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Continental shelves experience many human pressures with demersal fisheries central to disturbing the ocean floor. However, ecological processes such as predation rates of benthos and their relationship with bottom fishing are often unknown for large marine ecosystems. We examined the amount of benthos consumed by 14 benthivorous fishes, the overlap between benthos predation and bottom fishing (dredge and trawl gear), and temporal trends in benthivorous fish abundance and the number of fishing trips on the northeast US continental shelf. Mean annual predation (biomass of prey removed) and 95% confidence intervals ranged from.0002 (.0001–.0003) to 3967 (1761–7112) t per 10‐min area squared grid cell and prey taxa for these benthivorous fishes. Predation and bottom fishing had overlapping footprints of activity, which were slightly stronger for dredge gear. Trophic success (ratio of prey biomass eaten to the biomass of the benthivore community per grid cell) revealed more Bivalvia, Gammaridea, and Polychaeta eaten in areas targeted by trawling with more fish biomass. In contrast, dredging did not target fish biomass, but these areas had increased (Echinoidea, Gammaridea, and other benthos) or decreased (Ophiuroidea) trophic success relative to dredging footprint, suggesting habitat preferences for benthic prey and demersal fisheries have converged rather than diverged. Despite declines in bottom fishing, recent increases in benthivorous fish abundance and growing interest in ocean floor use suggest that fisheries managers should ensure benthivores have sufficient prey resources relative to their community size and human pressures to promote long‐term sustainability of demersal fisheries and healthy ecosystems. [ABSTRACT FROM AUTHOR]

Gulf Stream flounder, Citharichthys arctifrons, are regularly observed in fish diets of the northeast U.S. continental shelf, yet lack commercial value and are often ignored. Similarly, Gulf Stream flounder diets of the Northwest Atlantic have remained largely unexamined, except for a brief period from 1976 to 1980. To better understand their role in the ecosystem, juvenile through adult Gulf Stream flounder were examined both as a predator and prey, and the magnitude of their feeding footprint (removal of prey biomass) was quantified for the northeast U.S. continental shelf. Their stomachs were sampled from 2005 to 2010, with the majority examined in the field macroscopically. Due to large proportions of unidentifiable prey, the effort was expanded in 2011–2012, and all stomachs were processed in the laboratory microscopically. Gulf Stream flounder were consumed by 15 fish, and what they eat (percentage mass and percentage frequency of occurrence) was documented by season, spatial region and year. Highly benthivorous, Gammaridea and Polychaeta dominated the diet in all years, seasons and regions, but Ophiuroidea (brittle stars) were also prominent in Southern New England during the spring. Gulf Stream flounder diets remained consistent across regions and time, with only a few feeding differences between seasons and one region. Relative to the productivity of benthos for this shelf ecosystem, the feeding footprint of Gulf Stream flounder was minor for their predominant benthic prey with a maximum percentage of benthos production eaten of 0.01% m−2 in Southern New England. With an ecosystem perspective, this feeding information offers a foundation for improving fisheries management among shared living marine resources considering benthic habitat and prey availability. [ABSTRACT FROM AUTHOR]

Declining physiological status in marine top consumers has been observed worldwide. We investigate changes in the physiological status and population/community traits of six consumer species/groups in the Baltic Sea (1993–2014), spanning four trophic levels and using metrics currently operational or proposed as indicators of food-web status. We ask whether the physiological status of consumers can be explained by food-web structure and prey food value. This was tested using partial least square regressions with status metrics for gray seal, cod, herring, sprat and the benthic predatory isopod Saduria as response variables, and abundance and food value of their prey, abundance of competitors and predators as predictors. We find evidence that the physiological status of cod, herring and sprat is influenced by competition, predation, and prey availability; herring and sprat status also by prey size. Our study highlights the need for management approaches that account for species interactions across multiple trophic levels. [ABSTRACT FROM AUTHOR]

The foraging activity of large-bodied benthivorous fish has been suggested to be of key importance for maintaining shallow lakes in a turbid state. Since especially the spring ecosystem dynamics determines the successive state of shallow lakes, such impact could depend on seasonality in benthivore activity patterns. However, we do not yet know to what extent the activity of large-bodied benthivorous fish affects lake turbidity across the year. In order to investigate seasonal dynamics in bream activity and its impact on water turbidity under natural conditions, bream daily activity was studied in a small (39 ha) shallow Danish lake using passive biotelemetry technology, i.e. a modified Passive Integrated Transponder (PIT)-tag antenna system. We tracked the activity of 448 benthivorous bream over a period of four years (2012 to 2016) and during the same period wind conditions, water turbidity and temperature was measured. Results showed a clear relationship between bream activity and water turbidity at water temperature below 15°C indicating that winter season activity of benthivorous bream may play an important role for maintaining lake ecosystems in a turbid state. Also wind speed and wind direction affected water turbidity, suggesting that wind induced resuspension can be important even in small shallow lakes. This is to our knowledge the first full-scale study under natural conditions to describe how bream activity influence lake turbidity on a day-to-day basis. Our findings also add a seasonal component to previous findings by showing that benthivorous feeding bream have the potential to increase water turbidity also in the winter season and thereby, ultimately, impact ecosystem functioning within shallow lakes.

The recent focus on a common movement ecology paradigm has increased awareness about the importance of distinguishing different movement patterns for understanding their specific impact on animal ecology and evolution. One specific form of movement is nomadism, where animals move between habitats in an arrhythmic fashion. Although not yet described in detail for freshwater fish, nomadism between lakes within drainage systems could affect local lake food webs in an otherwise unpredictable fashion. In this study, we used passive telemetry to describe inter‐lake movements of 1,280 individually tagged adult benthivorous bream (Abramis brama) over nine contiguous years in a drainage system with two paired lakes. The movements can best be described as partial nomadism, where a part of the population is neither resident nor migratory, but instead moves between lakes in a variable, arrhythmic fashion, often with long residency in one lake before moving to the other. We found extensive between‐year variation in the proportion and direction of bream moving, with higher movement propensity being partly associated with lower somatic condition. Notably, movements out of lakes were significantly more in direction of the neighbouring lake than away from the paired lakes, suggesting that at least direction was not random. Since bream are important ecosystem engineers, fluctuating densities of adult bream could affect ecological stability in lakes. Our study suggests that fish populations in interconnected lakes within drainages should not be treated as isolated units, and we discuss this in relation to lake ecology and the importance for lake ecosystem management. [ABSTRACT FROM AUTHOR]

The foraging activity of large-bodied benthivorous fish has been suggested to be of key importance for maintaining shallow lakes in a turbid state. since especially the spring ecosystem dynamics determines the successive state of shallow lakes, such impact could depend on seasonality in benthivore activity patterns. However, we do not yet know to what extent the activity of large-bodied benthivorous fish affects lake turbidity across the year. In order to investigate seasonal dynamics in bream activity and its impact on water turbidity under natural conditions, bream daily activity was studied in a small (39 ha) shallow Danish lake using passive biotelemetry technology, i.e. a modified Passive Integrated Transponder (PIT)-tag antenna system. We tracked the activity of 448 benthivorous bream over a period of four years (2012 to 2016) and during the same period wind conditions, water turbidity and temperature was measured. Results showed a clear relationship between bream activity and water turbidity at water temperature below 15°C indicating that winter season activity of benthivorous bream may play an important role for maintaining lake ecosystems in a turbid state. Also wind speed and wind direction affected water turbidity, suggesting that wind induced resuspension can be important even in small shallow lakes. This is to our knowledge the first full-scale study under natural conditions to describe how bream activity influence lake turbidity on a day-to-day basis. our findings also add a seasonal component to previous findings by showing that benthivorous feeding bream have the potential to increase water turbidity also in the winter season and thereby, ultimately, impact ecosystem functioning within shallow lakes. [ABSTRACT FROM AUTHOR]

Background: In recent decades, many attempts have been made to restore eutrophic lakes through biomanipulation. Reducing the populations of planktivorous and benthivorous fish (either directly or through stocking of piscivorous fish) may induce ecosystem changes that increase water transparency and decrease the risk of algal blooms and fish kills, at least in the short term. However, the generality of biomanipulation effects on water quality across lake types and geographical regions is not known. Therefore, we have undertaken a systematic review of such effects in eutrophic lakes in temperate regions throughout the world. Methods: Searches for literature were made using online publication databases, search engines, specialist websites and bibliographies of literature reviews. Search terms were developed in English, Danish, Dutch and Swedish. Identified articles were screened for relevance using inclusion criteria set out in an a priori protocol. To reduce the risk of bias, we then critically appraised the combined evidence found on each biomanipulation. Data were extracted on outcomes such as Secchi depth and chlorophyll a concentration before, during and/or after manipulation, and on effect modifiers such as lake properties and amounts of fish removed or stocked. Results: Our searches identified more than 14,500 articles. After screening for relevance, 233 of them remained. After exclusions based on critical appraisal, our evidence base included useful data on 128 biomanipulations in 123 lakes. Of these interventions, 85% had been made in Europe and 15% in North America. Meta-analysis showed that removal of planktivores and benthivores (with or without piscivore stocking) leads to increased Secchi depth and decreased chlorophyll a concentration during intervention and the first three years afterwards. Piscivore stocking alone has no significant effect. The response of chlorophyll a levels to biomanipulation is stronger in lakes where fish removal is intense, and in lakes which are small and/or have high pre-manipulation concentrations of total phosphorus. Conclusions: Our review improves on previous reviews of biomanipulation in that we identified a large number of case studies from many parts of the world and used a consistent, repeatable process to screen them for relevance and susceptibility to bias. Our results indicate that removal of planktivorous and benthivorous fish is a useful means of improving water quality in eutrophic lakes. Biomanipulation tends to be particularly successful in relatively small lakes with short retention times and high phosphorus levels. More thorough fish removal increases the efficacy of biomanipulation. Nonetheless successes and failures have occurred across a wide range of conditions. [ABSTRACT FROM AUTHOR]

Benthivorous fish in shallow, aquatic systems have been correlated with increased turbidity and declines in macrophyte production and wildlife use. Bullheads have been credited with increasing turbidity, but this has been seldom tested and has not been studied in a diked marsh. To assess the relationships of black bullhead (Ameiurus melas) and turbidity, we assembled mesocosms in the Show Pool Management Unit of The Ottawa National Wildlife Refuge, OH, U.S.A. We stocked treatment enclosures with different biomasses of black bullhead at weekly intervals. Mean turbidity within treatment enclosures was significantly higher than within controls but remained lower than that of the open marsh. Both surface and bottom turbidity increased with adult and juvenile black bullhead biomass. Turbidity increased with fine sand concentration only in the presence of juvenile fish. Wind speed and direction were significant influences on the turbidity of the open marsh, but not within control enclosures. That treatment turbidity – even at extreme biomasses – remained significantly lower than the turbidity of the open marsh implicates fetch in having a greater influence on a marsh's turbidity than the presence of black bullhead. The greater impact of benthivorous fish on turbidity within shallow systems may be an indirect one through the destruction of macrophytes and subsequent destabilization of unconsolidated substrates. [ABSTRACT FROM AUTHOR]

Overlapping territories of a benthophagous morwong, Goniistius zonatus, were studied at two temperate water locations (Morode and Arakashi) in southern Japan. At both locations, total length (TL) of the fish inhabiting the study areas ranged from 12 cm to 34 cm, but fish 20–25 cm TL were not found in the Arakashi study area. At Morode, individuals maintained territories against conspecifics of similar size, and the territories broadly overlapped among three size classes (small < 20 cm ≤ medium <25 cm ≤ large). At Arakashi, large-sized fish chased individuals of both the same- and medium-sized individuals from their territories, resulting in territory overlap only between large and small size classes. The territories were apparently maintained for feeding, as the main activity of the fish within the territories was foraging and no reproductive behavior was observed at either location. All fish foraged on similar substrates in the daytime. At Morode, however, the diet composition differed among different size classes, whereas at Arakashi, fish of all sizes fed on quite similar foods. A comparison between the two populations indicates that the territory overlap among the three size classes at Morode may have resulted from food-resource partitioning. [ABSTRACT FROM AUTHOR]

The feeding associations of two wrasse species (Pseudolabrus; Labridae) with Goniistius zonatus (Cheilodactylidae) in two temperate water locations (Morode and Arakashi) in southern Japan were compared. At both locations, the wrasses accompanied G. zonatus so as to eat benthic invertebrates flushed out by the latter's feeding activities. Although the average feeding frequency of G. zonatus did not differ between the two locations, the host was more frequently and persistently followed at Morode, where foraging hosts often stayed at a calcareous-algal patch for a significant time and repeatedly pecked at the same site (repeated-feeding). At Arakashi, however, characterised by a poor calcareous-algal mat, G. zonatus usually took single sporadic bites at the substrate other than the algal mat while moving about (single-feeding). At both locations, the wrasses accompanied G. zonatus at higher rates when the latter was performing ‘repeated-feeding’ compared with ‘single-feeding’, with more frequent pecking by the attendant wrasses in the former association. The differences in feeding association between the two locations apparently resulted from the different patterns of feeding behavior by the host, in turn affected by the feeding substrate composition at each location. [ABSTRACT FROM AUTHOR]

While foraging on the substrate, two closely-related wrasses, Pseudolabrus eoethinus and P. sieboldi, which occur sympatrically in the Uwa Sea, Shikoku Island, Japan, often accompanied the morwong, Goniistius zonatus, eating benthic invertebrates flushed out by the latter's feeding activities. Both wrasses tended to feed more frequently in such an association than when solitary. Pseudolabrus eoethinus (9–17 cm TL) accompanied G. zonatus more frequently than the smaller P. sieboldi (7.5–12 cm TL), large individuals of the former attending the host more often than smaller ones. This tendency was not apparent in P. sieboldi. The size-dependent association frequency was determined by 1) the chances of encountering a host, and 2) interference among the wrasses. The frequency of encounter of wrasses with a host depended on the home range size of the former, such being positively correlated with body size. Interference among the wrasses resulted in smaller individuals being repelled by larger ones, irrespective of species, when they were approaching or attending a host. [ABSTRACT FROM AUTHOR]