Fish predators control outbreaks of Crown-of-Thorns Starfish

Outbreaks of corallivorous Crown-of-Thorns Starfish (CoTS, Acanthaster spp.) have caused persistent and widespread loss of coral cover across Indo-Pacific coral reefs. The potential drivers of these outbreaks have been debated for more than 50 years, hindering effective management to limit their destructive impacts. Here, we show that fish biomass removal through commercial and recreational fisheries may be a major driver of CoTS population outbreaks. CoTS densities increase systematically with increasing fish biomass removal, including for known CoTS predators. Moreover, the biomass of fish species and families that influence CoTS densities are 1.4 to 2.1-fold higher on reefs within no-take marine reserves, while CoTS densities are 2.8-fold higher on reefs that are open to fishing, indicating the applicability of fisheries-based management to prevent CoTS outbreaks. Designing targeted fisheries management with consideration of CoTS population dynamics may offer a tangible and promising contribution to effectively reduce the detrimental impacts of CoTS outbreaks across the Indo-Pacific.

Can Identifying Discrete Behavioral Groups With Individual-Based Acoustic Telemetry Advance the Understanding of Fish Distribution Patterns?

Identifying patterns of organismal distribution can provide valuable insights for basic and applied marine and coastal ecology because understanding where animals are located is foundational to both research and science-based conservation. Understanding variation in distributional patterns can lead to a better assessment of ecological drivers and an improved ability to predict consequences of natural and altered relationships. Here, our purpose is to explore if quantifying coexisting groups of individual fish predators advances our understanding of field distribution patterns. Toward this end, we quantified locations of 59 acoustically tagged striped bass (Morone saxatilis) within a 26-stationary unit telemetry receiver array in Plum Island Estuary (PIE), MA, United States. We then used cluster analyses on spatial and temporal-spatial metrics from this dataset to (1) assess if distinct groups of individuals coexisted, (2) quantify group characteristics, and (3) test associations between groups and distribution (e.g., physical site type and region). Based on multiple lines of evidence, we identified four groups of striped bass with different space use patterns that persisted across seasons (summer and fall). Similar-sized striped bass clustered at spatial and temporal scales at which individuals within distinct groups could, and did, physically overlap. In addition, distributional groups were linked to components of physical site type and region suggesting that discrete groups of individuals can interact differently with the environment within the same ecological system. The identification of these distinct groups of individuals creates a baseline from which to explore further ecological implications of grouping behavior for research and conservation in geographically large, temporally dynamic, and spatially heterogeneous marine and coastal environments.

Heavy Metals in Liver, Kidney, Brain and Muscle: Health Risk Assessment for Consumption of Edible parts of Birds from the Chahnimeh Reservoirs Sistan (Iran)

The concentrations of four heavy metals zinc (Zn), lead (Pb), nickel (Ni) and cadmium (Cd) were determined in liver, kidney, muscle and brain of nine species of birds from the Chahmimeh Sistan from Iran, to assess metal levels and the potential risk to birds, and to the people who eat them. Significantly higher levels of all metals were found in the brain of waterfowl than in the tissues of other birds. There were no significant gender differences in heavy metals in all tissue. Levels of Pb, Cd, Ni and Zn in the liver and kidney varied as a function of feeding habitats; the median levels were significantly higher in invertebrate predators than fish predators and omnivorous species. Short distance migrating birds had significantly higher median levels of heavy metals in liver and kidney than long distance migrant birds. Ni levels in liver and kidney tissues in 56% of birds were higher than the critical thresholds levels for effects in birds. Our data indicate that environmental exposure to metals were higher in the wintering populations of birds in the Chahnimeh of Sistan from Iran. Concentration Zn, Pb and Cd in a small percentage of birds, and 56% nickel level in liver and 56% kidney concentrations in birds, were above toxicity levels. Determining the exposure frequency and daily intake of birds, the Hazard Quotient for edible tissues (kidney, Liver and muscle) of these birds showed that their consumption provides a health risk to people consuming them.

Heavy Metals in Liver, Kidney, Brain and Muscle: Health Risk Assessment for Consumption of Edible parts of Birds from the Chahnimeh reservoirs Sistan (Iran)

The concentrations of four heavy metals zinc (Zn), lead (Pb), nickel (Ni) and cadmium (Cd) were determined in liver, kidney, muscle and brain of nine species of birds from the Chahmimeh Sistan from Iran, to assess metal levels and the potential risk to birds, and to the people who eat them. Higher levels of all metals were found in the brain of waterfowl than in the tissues of other birds (P < 0.05). There were no significant gender differences in heavy metals in all tissue. Levels of Pb, Cd, Ni and Zn in the liver and kidney varied as a function of feeding habitats; the median levels were higher in invertebrate predators than fish predators and omnivorous species (P < 0.05). Short distance migrating birds had higher median levels of heavy metals in liver and kidney than long distance migrant birds (P < 0.05). Ni levels in liver and kidney tissues in 56% of birds were higher than the critical thresholds levels for effects in birds. Our data indicate that environmental exposure to metals were higher in the wintering populations of birds in the Chahnimeh of Sistan from Iran. Concentration Zn, Pb and Cd in a small percentage of birds, and 56% nickel level in liver and 56% kidney concentrations in birds, were above toxicity levels. Examination EDI, EWI and HQ of the edible tissues (kidney, Liver and muscle) of these birds showed that their consumption is a threat to the health of the people of the region.

Ethnoichthyological Study of Biological Characteristics and Ecology (Salminus brasiliensis: Teleostei/Characiform): Importance, Status and Conservation Challenges in the Region of Mato Grosso, Brazil

Introduction: Salminus is a genus of ichthyofauna currently constituted by five species of migratory neotropical fish, predators, which are important in commercial, ecological and sport fishing. Aims: The article reflects the conception of fishermen about the ecological interrelationships of ichthyofauna, the relationship with sport fishing, aspects of trophic interactions among fish, the use of habitats aimed at feeding or reproduction and relations with fishing activity. Methodology: Study carried out in the state of Mato Grosso, central region of Brazil. 122 fishing professionals and artisanal fishermen were interviewed. The testimonies were obtained through phonographic interviews, carried out during visits in temperate sport fishing from 2018 to 2020, verifying questions related to fishing and the study specimen S. brasiliensis. Results: Among the interviewees, 37 were sport fishermen (30.3%), 22 artisanal fishermen (18.1%) and 63 guide fishermen (51.6%). The interviewees reported several situations and approaches on the problems generated by sport fishing in the State. The results were consistent with the scientific literature and revealed detailed knowledge about the survival strategies of S. brasiliensis. The answers revealed the fishermen's observations on the decrease in fishing resources, the scarcity of species and the conflicts related to sport fishing, making it necessary to look for the best ways of recovering and conserving native species and monitoring in the surveyed places. Conclusion: S. brasiliensis is an example of the ichthyofauna that is much sought after by sport fishing. The interviewees demonstrated important perceptions of the changes that are occurring in the rivers of Mato Grosso and it was found that it is necessary to intensify studies looking for ways to recover and conserve the native ichthyofauna in the region. The results obtained aim to promote social contributions and partnerships with professional and artisanal fishermen, encouraged to achieve a better harmony between fishing and nature, creating actions that can be extended to indigenous, quilombola and riverside peoples.

Predator–Prey Interactions Examined Using Lionfish Spine Puncture Performance

Synopsis Puncture mechanics can be studied in the context of predator–prey interactions and provide bioinspiration for puncture tools and puncture-resistant materials. Lionfish have a passive puncture system where venomous spines (dorsal, anal, and pelvic), the tool, may embed into a predator’s skin, the target material, during an encounter. To examine predator–prey interactions, we quantified the puncture performance of red lionfish, Pterois volitans, spines in buccal skin from two potential predators and porcine skin, a biological model for human skin. We punctured dorsal, anal, and pelvic lionfish spines into three regions of buccal skin from the black grouper (Mycteroperca bonaci) and the blacktip shark (Carcharhinus limbatus), and we examined spine macro-damage (visible without a microscope) post puncture. Lionfish spines were more effective, based on lower forces measured and less damage incurred, at puncturing buccal skin of groupers compared to sharks. Anal and dorsal spines incurred the most macro-damage during successful fish skin puncture trials, while pelvic spines did not incur any macro-damage. Lionfish spines were not damaged during porcine skin testing. Anal spines required the highest forces, while pelvic spines required intermediate forces to puncture fish skin. Dorsal spines required the lowest forces to puncture fish skins, but often incurred macro-damage of bent tips. All spine regions required similar forces to puncture porcine skin. These data suggest that lionfish spines may be more effective at puncturing humans such as divers than potential fish predators. These results emphasize that puncture performance is ultimately determined by both the puncture tool and target material choice. Lionfish puncture performance varies among spine region, when taking into account both the puncture force and damage sustained by the spine.

Temperature effects on metabolic scaling of a keystone freshwater crustacean depend on fish-predation regime

ABSTRACTAccording to the metabolic theory of ecology, metabolic rate, an important indicator of the pace of life, varies with body mass and temperature as a result of internal physical constraints. However, various ecological factors may also affect metabolic rate and its scaling with body mass. Although reports of such effects on metabolic scaling usually focus on single factors, the possibility of significant interactive effects between multiple factors requires further study. In this study, we show that the effect of temperature on the ontogenetic scaling of resting metabolic rate of the freshwater amphipod Gammarus minus depends critically on habitat differences in predation regime. Increasing temperature tends to cause decreases in the metabolic scaling exponent (slope) in population samples from springs with fish predators, but increases in population samples from springs without fish. Accordingly, the temperature sensitivity of metabolic rate is not only size-specific, but also its relationship to body size shifts dramatically in response to fish predators. We hypothesize that the dampened effect of temperature on the metabolic rate of large adults in springs with fish, and of small juveniles in springs without fish are adaptive evolutionary responses to differences in the relative mortality risk of adults and juveniles in springs with versus without fish predators. Our results demonstrate a complex interaction among metabolic rate, body mass, temperature and predation regime. The intraspecific scaling of metabolic rate with body mass and temperature is not merely the result of physical constraints related to internal body design and biochemical kinetics, but rather is ecologically sensitive and evolutionarily malleable.

Density- and trait-mediated effects of fish predators on amphipod grazers: potential indirect benefits for the giant kelp Macrocystis pyrifera

Indirect effects of predators on primary producers may arise when predators suppress herbivore abundance and/or alter the behaviour patterns of herbivores in ways that reduce grazing pressure. Most studies highlight the role of predators in reducing herbivore abundance (i.e. density- mediated interactions), while behavioural effects (i.e. trait-mediated interactions) induced by predators are less commonly considered and are often assumed to be of secondary importance. We used a mesocosm experiment to evaluate the consumptive and behavioural effects of 2 species of predatory fishes on amphipod grazers that feed and nest on the giant kelp Macrocystispyrifera. Only one, Noto- labrus celidotus, of the 2 predator species reduced grazer abundance. Although the second predator species, N. fucicola, did not affect grazer abundance directly, it significantly reduced the grazing efficiency of amphipods on blades of M. pyrifera. Our study illustrates how density- and trait-mediated interactions reduce grazer efficiency and provide potential indirect benefits to primary producers. To our knowledge, this is the first experimental evidence of a potential trophic cascade in kelp beds generated by consumptive and nonconsumptive effects. When considered alongside results of other studies that highlight positive effects of macroalgae on reef fish demographic rates, our results provide compelling evidence that mutualistic relationships may exist between kelp and associated predatory fishes. © Inter-Research 2010.

Density- and trait-mediated effects of fish predators on amphipod grazers: potential indirect benefits for the giant kelp Macrocystis pyrifera

Indirect effects of predators on primary producers may arise when predators suppress herbivore abundance and/or alter the behaviour patterns of herbivores in ways that reduce grazing pressure. Most studies highlight the role of predators in reducing herbivore abundance (i.e. density- mediated interactions), while behavioural effects (i.e. trait-mediated interactions) induced by predators are less commonly considered and are often assumed to be of secondary importance. We used a mesocosm experiment to evaluate the consumptive and behavioural effects of 2 species of predatory fishes on amphipod grazers that feed and nest on the giant kelp Macrocystispyrifera. Only one, Noto- labrus celidotus, of the 2 predator species reduced grazer abundance. Although the second predator species, N. fucicola, did not affect grazer abundance directly, it significantly reduced the grazing efficiency of amphipods on blades of M. pyrifera. Our study illustrates how density- and trait-mediated interactions reduce grazer efficiency and provide potential indirect benefits to primary producers. To our knowledge, this is the first experimental evidence of a potential trophic cascade in kelp beds generated by consumptive and nonconsumptive effects. When considered alongside results of other studies that highlight positive effects of macroalgae on reef fish demographic rates, our results provide compelling evidence that mutualistic relationships may exist between kelp and associated predatory fishes. © Inter-Research 2010.