Numerical models of ecological systems are increasingly used to address complex environmental and resource management questions. One challenge for scientists, managers, and stakeholders is to appraise how well suited these models are to answer questions of scientific or societal relevance, that is, to perform, communicate, or access transparent evaluations of ecological models. While there have been substantial developments to support standardised descriptions of ecological models, less has been done to standardise and to report model evaluation practices. We present here a general protocol designed to guide the reporting of model evaluation. The protocol is organised in three major parts: the objective(s) of the modelling application, the ecological patterns of relevance and the evaluation methodology proper, and is termed the OPE (objectives, patterns, evaluation) protocol. We present the 25 questions of the OPE protocol which address the many aspects of the evaluation process and then apply them to six case studies based on a diversity of ecological models. In addition to standardising and increasing the transparency of the model evaluation process, we find that going through the OPE protocol helps modellers to think more deeply about the evaluation of their models. From this last point, we suggest that it would be highly beneficial for modellers to consider the OPE early in the modelling process, in addition to using it as a reporting tool and as a reviewing tool.
Harvesting is typically size-selective, targeting large individuals. This is expected to lead to reduced average body size and earlier maturation (i.e. faster life histories). Such changes can also affect traits seemingly unrelated to harvesting, including immunocompetence. Here we test four hypotheses on how harvesting affects immunocompetence based on the pace-of-life syndrome, habitat area limitation and energy allocation and acquisition, respectively. We empirically evaluate these hypotheses using an experimental system consisting of the ectoparasite Gyrodactylus turnbulli and lines of guppies Poecilia reticulata that had been subjected to either small, random or large size-selective harvest for over 12 years. We followed the infection progression of individually infected fish for 15 days. We found significant differences between the harvested lines: fish from the small-harvested lines had the highest parasite loads. During the early phase of the infection, parasite loads were the lowest in the large-harvested lines, whereas the terminal loads were the lowest for the random-harvested lines. These results agree with the predictions from the energetic trade-off and surface area hypotheses. To our knowledge, this is the first demonstration of the consequences of size-selective harvesting on immunocompetence.
Fish populations may spawn a vast number of offspring, while only a small and highly variable fraction of a new cohort survives long enough to enter into the fisheries as recruits. It is intuitive that the size and state of the spawning stock, the adult part of the fish population, is important for recruitment. Additionally, environmental conditions can greatly influence survival through vulnerable early life stages until recruitment. To understand what regulates recruitment, an essential part of fish population dynamics, it is thus necessary to explain the impact of fluctuations in both spawning stock and environment, including interactions. Here, we examine if the connection between the environment and recruitment is affected by the state of the spawning stock, including biomass, mean age and age diversity. Specifically, we re‐evaluate the hypothesis stating that recruitment from a spawning stock dominated by young fish and few age classes is more vulnerable to environmental fluctuations. We expand upon earlier work on the Barents Sea stock of Atlantic cod, now with data series extended in time both backwards and forwards to cover the period 1922–2019. While our findings are correlative and cannot prove a specific cause and effect mechanism, they support earlier work and strengthen the evidence for the hypothesis above. Furthermore, this study supports that advice to fisheries management should include considerations of environmental status.
The precise homing of Atlantic salmon to their natal river and spawning grounds is the foundation for locally adapted genetically differentiated populations across rivers or across river sections. A sequential imprinting hypothesis states that salmon smolts may imprint on environmental clues along the outward migration route and then use this in reverse order to direct the spawning migration later in life. In this study, we provide empirical support for this hypothesis. PIT-tagged wild Atlantic salmon using a 2 km hydropower tunnel as downstream migrating smolts had a 18% (1SW) and 23% (2SW) lower probability of successfully migrating through the parallel river stretch as adult spawners compared to spawners that migrated through the same river stretch as smolts. These findings highlight how a fine-scale riverine migration route may be imprinted in wild Atlantic salmon smolts. From an applied perspective, these results stress the importance of not depriving smolts from parts of their migration route to ensure successful return of adults to their natal spawning grounds.
Parasite biodiversity in cetaceans represents a neglected component of the marine ecosystem. This study aimed to investigate the distribution and genetic diversity of anisakid nematodes of the genus Anisakis sampled in cetaceans from the Northeast Atlantic Ocean and the Mediterranean Sea. A total of 478 adults and pre-adults of Anisakis spp. was identified by a multilocus genetic approach (mtDNA cox 2 , EF1 α − 1 nDNA and nas 10 nDNA gene loci) from 11 cetacean species. A clear pattern of host preference was observed for Anisakis spp. at cetacean family level: A. simplex (s.s.) and A. pegreffii infected mainly delphinids; A. physeteris and A. brevispiculata were present only in physeterids, and A. ziphidarum occurred in ziphiids. The role of cetacean host populations from different waters in shaping the population genetic structure of A. simplex (s.s.), A. pegreffii and A. physeteris was investigated for the first time. Significant genetic sub-structuring was found in A. simplex (s.s.) populations of the Norwegian Sea and the North Sea compared to those of the Iberian Atlantic, as well as in A. pegreffii populations of the Adriatic and the Tyrrhenian Seas compared to those of the Iberian Atlantic waters. Substantial genetic homogeneity was detected in the Mediterranean Sea population of A. physeteris. This study highlights a strong preference by some Anisakis spp. for certain cetacean species or families. Information about anisakid biodiversity in their cetacean definitive hosts, which are apex predators of marine ecosystems, acquires particular importance for conservation measures in the context of global climate change phenomena.
Distribution of Earth’s biomes is structured by the match between climate and plant traits, which in turn shape associated communities and ecosystem processes and services. However, that climate–trait match can be disrupted by historical events, with lasting ecosystem impacts. As Earth’s environment changes faster than at any time in human history, critical questions are whether and how organismal traits and ecosystems can adjust to altered conditions. We quantified the relative importance of current environmental forcing versus evolutionary history in shaping the growth form (stature and biomass) and associated community of eelgrass ( Zostera marina ), a widespread foundation plant of marine ecosystems along Northern Hemisphere coastlines, which experienced major shifts in distribution and genetic composition during the Pleistocene. We found that eelgrass stature and biomass retain a legacy of the Pleistocene colonization of the Atlantic from the ancestral Pacific range and of more recent within-basin bottlenecks and genetic differentiation. This evolutionary legacy in turn influences the biomass of associated algae and invertebrates that fuel coastal food webs, with effects comparable to or stronger than effects of current environmental forcing. Such historical lags in phenotypic acclimatization may constrain ecosystem adjustments to rapid anthropogenic climate change, thus altering predictions about the future functioning of ecosystems.
We studied molecular effects (RNAseq and qPCR) of first feeding prey types (copepods or rotifers/ Artemia ) on skeletal muscle myogenesis and growth dynamics (proliferation, differentiation), metabolism (glycolysis, gluconeogenesis, oxidative phosphorylation), and antioxidant defense system (production/regulation of reactive oxygen species (ROS) in cod ( Gadus morhua ) larval skeletal muscle. Larval somatic growth rates were significantly higher in copepod fed larvae, although shifts in gene expressions related to muscle growth dynamics between hypertrophy and hyperplasia and generation and regulation of ROS mostly occurred around 5-, 10-, and 15-mm standard length (SL) for both groups. Gene expression for cell membrane proteins (such as nox1 and igf1r ) peaked at 7 mm SL in all larvae, corresponding with increased ROS expressions in cod muscle during the exponential stratified hyperplasia phase from 7 mm SL. Expression for muscle differentiation ( mef2a ) occurred continuously (strongest from 10 mm SL). Expressions for muscle proliferation ( pcna ) and hydrogen peroxide (H 2 O 2 ) generation ( sod1 and sod2 ) occurred in the 5 - 15 mm SL range, peaking at 10 mm SL in all larvae. A downregulation of sod1 and sod2 in skeletal muscle from 15 mm SL indicated the first response of the defense antioxidant system. Gene expressions related to glucose metabolism ( slc2A11 , pfk , fpb2 , ldha ) was 3 - 10 times higher in copepod-fed larvae than in rotifer/ Artemia -fed larvae between 7 – 10 mm (live prey period). Copepods move faster than rotifers, and cod larvae will also gradually increase their active swimming periods, due to less viscous forces. Active swimming during the strongest muscle stratified hyperplasia phase (7 – 10 mm SL) could promote a better delivery and transport across the muscle membrane and intracellular flux through glycolysis and oxidative phosphorylation and would contribute to the observed earlier and more effective glucose metabolism in the larvae fed copepods. We suggest that active swimming is an important factor promoting cod larval muscle growth, especially during the strongest muscle hyperplasia phase between 7 and 10 mm SL. The rapid movements of copepods and better nutritional composition could play important roles in stabilizing ROS levels, promoting high swimming activities and enhancing long-term muscle growth in cod.
Net primary productivity (NPP) plays a pivotal role in the global carbon balance but estimating the NPP of underwater habitats remains a challenging task. Seaweeds (marine macroalgae) form the largest and most productive underwater vegetated habitat on Earth. Yet, little is known about the distribution of their NPP at large spatial scales, despite more than 70 years of local-scale studies being scattered throughout the literature. We present a global dataset containing NPP records for 246 seaweed taxa at 429 individual sites distributed on all continents from the intertidal to 55 m depth. All records are standardized to annual aerial carbon production (g C m ⁻² yr ⁻¹ ) and are accompanied by detailed taxonomic and methodological information. The dataset presented here provides a basis for local, regional and global comparative studies of the NPP of underwater vegetation and is pivotal for achieving a better understanding of the role seaweeds play in the global coastal carbon cycle.
Cycling of organic carbon in the ocean has the potential to mitigate or exacerbate global climate change, but major questions remain about the environmental controls on organic carbon flux in the coastal zone. Here, we used a field experiment distributed across 28° of latitude, and the entire range of 2 dominant kelp species in the northern hemisphere, to measure decomposition rates of kelp detritus on the seafloor in relation to local environmental factors. Detritus decomposition in both species were strongly related to ocean temperature and initial carbon content, with higher rates of biomass loss at lower latitudes with warmer temperatures. Our experiment showed slow overall decomposition and turnover of kelp detritus and modeling of coastal residence times at our study sites revealed that a significant portion of this production can remain intact long enough to reach deep marine sinks. The results suggest that decomposition of these kelp species could accelerate with ocean warming and that low-latitude kelp forests could experience the greatest increase in remineralization with a 9% to 42% reduced potential for transport to long-term ocean sinks under short-term (RCP4.5) and long-term (RCP8.5) warming scenarios. However, slow decomposition at high latitudes, where kelp abundance is predicted to expand, indicates potential for increasing kelp-carbon sinks in cooler (northern) regions. Our findings reveal an important latitudinal gradient in coastal ecosystem function that provides an improved capacity to predict the implications of ocean warming on carbon cycling. Broad-scale patterns in organic carbon decomposition revealed here can be used to identify hotspots of carbon sequestration potential and resolve relationships between carbon cycling processes and ocean climate at a global scale.
The European Fish Ageing Network (EFAN) funded by the European Union, is reviewed, and assessed after a 20-year hiatus. The large number of scientists and technicians involved in this independent and informal network, and the time invested (four years), provided a significant advance in fish age estimation and methodologies. The results presented are based on two survey questionnaires sent to EFAN members, specifically to those who had been most actively involved in the programme. Overall, EFAN can be considered as successful as it fulfilled the aim of the FAIR (Fostering Awareness Inclusion and Recognition) program in improving collaboration both at a national and European levels in the field of sclerochronology. Adding to the success was that many survey participants reported a positive impact on both their creativity and scientific careers, particularly participants from university environments and the female members, and around 50% of the participants continued in their age-related research careers. These factors, as well as the positive scientific impact EFAN has had in various European countries (n = 16), point to a very successful programme. The aim of improving what is an objective approach required to interpret growth increments in calcified structures (otoliths) in fishes, is reflected in the various tools developed by EFAN, all of which are found in the many reports produced by the Network. Examples are seen in the quality control approach by the International Council for the Exploration of the Sea (ICES), where tools developed by EFAN have been key to their fisheries management approach. Our general impression is that a project with a lifetime of around four years in principle provides a suitable time period to develop age estimation tools, quality control routines, and working procedures to improve the use of fish age data for fish stock assessments. We argue however, that developing a functioning network requires more time than a conventional project. Therefore, to fully meet the aims of projects such as EFAN, a period of between 10 and 15 years is a more appropriate time frame for these types of programmes to run. A longer time scale can help ensure recommendations are regularly followed, can provide more confidence in on-going routine age estimation data, and so achieve a significant improvement in the application of ageing methods. In turn a more accurate and robust scientific outcome would be available for European fish stock assessments.
Kudoa thyrsites is a myxosporean parasite (Cnidaria, Myxozoa) that infects the skeletal and cardiac muscle of Northeast Atlantic (NEA) mackerel ( Scomber scombrus ). Heavy infections are associated with post-mortem myoliquefaction of the host skeletal muscle which reduces the quality of the fish product. The biological infection characteristics of the parasite in NEA mackerel are poorly known. This study examined the distribution of K. thyrsites in various organs of NEA mackerel from the northern North Sea, and elucidates the relationship between density of infection, developmental stage and parasite distribution in the musculature, and the extent of visible flesh myoliquefaction. Quantitative polymerase chain reaction (qPCR) data showed that K. thyrsites is unevenly distributed in the somatic musculature of the fish host, with highest density in the anterior ventral muscle sections—the belly flaps. A weak positive correlation was observed between the level of myoliquefaction and the parasite density in the fish host muscle. This relationship was also reflected by the amount and distribution of parasite developmental stages seen during histological examinations. Histological findings indicate an association between the dispersion of free myxospores and the level of myoliquefaction of the fish host muscle. Visceral organs were also found infected using qPCR, although at lower densities compared to the musculature.
Inclusion of new environmental toxicants increase with the amount of plant ingredients substituting marine proteins and oils in feed for farmed Atlantic salmon (Salma salar). Agricultural pesticides like chlorpyrifos-methyl, present in commercial salmon feeds, may affect salmon immune and detoxification responses. Atlantic cod (Gadus morhua), surrounding the net pens, grazing on feces and uneaten pellets may be affected accordingly. The aim of this study was to analyze transcription responses in Atlantic cod head kidney tissue and isolated leukocytes following dietary chlorpyrifos-methyl inclusions and possible interactions with proinflammatory signals. Head kidney tissues and leukocytes were isolated from cod fed diets contaminated with chlorpyrifos-methyl (0.5 mg/kg, 2.4 mg/kg, 23.2 mg/kg) for 30 days. The isolated leukocytes were further challenged with bacteria (lipopolysaccharide (LPS), virus (polyinosinic acid:polycytidylic acid (PIC) mimic and l-arginine, an immuno-modulating amino acid, in vitro. The LPS-induced transcription of the interleukin genes il-1β, il-6, il-8 increased in leukocytes isolated from cod fed chlorpyrifos-methyl 23.2 mg/kg, compared to cod fed the control diet, indicating increased inflammation. Transcriptional levels of carnitine palmitoyl transferase (cpt1a), aryl hydrogen receptor (ahr) and catalase (cat) were all reduced by dietary inclusions of chlorpyrifos-methyl in the leukocytes. The findings suggests that dietary chlorpyrifos-methyl exposure impair inflammation, detoxification and redox signaling in cod leukocytes.
We examine an Arctic winter storm event, which led to ice break–up, the formation of open leads, and the subsequent freezing of these leads. The methane (CH4) concentration in under–ice surface water before and during the storm event was 8–12 nmol L⁻¹, which resulted in a potential sea–to–air CH4 flux ranging from +0.2 to +2.1 mg CH4 m⁻² d⁻¹ in open leads. CH4 ventilation between seawater and atmosphere occurred when both open water fraction and wind speed increased. Over the nine days after the storm, sea ice grew 27 cm thick. Initially, CH4 concentrations in the sea ice brine were above the equilibrium with the atmosphere. As the ice grew thicker, most of the CH4 was lost from upper layers of sea ice into the atmosphere, implying continued CH4 evasion after the leads were ice–covered. This suggests that wintertime CH4 emissions need to be better constrained.
Automation of feeding control for sea-caged Atlantic salmon is important to reduce waste feed. Hydroacoustic appetite-led feeding, or echofeeding, uses echo sound to monitor fish biomass in a defined feeding area. As the fish become satiated and begin to leave the feeding area, the monitored biomass falls, enabling the setting of threshold levels of biomass at depth. Software then decides to continue or stop feeding. Here, we implemented a fully autonomous echofeeding system in 3 sea cages with salmon during summer (900 g, ~14 °C) and winter (5300 g, ~5 °C). To find the best signal of feeding activity, fish biomass was monitored with two echo sounder transducers at different depths and echo beam widths, directed upwards towards the feeding area. Prior to echofeeding, we trained salmon to consume their daily ration in short, intense feeding bouts. The fish adapted to consume their daily food ration in just 1 h and sustained their feeding activity close to the surface under the echofeeding regime. The feeding response was positively correlated with feeding intensity and was strongest at the surface (0–1.5 m), with a narrow echo beam from 8 m depth giving the best proxy of fish appetite. Appetite varied between meals and days, yet echofeeding prevented waste feed while fish maintained strong growth rates. Echofeeding is simple to deploy, as farmed salmon, independent of fish size or season, can adapt to changes in feeding regimes. Both feeding intensity and the biomass threshold for feeding cessation were kept static under echofeeding, which challenge the industry's standard manual feeding control practice where feeding intensity is adjusted by visually assessing appetite within meals. Our results provide novel insight into basic principles of hydroacoustic-based feeding and autonomous feeding control in general and highlight echofeeding as a promising technology.
Like many animals, northern temperate eel can enter a hibernation-like state and become dormant during the winter. Knowledge of overwintering behaviour in eel is sparse and mainly based on anecdotal observations and a few experimental studies on thermal tolerance. We studied European eel (Anguilla anguilla) overwintering behaviour in a Skagerrak fjord in Southern Norway, during three consecutive years, using an array of acoustic receivers and acoustic tags with depth and temperature sensors. We obtained results from 55 yellow eel, of which 19 were studied for one winter, 35 for two winters and one for three winters. Dormancy was inferred to begin in September for the earliest individuals and lasted until May for the last, with the majority of eel dormant from at least late October–November until mid-April. The timing of dormancy was mainly related to photoperiod and less to temperature. More than 50% of eel became dormant when day length was <9 hours and became active when day length was >14 hours. Approximately 10% of eel remained active during the winter and 31% of eel changed their pattern between consecutive years. Some dormant individuals exhibited activity periods that interrupted their dormancy. Eel in the outer fjord nearer the open sea became dormant before eel in the inner more freshwater part of the fjord, and were dormant longer.
Aquaculture operations are currently the fastest-growing food production industry, increasing output over 20 times in the past few decades alone. Waste production on “fed” aquaculture farms, like Atlantic Salmon, is an issue for management and public perception. Integrated Multi-Trophic Aquaculture (IMTA) is the co-cultivation of species from different trophic levels on an aquaculture farm; from a theoretical perspective, the metabolic waste and uneaten feed from the top-level species like Atlantic Salmon is used by lower-level trophic species like shellfish and macroalgae, minimizing the potential impact of these wastes on the ecosystem. Despite the theoretical benefits, IMTA is currently not applied as a mitigation measure in Atlantic Salmon farms. The main goal of this research was to determine the current state-of-the-art of IMTA and its potential to be effectively implemented on Atlantic Salmon aquaculture farms in a commercially viable manner. This study explored and investigated current methods, applications, uses, and mitigation efficiency of IMTA to address challenges on salmon farms through an in-depth PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) method literature review. Additionally, industry experts were surveyed to understand industry perspectives on IMTA effectiveness and the potential for use. Though surveyed industry members identified mitigation as a moderately viable benefit, the current literature indicates challenges related to scaling up the culture of extractive species to reach a meaningful mitigation level. Economic issues regarding capital and maintenance costs constitute bottlenecks for implementation. The lack of governmental support and commitment to implementation and innovation were repeatedly referenced among the literature review papers and the industry survey. Despite speculations on its viability, the fact that IMTA is not commonly implemented at the commercial scale constitutes a barrier for industry adoption. The next steps for IMTA could be related to the development of demonstration sites at the commercial level to showcase actual viability from a financial and managerial, economic, and environmental standpoint.
Coastal areas are important habitats for early life stages of many fish species. These habitats are used as nursery grounds and can provide a significant contribution to the recruitment of a fish population. In 1919, standardized sampling with a beach seine along the Norwegian Skagerrak coastline was established mainly to target 0-group fish. Here, we focus on Atlantic herring and European sprat to explore whether inter-annual variability in the abundance of these species is indicative of variability in recruitment. We investigated if the abundance of 0-group herring and sprat are affected by environmental factors. Further, the beach seine abundance indices were compared with recruitment estimates of neighboring stocks. There was a clear correlation between herring and sprat abundance in the beach seine samples. While sprat abundance was mainly affected by environmental factors such as temperature and current drift, herring abundance was positively affected by the recruitment of the neighboring stock of western Baltic spring spawners. One plausible explanation could be that sprat recruit to a more local component, while herring of the neighboring stock utilize the Skagerrak coastline as nursery grounds. This study demonstrates the importance of long time series and can provide new insight into the dynamics and structure of multiple fish species.
Recent adaptive radiations are models for investigating mechanisms contributing to the evolution of biodiversity. An unresolved question is the relative importance of new mutations, ancestral variants, and introgressive hybridization for phenotypic evolution and speciation. Here, we address this issue using Darwin’s finches and investigate the genomic architecture underlying their phenotypic diversity. Admixture mapping for beak and body size in the small, medium, and large ground finches revealed 28 loci showing strong genetic differentiation. These loci represent ancestral haplotype blocks with origins predating speciation events during the Darwin’s finch radiation. Genes expressed in the developing beak are overrepresented in these genomic regions. Ancestral haplotypes constitute genetic modules for selection and act as key determinants of the unusual phenotypic diversity of Darwin’s finches. Such ancestral haplotype blocks can be critical for how species adapt to environmental variability and change.
Few studies have been published on occurrence and distribution on microplastics (MPs) in invertebrates from the Arctic. We still need to develop harmonised methods to enable good comparison between studies taking into account recovery rates, size ranges, shapes and polymer types. Here, we review studies on MPs in invertebrates from the Arctic and present suggestions on sampling protocols and potential indicator species. Since information on MPs in Arctic invertebrates is vastly lacking, we recommend to at least include suspension feeding bivalves like mussels in monitoring programmes to function as indicator species in the Arctic. Mussels have also been suggested as indicator species for MP monitoring in coastal regions further south. Although we recognise the challenge with particle selection and egestion in mussels as well as the relatively low concentrations of MPs in Arctic waters, uptake levels seem to represent recent exposures. More research is needed to understand these selection processes and how they affect the bioaccumulation processes. Future research should include studies on whether different functional groups of invertebrates have different exposures to MPs, e.g., if there are differences between sessile versus motile species or different feeding strategies. More knowledge on monitoring strategies for pelagic and benthic species is needed.
The pollution of the environment with plastics is of growing concern worldwide, including the Arctic region. While larger plastic pieces are a visible pollution issue, smaller microplastics are not visible with the naked eye. These particles are available for interaction by Arctic biota and have become a concern for animal and human health. The determination of microplastic properties includes several methodological steps, i.e. sampling, extraction, quantification and chemical identification. This review discusses suitable analytical tools for the identification, quantification and characterization of microplastics in the context of monitoring in the Arctic. It further addresses quality assurance and quality control (QA/QC) which is particularly important for the determination of microplastic in the Arctic, as both contamination and analyte losses can occur. It presents specific QA/QC measures for sampling procedures and for the handling of samples in the laboratory, either on land or on ship, and considering the small size of microplastics as well as the high risk of contamination. The review depicts which data should be mandatory to report, thereby supporting a framework for harmonized data reporting.
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