response of pumpkinseed sunfish Lepomis gibbosus to spring warming commencing at a range of day lengths (9 – 15 hours), corresponding to various calendar days (January 10 – May 22). In both the laboratory and field, both male and female fish that experienced early warming while day lengths were <11 hours: 1) failed to initiate reproductive preparation in the liver before gonad development began, and 2) had reduced reproductive allocation. Analysis of published data on temperate fishes suggested that liver development prior to gonad development is widespread across warm-, cool-, and cold-water thermal guilds, though the precise phenology of liver relative to gonad development appears to vary widely among species. Together, our results point toward dampened reproductive preparation as a novel mechanism mediating reduced reproductive output in both warm- and cool-water fish following earlier spring warming.

Hydrological control of a floodplain subsidy to littoral riverine fish

Ecological subsidies have been hypothesized to be key factors affecting the dynamics of the recipient ecosystems. We assessed the impact of the flood regime on the assimilation of a trophic subsidy produced in the floodplain of a large fluvial lake, Lake Saint-Pierre (Quebec, Canada) on five invertivore littoral fish species (yellow perch (Perca flavescens), pumpkinseed (Lepomis gibbosus), bridle shiner (Notropis bifrenatus), golden shiner (Notemigonus crysoleucas), and banded killifish (Fundulus diaphanus)). We hypothesized that the incorporation of floodplain-derived carbon into fish biomass and individual fitness would increase in years with higher magnitude and longer duration floods. Studying four consecutive years with contrasting spring-flood events, we used a stable isotope mixing model to estimate floodplain contribution, and linear mixed models to analyze the impact of hydrology on floodplain contribution and fish body condition. Floodplain and main river’s invertebrates exhibited statistically distinct isotopic ratios (t test: p value < 0.001). Floodplain contribution and body condition were positively correlated with flooding intensity and duration for all species. Body condition was positively correlated with the assimilation of floodplain-subsidy for golden shiner and banded killifish. Our study identified flooding intensity as a main driver influencing the assimilation of floodplain-derived carbon by littoral fish and their fitness in a large river ecosystem.

Single target acuity in the common sunfish (Lepomis gibbosus)

Vision is considered to contribute to foraging, territorial, and reproductive behavior in sunfish. In these contexts, sunfish need to perceive single targets, such as prey items or body markings from either conspecifics or individuals of other sunfish species, from some distances. We determined the single target acuity of six common sunfish in a behavioral experiment to assess whether the visual abilities of sunfish correspond with behavioral observations or reactive distance measures and thus to assess the limits of vision regarding the mentioned behaviors. Single target acuity for full-contrast single targets amounted to 0.17 (0.13 - 0.32) deg. When contrast was reduced to Weber contrasts of 0.67 and 0.41, single target acuity dropped to 0.34 (0.31 - 0.37) deg, and finally to 0.42 (0.34 - 0.54) deg. Single target acuity would thus allow common sunfish to perceive biologically relevant stimuli at reasonable distances even when contrast is reduced.

Nutrition Physiology of Juveniles Individuals of Pumpkinseed Lepomis gibbosus (Linnaeus, 1758) from the Samara Bay (Ukraine)

The article presents the results of studies physiology of nutrition of juveniles individuals of pumpkinseed Lepomis gibbosus (Linnaeus, 1758) from the Zaporizhzhia (Dnipro) reservoir. histological structure, morphometric parameters of digestive system and nutrition biology were investigated. The material for work were collected during scientific research in June-July 2016–2017. The ichthyological sampling was carried out in the Samara Bay of the Zaporizhzhia (Dnipro) reservoir. Researches of structure of digestive system were conducted using histological methods, researches of nutrition were conducted using ichthyological and hydrobiological methods The height of the intestinal epithelium of the pumpkinseed`s juveniles varies from 15.5 microns to 51.9 microns and on average is 32.59 ± 9.03 microns, the area of secretory goblet cells of the intestine reaches 198.61 ± 36.55 μm2. It was revealed that the pumkinseed’s juveniles only feed on phytoplankton. Research results can be useful for further study on the fish nutrition, especially sexual matured. Also, nutrition studies can help to find biomeliorative methods to combat the pumpkinseed, because the species is in competition with industrially valuable species of fish for fodder.

Host diet and parasitic helminth infections within native, established and introduced fish of Algonquin Park

Freshwater fish biodiversity loss has been attributed to many reasons, including invasive species infectious diseases. I examined 112 invasive Rock Bass (Ambloplites rupestris), 59 established Smallmouth Bass (Micropterus dolomieu), and 60 native Pumpkinseed sunfish (Lepomis gibbosus) from 8 different lakes in Algonquin Park, ON, Canada to evaluate their endohelminth parasites. My results indicate that established and native fish are not only more likely to be infected with trophically-transmitted parasites such as cestodes (tapeworms) and acanthocephalans (thorny-headed worms) than invasive Rock Bass, but they also have a higher infection intensity and greater diversity of endohelminths. There was also a significant difference between the three fish species with respect to non-trophically transmitted larval trematodes (flatworms), which reflect the habitat of fish. Along with host size, I examined fish diet and habitat use to demonstrate how the ecology of different species influences their probability of infection, parasite communities, and possible ease of establishment in novel environments.

Host diet and parasitic helminth infections within native, established and introduced fish of Algonquin Park

Freshwater fish biodiversity loss has been attributed to many reasons, including invasive species infectious diseases. I examined 112 invasive Rock Bass (Ambloplites rupestris), 59 established Smallmouth Bass (Micropterus dolomieu), and 60 native Pumpkinseed sunfish (Lepomis gibbosus) from 8 different lakes in Algonquin Park, ON, Canada to evaluate their endohelminth parasites. My results indicate that established and native fish are not only more likely to be infected with trophically-transmitted parasites such as cestodes (tapeworms) and acanthocephalans (thorny-headed worms) than invasive Rock Bass, but they also have a higher infection intensity and greater diversity of endohelminths. There was also a significant difference between the three fish species with respect to non-trophically transmitted larval trematodes (flatworms), which reflect the habitat of fish. Along with host size, I examined fish diet and habitat use to demonstrate how the ecology of different species influences their probability of infection, parasite communities, and possible ease of establishment in novel environments.