Growth portfolios buffer climate-linked environmental change in marine systems.

Large-scale, climate-induced synchrony in the productivity of fish populations is becoming more pronounced in the world's oceans. As synchrony increases, a population's "portfolio" of responses can be diminished, in turn reducing its resilience to strong perturbation. Here we argue that the costs and benefits of trait synchronization, such as the expression of growth rate, are context dependent. Contrary to prevailing views, synchrony among individuals could actually be beneficial for populations if growth synchrony increases during favorable conditions, and then declines under poor conditions when a broader portfolio of responses could be useful. Importantly, growth synchrony among individuals within populations has seldom been measured, despite well-documented evidence of synchrony across populations. Here, we used century-scale time series of annual otolith growth to test for changes in growth synchronization among individuals within multiple populations of a marine keystone species (Atlantic cod, Gadus morhua). On the basis of 74,662 annual growth increments recorded in 13,749 otoliths, we detected a rising conformity in long-term growth rates within five northeast Atlantic cod populations in response to both favorable growth conditions and a large-scale, multidecadal mode of climate variability similar to the East Atlantic Pattern. The within-population synchrony was distinct from the across-population synchrony commonly reported for large-scale environmental drivers. Climate-linked, among-individual growth synchrony was also identified in other Northeast Atlantic pelagic, deep-sea and bivalve species. We hypothesize that growth synchrony in good years and growth asynchrony in poorer years reflects adaptive trait optimization and bet hedging, respectively, that could confer an unexpected, but pervasive and stabilizing, impact on marine population productivity in response to large-scale environmental change.

The Capacity of Freshwater Ecosystems to Recover from Exceedences of Aquatic Life Criteria.

In the United States, national chemical water quality criteria for the protection of aquatic life assume that aquatic ecosystems have sufficient resiliency to recover from criteria exceedences occurring up to once every 3 years. This resiliency assumption was critically reviewed through two approaches: (1) synthesis of case studies, and (2) population modeling. The population modeling examined differences in recovery of species with widely different life histories. One invertebrate (Hyalella azteca) and four fish species were modeled (fathead minnow, brook trout, lake trout, and shortnose sturgeon) with various disturbance magnitudes and intervals. The synthesis of ecosystem case studies showed generally faster recoveries for insect communities rather than fish, and recoveries from pulse (acute) disturbances were often faster than recoveries from press (chronic) disturbances. When the recovery dataset excluded severe disturbances that seemed unrepresentative of common facility discharge upsets that might cause criteria exceedences, the median recovery time was 1 year, 81% of the cases were considered recovered within 3 years, and 95% were considered recovered within 10 years. The modeling projected that short-lived fish species with high recovery times could thrive despite enduring 50% mortality disturbances every other year. However, long-lived fish species had longer recovery times and declined under the one disturbance every 3 years scenario. Overall, the analyses did not refute the long-standing judgements that 3 years is generally sufficient for recovery from nonrepetitive, moderate intensity disturbances of a magnitude up to 2× the chronic criteria in waters without other pollution sources or stresses. However, these constraints may not always be met and if long-lived fish species are a concern, longer return intervals such as 5-10 years could be indicated. Environ Toxicol Chem 2022;41:2887-2910. Published 2022. This article is a U.S. Government work and is in the public domain in the USA.

Mixed interactions among life history stages of two harvested related species.

Climate change and harvesting can affect the ecosystems' functioning by altering the population dynamics and interactions among species. Knowing how species interact is essential for better understanding potentially unintended consequences of harvest on multiple species in ecosystems. I analyzed how stage-specific interactions between two harvested competitors, the haddock (Melanogrammus aeglefinus) and Atlantic cod (Gadus morhua), living in the Barents Sea affect the outcome of changes in the harvest of the two species. Using state-space models that account for observation errors and stochasticity in the population dynamics, I run different harvesting scenarios and track population-level responses of both species. The increasing temperature elevated the number of larvae of haddock but did not significantly influence the older age-classes. The nature of the interactions between both species shifted from predator-prey to competition around age-2 to -3. Increased cod fishing mortality, which led to decreasing abundance of cod, was associated with an increasing overall abundance of haddock, which suggests compensatory dynamics of both species. From a stage-specific approach, I show that a change in the abundance in one species may propagate to other species, threatening the exploited species' recovery. Thus, this study demonstrates that considering interactions among life history stages of harvested species is essential to enhance species' co-existence in harvested ecosystems. The approach developed in this study steps forward the analyses of effects of harvest and climate in multi-species systems by considering the comprehension of complex ecological processes to facilitate the sustainable use of natural resources.

Are current tissue-based selenium guidelines and criteria overly protective of freshwater fish populations? A critical review with recommendations.

Several decades after selenium impacts on wild fish populations were observed in freshwater reservoirs receiving fly ash effluents from electric power facilities at Belews Lake and Hyco Reservoir (North Carolina, USA), developments in selenium (Se) toxicology have led to a greater understanding of Se effects on freshwater fish. These latter advancements have allowed regulatory agencies in several jurisdictions to develop tissue-based toxicity benchmarks for the protection of aquatic life. These benchmarks were generally derived from datasets encompassing multiple fish species and designed to protect the most sensitive species (US Environmental Protection Agency [EPA] water quality criteria). Safety factors have been applied in the development of some Canadian guidelines (British Columbia [BC]), resulting in guidelines that appear to be overly conservative. The present study addresses the question, "Are current tissue-based selenium guidelines and criteria overly protective of freshwater fish populations?" A literature review was conducted of studies in which Se was the primary constituent of concern, to compare tissue concentrations and results of fish population metrics and deformity assessment studies with current regulatory thresholds for the protection of aquatic life in the United States and Canada. EPA fish tissue-based Se criteria were found to be protective of fish populations and, at times, overly protective. Canadian water quality guidelines for Se (BC Ministry of Environment and Climate Change Strategy [BCMOECCS], Environment and Climate Change Canada [ECCC]) were consistently found to be overly protective, especially for benchmarks in which safety factors were used to derive those guidelines. In addition to a synthesis of the results of these studies, various limitations of the reviewed studies are discussed, and recommendations for future studies are proposed. Integr Environ Assess Manag 2022;18:622-630. © 2021 SETAC.

Effects of the synthetic estrogen 17α-ethinylestradiol on Heterandria formosa populations: Does matrotrophy circumvent population collapse?

Feminization responses have been observed in some wild populations of fish living in rivers and streams, some of which have been shown to arise as a consequence of exposure to sewage treatment (STP) effluent discharges and the endocrine disrupting chemicals (EDCs) they contain which mimic or antagonize the actions of steroid hormones. The synthetic estrogen, 17α-ethinylestradiol (EE2), commonly used in oral contraceptives, is present in surface waters receiving STP effluents at concentrations ranging from non-detectable to 5 ng/L. Despite extensive evidence that EE2 negatively affects the reproductive health of fishes, relatively little is known about effects at the population level - and especially so for live-bearing fishes. To investigate the potential for such impacts, populations of the least killifish (Heterandria formosa) were exposed to 0 or 5 ng/L EE2. Exposures were started with newborn fish and continued for seven months. Chronic exposure to 5 ng/L EE2 caused significant reductions in population size, in abundances of newborns and males, and in population growth rates. The exposure also resulted in a female-biased sex ratio. However, individuals' survival rates were not affected. This study showed that chronic exposure to 5 ng/L EE2 negatively affected population dynamics in a live-bearing fish, demonstrating that the levels of EE2 detected near STPs have the potential to impact wild populations of these fish.

Analysis of a Length-Structured Density-Dependent Model for Fish.

We present a length-structured matrix model for fish populations in which the probability that a fish grows into the next length class is a decreasing nonlinear function of the total biomass of the population. We present mathematical results classifying the dynamics that this density-dependent model predicts. We illustrate these results with numerical simulations for an invasive white perch population and show how the mathematical results can be used to predict the persistence and/or boundedness of the population as well as an equilibrium structure that is dominated by small fish. We illustrate the results with management recommendations for an invasive white perch population.

Evaluation of Lethal Fish Sampling and the Nonlethal Alternative Under the Canadian Metal and Diamond Mining Environmental Effects Monitoring Program.

The Environmental Effects Monitoring (EEM) program, federally mandated to metal and diamond mines and mills in Canada, aims to ensure that fish, fish use, and their environment are sufficiently protected by the Metal and Diamond Mining Effluent Regulations (MDMER). Concerns have been raised regarding lethal fish sampling conducted for the program and the potential risk to fish populations. This study endeavored to calculate the extent of fish sacrificed during lethal EEM fish surveys to provide a more informed characterization for stakeholders. By extrapolating data from 28 studies conducted at 8 metal mines in Saskatchewan between 2004 and 2017, it was conservatively estimated that 60 060 ± 19 978 fish have been sacrificed for the program nationwide since its promulgation in 2002. This is almost 2 times greater than guidance recommendations due to numerous factors. Challenges faced when implementing the nonlethal fish population survey alternative were also evaluated, and some of these included data interpretation inconsistencies due to the lack of critical effect sizes (CES) included in the regulations for nonlethal effect endpoints, and reliance on capturing young of the year fish to assess the prescribed effect endpoints. Finally, a case study conducted to evaluate the congruity of lethal and nonlethal fish population survey results identified that the effect endpoints often produced conflicting conclusions for the same response variable. Ultimately, this study highlights that in order to strengthen and promote the use of nonlethal fish sampling as an alternate to the current standard of conducting lethal fish population surveys under the EEM program, the effect endpoints, study designs, and adoption of CES need to be thoroughly evaluated and included in the MDMER. If nonlethal sampling designs adequately provide the required data and meet program objectives, then there would be no need to continue sacrificing fish for the Canadian metal and diamond mining EEM program. Integr Environ Assess Manag 2019;00:1-10. © 2019 SETAC.

Developing Triggers for Environmental Effects Monitoring Programs for Trout-Perch in the Lower Athabasca River (Canada).

Baseline variations in trout-perch energy use (growth, gonad size) and energy storage (condition, liver size) were characterized between 2009 and 2015 in 8 reaches of the Athabasca River (AB, Canada), including 2 reaches upstream of the city of Fort McMurray (AB, Canada) and 6 reaches downstream of Fort McMurray among existing oil sands operations. Generalized linear models, used to account for background variation, indicated that fork length, gonad size, and liver size decreased, whereas body weight increased, in relation to river discharge, for both male and female trout-perch. Air temperature was positively correlated with liver size and negatively correlated with gonad size and body weight for females, but only positively correlated with gonad weight for males. These linear models explained approximately 20 to 25% of the variation in adjusted body size, and upward of 80% of the variation in adjusted body weight, liver weight, and gonad weight. Residuals from linear models were used to estimate normal ranges of variation for each of the fish population performance measures. Combined, the models and normal ranges can be used to assess subsequent monitoring data, providing potential triggers for follow-up monitoring activities. Environ Toxicol Chem 2019;38:0-0. Environ Toxicol Chem 2019;38:1890-1901. © 2019 SETAC.

The relation between polychlorinated biphenyls and population metrics of 4 species of fish from the upper Hudson River, New York, USA.

In the upper Hudson River, New York, USA, fish were exposed to polychlorinated biphenyls (PCBs) from the 1940s to 1977, and PCBs still persist in this environment. Yellow perch (Perca flavescens), brown bullhead (Ameiurus nebulosus), smallmouth bass (Micropterus dolomieu), and largemouth bass (M. salmoides) were collected annually from 2003 to 2009 from 1 control site upstream of the PCB discharge locations and from 2 sites downstream from where PCBs were released. Fish PCB concentrations were estimated, and 3 population metrics were examined: 1) relative abundance, 2) weight-to-length ratio, and 3) growth. Normalized lipid-based PCB concentrations at the 2 PCB exposure pools averaged approximately 100 to 600 µg/g. Estimated relative abundances with electrofishing were higher for largemouth bass, smallmouth bass, and brown bullhead at PCB exposure sites compared to the control site; but yellow perch were more abundant at the control site. Weight to length ratios varied among sites and species, but no consistent pattern was evident in relation to PCBs at the population level or for individual fish. Growth rates for yellow perch and brown bullhead were similar among sites. Largemouth bass growth was slightly higher at the control site compared to the 2 PCB sites, but smallmouth bass growth was much higher at the PCB sites compared to the control site. We could not detect any relation or influence of PCBs on the 3 population metrics that we examined. the present results corroborated those of previous investigations concerning the effects of PCBs on fishes. We recommend stronger consideration of the biological impacts of PCBs at the population level when conducting risk assessments. Environ Toxicol Chem 2019;38:329-339. © 2018 SETAC.

Ingestion of plastic by fish: A comparison of Thames Estuary and Firth of Clyde populations.

This study compared plastic ingestion between pelagic and benthic fish populations from two UK watersheds: the Thames Estuary and the Firth of Clyde. The alimentary canals of 876 individuals were examined. Of twenty-one estuarine species investigated, fourteen ingested plastics, including predator (fish) and prey (shrimp) species. Overall, 32% of organisms ingested plastic, mostly fibres (88% of total plastics). More flatfish (38%) ingested plastics than other benthic species (17%). In the Thames, more plastic was ingested by pelagic species (average number of plastic pieces ingested: 3.2) and flatfish (average number of plastic pieces ingested: 2.9) than by shrimp (average number of plastic pieces ingested: 1). More fish from the Clyde ingested plastic than similar Thames species (39% compared to 28% respectively); however, the average amount of plastic ingested did not differ between the sites.

Proteomic responses of European flounder to temperature and hypoxia as interacting stressors: Differential sensitivities of populations.

In the context of global change, ectotherms are increasingly impacted by abiotic perturbations. Along the distribution area of a species, the populations at low latitudes are particularly exposed to temperature increase and hypoxic events. In this study, we have compared the proteomic responses in the liver of European flounder populations, by using 2-D electrophoresis. One southern peripheral population from Portugal vs two northern core populations from France, were reared in a common garden experiment. Most of the proteomic differences were observed between the two experimental conditions, a cold vs a warm and hypoxic conditions. Consistent differentiations between populations were observed in accumulation of proteins involved in the bioenergetics- and methionine-metabolisms, fatty acids transport, and amino-acid catabolism. The specific regulation of crucial enzymes like ATP-synthase and G6PDH, in the liver of the southern population, could be related to a possible local adaptation. This southern peripheral population is spatially distant from northern core populations and has experienced dissimilar ecological conditions; thus it may contain genotypes that confer resilience to climate changes.

Changes in habitat of fish populations: An inverse problem.

Mathematical modelling applies to a wide variety of application areas, and is an active area of research in many disciplines. It is often the case that accurate depiction of real-world phenomena require increasingly complex models. Unfortunately, this increased complexity in a model causes great difficulty when seeking solutions. What is more, developing a model with known parameters that produces results consistent with observed behaviors may prove to be a difficult or even impossible task. These difficulties have brought about an interest in inverse problems. In this paper we utilize a collage-based approach to solve an inverse problem for a model for the migration of three fish species through floodplain waters. A derivation of the mathematical model is presented and a generalized collage method is discussed and applied to this model to recover diffusion parameters. Theoretical and numerical particulars are discussed and results are presented.

A Metabolomic Approach To Detect Effects of Salmon Farming on Wild Saithe (Pollachius virens) Populations.

A metabolomics approach was used to analyze effects of salmon farming on wild saithe (Pollachius virens) populations. Saithe fish were captured at two salmon farms and at two control locations around the island of Hitra, Norway. Changes in diet seem to drive changes in metabolic status of fishes. The liver and muscle tissues, from the fishes captured around the farm, showed higher levels of lactate and certain amino acids (glutamine, glutamate, and alanine) and lower levels of glucose and choline than the fishes captured in the control locations, far from the farm locations. The higher levels of lactate and amino acids could be related to the facility of obtaining food around the farm and the deficit in choline to the deficit of this nutrient in the salmon feed. At each location the fish were captured with either benthic gill nets and automatic jigging machines, and this feature showed also variations in different metabolites.

Population bottlenecks, genetic diversity and breeding ability of the three-spined stickleback (Gasterosteus aculeatus) from three polluted English Rivers.

Pollution is a significant environmental pressure on fish populations in both freshwater and marine environments. Populations subjected to chronic exposure to pollutants can experience impacts ranging from altered reproductive capacity to changes in population genetic structure. Few studies, however, have examined the reproductive vigor of individuals within populations inhabiting environments characterized by chronic pollution. In this study we undertook an analysis of populations of three-spined sticklebacks (Gasterosteus aculeatus) from polluted sites, to determine levels of genetic diversity, assess for evidence of historic population genetic bottlenecks and determine the reproductive competitiveness of males from these locations. The sites chosen included locations in the River Aire, the River Tees and the River Birket, English rivers that have been impacted by pollution from industrial and/or domestic effluents for over 100 years. Male reproductive competitiveness was determined via competitive breeding experiments with males and females derived from a clean water site, employing DNA microsatellites to determine parentage outcome. Populations of stickleback collected from the three historically polluted sites showed evidence of recent population bottlenecks, although only the River Aire population showed low genetic diversity. In contrast, fish collected from two relatively unpolluted sites within the River Gowy and Houghton Springs showed weak, or no evidence of such bottlenecks. Nevertheless, males derived from polluted sites were able to reproduce successfully in competition with males derived from clean water exposures, indicating that these bottlenecks have not resulted in any substantial loss of reproductive fitness in males.

Occurrence of B chromosomes in Cyphocharax modestus (Fernández-Yépez, 1948) and Steindachnerina insculpta (Fernández-Yépez, 1948)(Characiformes, Curimatidae) from the Tibagi River basin (Paraná State, Brazil)

We cytogenetically analyzed 18 individuals of Cyphocharax modestus, and 41 individuals of Steindachnerina insculpta from the Tibagi River basin (Paraná State, Brazil). All the specimens had 2n = 54 chromosomes, all meta-submetacentric (M-SM). The presence of 1 or 2 B chromosomes was seen in some individuals of C. modestus of the two sampled populations, showing inter- and intra individual variation. In S. insculpta, B chromosomes were also observed but only in one population, also showing inter- and intra individual variation. C-banding was used to show that the identified B chromosomes were totally heterochromatic in the two examined species.

Foram analisados, citogeneticamente, 18 indivíduos de Cyphocharax modestus e 41 indivíduos de Steindachnerina insculpta da bacia do rio Tibagi (Paraná, Brasil). Todos os espécimes apresentaram 2n = 54 cromossomos, todos do tipo meta-submetacêntrico (M-SM). A presença de 1 ou 2 cromossomos B foi detectada em alguns indivíduos de C. modestus de duas populações amostradas, evidenciando uma variação inter e intraindividual. Em S. insculpta, também foram observados cromossomos B, embora em somente uma população, mostrando também uma variação inter e intraindividual. Bandamento C foi usado para mostrar que os cromossomos B identificados apresentaram-se totalmente heterocromáticos nas duas espécies examinadas.

Occurrence of B chromosomes in Cyphocharax modestus (Fernández-Yépez, 1948) and Steindachnerina insculpta (Fernández-Yépez, 1948)(Characiformes, Curimatidae) from the Tibagi River basin (Paraná State, Brazil)

We cytogenetically analyzed 18 individuals of Cyphocharax modestus, and 41 individuals of Steindachnerina insculpta from the Tibagi River basin (Paraná State, Brazil). All the specimens had 2n = 54 chromosomes, all meta-submetacentric (M-SM). The presence of 1 or 2 B chromosomes was seen in some individuals of C. modestus of the two sampled populations, showing inter- and intra individual variation. In S. insculpta, B chromosomes were also observed but only in one population, also showing inter- and intra individual variation. C-banding was used to show that the identified B chromosomes were totally heterochromatic in the two examined species.

Foram analisados, citogeneticamente, 18 indivíduos de Cyphocharax modestus e 41 indivíduos de Steindachnerina insculpta da bacia do rio Tibagi (Paraná, Brasil). Todos os espécimes apresentaram 2n = 54 cromossomos, todos do tipo meta-submetacêntrico (M-SM). A presença de 1 ou 2 cromossomos B foi detectada em alguns indivíduos de C. modestus de duas populações amostradas, evidenciando uma variação inter e intraindividual. Em S. insculpta, também foram observados cromossomos B, embora em somente uma população, mostrando também uma variação inter e intraindividual. Bandamento C foi usado para mostrar que os cromossomos B identificados apresentaram-se totalmente heterocromáticos nas duas espécies examinadas.

Total-Hg and organic-Hg in Cephalopholis fulva (Linnaeus, 1758) from inshore and offshore waters of NE Brazil

To investigate whether source proximity or bioavailability is the major factor controlling both Hg concentration and Hg speciation in marine fishes, total- and organic-Hg content in muscle and liver tissues from different populations of Cephalopholis fulva (piraúna) from inshore and offshore waters of the Brazilian northeastern coast were analyzed. Average total-Hg in muscle (104 ng.g-1 w.w.) and liver (2,865 ng.g-1 w.w.) tissues, as well as organic-Hg concentrations in muscle (169 ng.g-1 w.w.) and liver (1,038 ng.g-1 w.w.), were much higher in the offshore population of C. fulva than in the inshore ones. In the inshore population total-Hg and organic-Hg average concentrations in muscle tissue were similar and reached only 49 ng.g-1 w.w., while in liver they reached 412 ng.g-1 w.w. for total-Hg and 180 ng.g-1 w.w., for organic-Hg. Concentrations of both Hg species in the two populations were higher in liver than in muscle. The average percentage contribution of organic-Hg to the total Hg content was higher in muscle (98-100 percent) than in liver (42-53 percent), but similar between the two populations. Total-Hg and organic-Hg concentrations in muscle and liver from the offshore population showed significant (P < 0.05) positive correlation with fish length. However, in the inshore population only the total-Hg and organic-Hg in muscle tissues correlate significantly with fish size. Although the coastal environments are enriched in total Hg relative to open waters, the significant higher Hg concentrations in the offshore population of C. fulva and the significant correlation found between organic-Hg in liver with fish size suggest higher bioavailability of Hg in offshore waters relative to inshore ones.

As concentrações de Hg-total e Hg-orgânico foram determinadas em diferentes populações de Cephalopholis fulva (piraúna) capturadas em águas costeiras e em bancos oceânicos do litoral nordeste do Brasil. A comparação entre as duas populações permitiu investigar o efeito da proximidade de fontes sobre as concentrações, e a especiação de Hg em músculo e fígado desta espécie. As concentrações médias de Hg-total em músculo (104 ng.g-1 w.w.) e fígado (2,865 ng.g-1 w.w.), assim como as concentrações de Hg-orgânico em músculo (169 ng.g-1 w.w.) e fígado (1,038 ng.g¹ w.w.) foram muito maiores na população capturada nos bancos oceânicos do que na população costeira. Nesta, as concentrações médias de Hg-total e Hg-orgânico na musculatura de C. fulva foram similares e baixas (49 ng.g-1 w.w.), enquanto que atingiram 412 ng.g-1 w.w. de Hg-total e 180 ng.g-1 w.w. de Hg-orgânico no fígado destes animais. As concentrações das duas espécies de Hg foram significativamente maiores no fígado do que na musculatura. A contribuição percentual média de Hg-orgânico para a concentração total de Hg nos peixes foi maior para músculo (98-100 por cento) que para fígado (42-53 por cento), mas semelhante entre as duas populações. As concentrações de Hg-total e Hg-orgânico na musculatura e no fígado de C. fulva mostraram-se positivamente correlacionadas com o tamanho do animal (P < 0,05). Entretanto, na população costeira somente as concentrações destas espécies de Hg na musculatura apresentaram correlações significativas com o tamanho do animal. Embora o ambiente costeiro seja relativamente enriquecido em Hg, em relação aos bancos oceânicos, as maiores concentrações de Hg foram verificadas na população oceânica de C. fulva. A correlação significativa entre Hg-orgânico no fígado e tamanho do animal no fígado sugerem uma maior biodisponibilidade do Hg em águas oceânicas quando comparada às águas costeiras.