Fish Predation Rate Research Articles

Comparing different farming habitats for mid-water rope nurseries to advance coral restoration efforts in the Maldives.

The need for comprehensive and effective coral restoration projects, as part of a broader conservation management strategy, is accelerating in the face of coral reef ecosystem decline. This study aims to expand the currently limited knowledge base for restoration techniques in the Maldives by testing the performance of mid-water rope nurseries in a lagoon and a reef habitat. We examined whether different coral farming habitats impacted fragment survival, health and growth of two coral genera and how the occurrence of mutualistic fauna, predation and disease influenced coral rearing success. Two nurseries were stocked with a total of 448 Pocillopora verrucosa and 96 Acropora spp. fragments, divided into different groups (four Pocillopora groups: lagoon nursery at 5 m; reef nursery at 5, 10 and 15 m; two Acropora groups: lagoon nursery at 5 m and reef nursery at 5 m). Eight fragment replicates from the same donor colony (Pocillopora genets: N = 14, Acropora genets N = 6) were used in each group and monitored for one year. Our results show that fragment survival was high in both farming habitats (>90%), with P. verrucosa surviving significantly better in the lagoon and Acropora spp. surviving and growing significantly faster in the reef nursery. P. verrucosa growth rates were similar between reef and lagoon habitat. Different rearing depths in the reef nursery had no impact on the survival of P. verrucosa but coral growth decreased considerably with depth, reducing fragments’ ecological volume augmentation and growth rates by almost half from 5 to 15 m depth. Further, higher fish predation rates on fragments were recorded on the reef, which did not impact overall nursery performance. Mutualistic fauna, which correlated positively with fragment survival, was more frequently observed in the lagoon nursery. The occurrence of disease was noted in both habitats, even though implications for fragment health were more severe in the lagoon. Overall, our study demonstrates that lagoon and reef nurseries are suitable for rearing large numbers of coral fragments for transplantation. Nevertheless, we recommend considering the specific environmental conditions of the farming habitat, in particular water quality and year-round accessibility, in each case and to adjust the coral farming strategy accordingly. We hope that this novel research encourages the increased application of mid-water rope nurseries for ‘coral gardening’ to advance coral reef recovery and climate resilience in the Maldives.

Combined effects of elevated epilimnetic temperature and metalimnetic hypoxia on the predation rate of planktivorous fish.

Increased temperature in the epilimnion and hypoxia in the metalimnion of a lake would result in an increase of positive-size-selective fish predation on zooplankton and in turn in a decrease of mean body size in zooplankton populations and communities. We tested this hypothesis in four types of experiments with juvenile rudd (Scardinius erythrophthalmus) foraging on Daphnia longispina in an indoor twin column tank system. In each experiment of the first three types, one column contained one of three types of experimental treatments differing from the control treatment (in the other column) by the following: (i) elevated temperature in the epilimnion, (ii) hypoxia in the metalimnion and (iii) simultaneous elevated temperature in the epilimnion and hypoxia in the metalimnion. In the fourth type of experiment, the gradients of temperature and oxygen concentration in both columns were the same, but prior to the experiments, Daphnia and fish in the control treatment were acclimated to normoxia and, in the experimental treatment, to hypoxia. The results confirmed our hypothesis, since the predation rate of fish was greater in each of the first three experimental treatments than in the control. We did not detect an effect of the acclimation to hypoxia on the predation rate of the fish.

Estimating the number of contributors to DNA mixtures provides a novel tool for ecology

Abstract Mixtures of DNA from multiple contributors present a novel opportunity to count individuals to inform fish and wildlife ecology. We apply a likelihood‐based framework to estimate the number of contributors to a DNA mixture for ecological applications. We then assess the performance of DNA mixture estimation through a combination of simulation analyses, laboratory testing, and a field trial to estimate fish predation rates from stomach content analysis. Simulations indicated reasonably sized genetic marker panels could estimate the number of contributors to mixtures comprised of up to 10 individuals, with potential to resolve larger mixtures with additional markers. Mixture estimates demonstrated robustness to common genotyping errors associated with fish and wildlife genetics applications. Laboratory trials demonstrated that DNA combined from multiple yellow perch (Perca flavescens) could be successfully genotyped with a 14‐loci microsatellite panel and led to successful estimation for up to 5‐contributor mixtures. Stomach content analysis with DNA mixtures indicated a 5‐fold increase in estimated predation rates of yellow perch by largemouth bass (Micropterus salmoides) relative to conventional visual assessment of diet contents which can miss partially digested prey items. DNA mixtures have potential to expand applications of count‐based ecological analyses. Technical challenges in generating genotypes from DNA mixtures may initially limit their use, however, advances in next generation genotyping platforms are anticipated to surmount these obstacles. Chiefly, we envision opportunity for DNA mixtures to advance eDNA analysis beyond presence/absence based inference to enumeration of specimens.

Minimal Model of Plankton Systems Revisited with Spatial Diffusion and Maturation Delay.

This study revisits the minimal model for a plankton ecosystem proposed by Scheffer with spatial diffusion of plankton and the delay of the maturation period of herbivorous zooplankton. It deepens our understanding of effects of the nutrients and the predation of fish upon zooplankton on the dynamical patterns of the plankton system and also presents new phenomena induced by the delay with spatial diffusion. When the nutrient level is sufficient low, the zooplankton population collapses and the phytoplankton population reaches its carrying capacity. Mathematically, the global stability of the boundary equilibrium is proved. As the nutrient level increases, the system switches to coexistent equilibria or oscillations depending on the maturation period of zooplankton and the predation rate of fish on herbivorous zooplankton. Under an eutrophic condition, there is a unique coexistent homogeneous equilibrium, and the equilibrium density of phytoplankton increases, while the equilibrium density of herbivorous zooplankton decreases as the fish predation rate on herbivorous zooplankton is increasing. The study shows that the system will never collapses under the eutrophic condition unless the fish predation rate approaches infinite. The study also finds a functional bifurcation relation between the delay parameter of the maturation period of herbivorous zooplankton and the fish predation rate on herbivorous zooplankton that, above a critical value of the fish predation rate, the system stays at the coexistent equilibrium, and below that value, the system switches its dynamical patterns among stable and unstable equilibria and oscillations. The oscillations emerge from Hopf bifurcations, and a detailed mathematical analysis about the Hopf bifurcations is carried out to give relevant ecological predications.

Influence of temperature and congener presence on habitat preference and fish predation in blue (Paralithodes platypus Brandt, 1850) and red (P. camtschaticus Tilesius, 1815) king crabs (Anomura: Lithodidae)

Rebuilding fisheries is a difficult process and many stocks that are declared overfished fail to recover even in the absence of fishing pressure. The Pribilof Islands stock of the blue king crab ( Paralithodes platypus Brandt, 1850) in Alaska, USA is one of these recovery failures. To explore how environmental and ecological factors might interact to suppress this stock, we conducted a suite of laboratory experiments to assess the effects of temperature changes and the presence of red king crab ( Paralithodes camtschaticus Tilesius, 1815) on blue king crab habitat preference and fish predation survival. Age-0 blue king crabs exhibited plasticity in habitat preference mediated by changes in water temperature, as well as the presence and density of juvenile red king crabs. While blue king crabs are often associated with shell-hash habitat, increases in water temperature, as well as the presence of red king crab at high densities, caused blue king crab juveniles to shift into habitats with an algal mimic present, a habitat type shown to reduce the predation efficacy of red king crabs. In contrast, red king crabs exhibited fewer changes in habitat preference with changes in water temperature and the presence of a congener. Blue king crabs are therefore behaviorally plastic, switching from strategies of predator avoidance when predator encounter rates are likely low, to predator deterrence strategies when encounter rates are higher. Fish predation trials further support the idea that blue king crabs are more focused on predator avoidance than are red king crabs. In fish predation trials run separately for the two crab species, blue king crabs had higher survival (60%) than red king crabs (33%) when exposed to fish predators. Our results indicate that age-0 blue king crabs can be less vulnerable to fish predation than red king crabs, but future research should assess how fish predation rates change when presented with higher densities of red and blue king crab in mixed assemblages as the observed habitat shifts could affect predation survival.

Controls of plankton production by pelagic fish predation and resource availability in the Alboran and Balearic Seas

A one-dimensional coupled physical and intermediate-complexity biochemical model comprising large and small phytoplankton and zooplankton groups, particulate organic nitrogen, ammonium and nitrate was developed to study the physical–biogeochemical interactions and parameters that control plankton production in the Alboran and Balearic Sea ecosystems. The model findings suggest that pelagic fish predation and resource availability through lateral and vertical nutrient inputs jointly characterize the plankton community structures. In agreement with previous observations, a typical annual plankton structure of the mesotrophic systems involves a vertically homogeneous biomass of large groups of phytoplankton and zooplankton within the upper 50-to-100m layer from mid-November to April and a subsurface biomass accumulation distributed roughly within 25–75m depths in the following months. Their light and temperature limitations constrain the smaller groups into the thermocline zone (25–50m) during late spring and summer. These obtained results were dependent on the zooplankton actively switching between preys (i.e., the food preference coefficients dependent on prey biomass). In the case of no switching, spurious dynamic equilibrium solutions may arise in the case of a constant and weak fish predation rate and using the quadratic predation formulation. The choice of a Holling Type II (i.e., hyperbolic) predation function may, however avoid ambiguous representation of the annual plankton structure in the case of a constant food preference choice under relatively weak predation pressures.

Foraging behaviour and prey consumption in the Indo-Pacific lionfish on Bahamian coral reefs

Predicting and mitigating the effects of invasive Indo-Pacific lionfish Pterois volitans on Caribbean fish communities requires a thorough understanding of the species' predation behaviour in the invaded range, including the types and amounts of prey consumed and how foraging patterns vary in relation to extrinsic conditions. We studied the activity levels and prey consumption rates of lionfish on 12 shallow coral reefs in the Bahamas in relation to time of day and prey availability. Lion- fish predation rates and activity levels were significantly higher during crepuscular (dawn and dusk) periods than at mid-day. Available prey fish biomass was highest at dawn but lower at mid-day and dusk, suggesting that lionfish predation activity is not limited by prey availability alone. Our cal - culated average daily mass-specific prey consumption rates, which incorporated daily variation, was ~3 times the estimates obtained from studies of captive lionfish in their native range and of invasive lionfish observed only during the day. Our results will help to predict more accurately the effect of predation by invasive lionfish on native reef fish communities.

Spatiotemporal Dynamics in a Spatial Plankton System

In this paper, we investigate the complex dynamics of a spatial plankton-fish system with Holling type III functional responses. We have carried out the analytical study for both one and two dimensional system in details and found out a condition for diffusive instability of a locally stable equilibrium. Furthermore, we present a theoretical analysis of processes of pattern formation that involves organism distribution and their interaction of spatially distributed population with local diffusion. The results of numerical simulations reveal that, on increasing the value of the fish predation rates, the sequences spots $\rightarrow$ spot-stripe mixtures$\rightarrow$ stripes$\rightarrow$ hole-stripe mixtures holes$\rightarrow$ wave pattern is observed. Our study shows that the spatially extended model system has not only more complex dynamic patterns in the space, but also has spiral waves.

Consequences of fish predation, migration, and juvenile ontogeny on zooplankton spring dynamics

In order to disentangle if and when resource supply and adult and young‐of‐the‐year (0+) fish predation affect zooplankton dynamics during spring, we monitored zooplankton during three consecutive years in a lake in southern Sweden. We also experimentally assessed 0+ fish predation rates and estimated changes in predation rates of adult fish on zooplankton. Decline in abundances of large‐sized zooplankters in early spring was not caused by 0+ fish predation. Instead, this decline was most likely a combined result of size‐selective predation from adult fish (stationary in the lake and from those returning from surrounding streams) and competition for diminishing algal food resources. On the other hand, the decline in medium‐sized zooplankton in the lake during spring was strongly affected by 0+ fish. Hence, during spring, zooplankton are facing predation both from adult fish selecting large prey and from 0+ fish, which start feeding on small‐sized prey and eventually switch to larger. Neither predation by different ontogenetic stages of fish (adult and 0+) nor resource supply shape the zooplankton spring dynamics, but rather they affect the timing and strength of these events. 0+ cyprinids tend to have stronger effect on zooplankton dynamics than other taxa of 0+ fish. A combination of predation from adult and 0+ fish during spring is the main mechanism behind the crash of the zooplankton community, which in many lakes leads to the termination of the clear‐water phase.

Optimal Control of a Nutrient-Phytoplankton-Zooplankton-Fish System

We consider the mathematical formulation, analysis, and numerical solution of an optimal control problem for a nonlinear “nutrient-phytoplankton-zooplankton-fish” reaction-diffusion system. We study the existence of optimal solutions, derive an optimality system, and determine optimal solutions. In the original spatially homogeneous formulation [M. Scheffer, Oikos, 62 (1991), pp. 271–282] the dynamics of plankton were investigated as a function of parameters for nutrient levels and fish predation rate on zooplankton. In our paper the model is spatially extended and the parameter for fish predation treated as a multiplicative control variable. The model has implications for the biomanipulation of food-webs in eutrophic lakes to help improve water quality. In order to illustrate the control of irregular spatiotemporal dynamics of plankton in the model we implement a semi-implicit (in time) finite element method with “mass lumping” and present the results of numerical experiments in two space dimensions.

Study of the nutrient and plankton dynamics in Lake Tanganyika using a reduced-gravity model

An eco-hydrodynamic (ECOH) model is proposed for Lake Tanganyika to study the plankton productivity. The hydrodynamic sub-model solves the non-linear, reduced-gravity equations in which wind is the dominant forcing. The ecological sub-model for the epilimnion comprises nutrients, primary production, phytoplankton biomass and zooplankton biomass. In the absence of significant terrestrial input of nutrients, the nutrient loss is compensated for by seasonal, wind-driven, turbulent entrainment of nutrient-rich hypolimnion water into the epilimnion, which gives rise to high plankton productivity twice in the year, during the transition between two seasons. Model simulations predict well the seasonal contrasts of the measured physical and ecological parameters. Numerical tests indicate that the half saturation constant for grazing by zooplankton and the fish predation rate on zooplankton affect the zooplankton biomass measurably more than that of phytoplankton biomass. This work has implications for the application of this model to predict the climatological biological productivity of Lake Tanganyika.

Relationships among predatory fish, sea urchins and barrens in Mediterranean rocky reefs across a latitudinal gradient

Previous studies conducted on a local scale emphasised the potential of trophic cascades in Mediterranean rocky reefs (involving predatory fish, sea urchins and macroalgae) in affecting the transition between benthic communities dominated by erected macroalgae and barrens (i.e., bare rock with partial cover of encrusting algae). Distribution patterns of fish predators of sea urchins (Diplodus sargus sargus, Diplodus vulgaris, Coris julis and Thalassoma pavo), sea urchins (Paracentrotus lividus and Arbacia lixula) and barrens, and fish predation rates upon sea urchins, were assessed in shallow (3-6m depth) sublittoral rocky reefs in the northern, central and southern sectors of the eastern Adriatic Sea, i.e., on a large spatial scale of hundreds of kilometres. No dramatic differences were observed in predatory fish density across latitude, except for a lower density of small D. sargus sargus in the northern Adriatic and an increasing density of T. pavo from north to south. P. lividus did not show any significant difference across latitude, whereas A. lixula was more abundant in the southern than in the central Adriatic. Barrens were more extended in the southern than in the central and northern sectors, and were related with sea urchin density. Fish predation upon adult sea urchins did not change on a large scale, whereas it was slightly higher in the southern sector for juveniles when predation rates of both urchins were pooled. Results show that: (1) assemblages of predatory fish and sea urchins, and barren extent change across latitude in the eastern Adriatic Sea, (2) the weak relations between predatory fish density and predation rates on urchins reveal that factors other than top-down control can be important over large scale (with the caveat that the study was conducted in fished areas) and (3) patterns of interaction among strongly interacting taxa could change on large spatial scales and the number of species involved.

Influence of epiphytic algal coverage on fish predation rates in simulated eelgrass habitats.

1. Hughes, J. E., L. A. Deegan, J. C. Wyda, M. J. Weaver, and A. Wright. 2002. Estuaries 25: 235–249. 2. Wyda, J. C., L. A. Deegan, J. E. Hughes, and M. J. Weaver. 2002. Estuaries 25: 86–100. 3. Raposa, K. B., and C. A. Oviatt. 2000. Estuaries 23: 46–55. 4. Zacharias, M. A., and J. C. Roff. 2001. J. Biogeogr. 28: 471– 483. 5. Heck, K. L. Jr., K. W. Able, M. P. Fahay, and C. T. Roman. 1989. Estuaries 12: 59–65. 6. Nagelkerken, I., G. van der Velde, M. W. Gorissen, G. J. Meijer, T. van’t Hof, and C. den Hartog. 2000. Estuar. Coast. Shelf Sci. 51: 31–44. 7. Lenanton, R. C., and I. C. Potter. 1987. Estuaries 10: 28–35. 8. Lenanton, R. C. 1982. Aust. J. Mar. Freshw. Res. 33: 881–900. 9. Able, K. W., and M. P. Fahay. 1988. Pp. 38–246 in The First Year in the Life of Estuarine Fishes in the Middle Atlantic Bight. Rutgers University Press, New Brunswick, NJ. 10. Sokal, R. R., and F. J. Rohlf. 1995. Pp. 241-42 in Biometry. WH Freeman, New York.

The impact of detritivorous fishes on a mangrove estuarine system

Sundarban mangrove ecosystem in India is one of the largest detritus based ecosystem of the world and it supplies the detritus and nutrients to the adjacent Hooghly-Matla estuarine complex. In this estuary a group of fish completely detritivorous in nature, belonging to the genus Mugil spp. is present. This group of fish is expected to have important effects on the trophic dynamics of ecosystems, but exact nature of these effects is not known. In order to study the impact that detritivory by fish may have on the estuarine food chain, we developed mathematical formulations. We run two models, one with phytoplankton, zooplankton, carnivorous fish, detritus and nutrient and without this group of fish and a second one after including this fish in the system. In our model this group of fish has no major impact on primary productions of the estuarine system but has extensive role in total fish production. Coexistence of detritivorous fish and carnivorous fish occurs within reasonable parameter range. We have tested different growth rates of phytoplankton, grazing rates and predation rates of zooplankton, detritivorous fish and carnivorous fish for total system equilibrium. Carnivorous fish predation rate on detritivorous fish and detritivorous fish grazing rate on detritus are very important. Different foraging ratios are also tested in this study. Foraging preference of carnivorous fish on detritivorous fish appears significant for the system equilibrium.

Chaos and fractals in fish school motion

The once abstract notions of fractal patterns and processes now appear naturally and inevitably in various chaotic dynamical systems. The examples range from Brownian motion [1–5] to the dynamics of social relations [6]. In this paper, after introducing a certain hybrid mathematical model of the plankton–fish school interplay, we study the fractal properties of the model fish school walks. We show that the complex planktivorous fish school motion is dependent on the fish predation rate. A decrease in the rate is followed by a transition from low-persistent to high-persistent fish school walks, i.e., from a motion with frequent to a motion with few changes of direction. The low-persistent motion shows fractal properties for all time scales, whereas the high-persistent motion has pronounced multifractal properties for large-scale displacements.

Fish and Plankton Interplay Determines Both Plankton Spatio-Temporal Pattern Formation and Fish School Walks: A Theoretical Study

The fascinating variety of spatio-temporal patterns in aquatic ecosystems and the understanding of the governing mechanisms of its generation and further dynamics requires ongoing experimental and theoretical studies. After introducing a certain hybrid mathematical model, this paper makes an attempt to demonstrate that the predation of a mobile planktivorous fish school on zooplankton can initiate both plankton pattern formation and fish school walks. Nonlinear interactions in the model of a fish-zooplankton-algae trophic chain prevent a simple intuitive understanding of the system dynamics. It is shown that the fish school predation and motion can give rise to plankton spiral waves. In the course of the spiral wave formation, the amplitudes of the spatially averaged plankton density oscillations are decreasing dramatically. Fish school walks are shown to resemble a fractional Brownian motions with a Hurst exponent depending on the fish predation rate.