scholarly journals Indirect versus Direct Effects of Freshwater Browning on Larval Fish Foraging

2019 ◽  
Author(s):  
Dina M. Leech ◽  
Troy L. Clift ◽  
Jessica L. Littlefield ◽  
Nicholas R. Ravagli ◽  
Jacob E. Spain
Keyword(s):  
Largemouth Bass ◽  
Indirect Effects ◽  
Prey Availability ◽  
Larval Fish ◽  
Light Availability ◽  
Direct Effects ◽  
Feeding Rates ◽  
Growth And Survival ◽  
Feeding Experiments ◽  
Fish Spawning

ABSTRACTFish foraging and energy flow are both predicted to decline with freshwater ‘browning’ due to reductions in light availability. Studies investigating these predictions have focused on juveniles and adults; however, the larval stage represents a ‘critical period’ in fish development. We investigated the indirect versus direct effects of browning on zooplankton-larval fish interactions by altering water color with SuperHume (absorbance at 440 nm = 1.6 – 10.8 m−1). Phytoplankton and zooplankton densities were monitored across experimental tanks in the laboratory for one month leading up to fish spawning. Larval largemouth bass were then introduced to assess indirect effects on fish feeding rates and growth. Direct effects on foraging of largemouth bass and bluegill were determined with separate short-term feeding experiments. Browning did not directly alter the ability of larval fish to capture prey. However, significant indirect effects on larval fish foraging, growth, and survival were observed as phytoplankton and zooplankton decreased with increased browning. Our data suggest lake browning will reduce energy transfer to larval fish due to a reduction in prey availability but not visual foraging.

scholarly journals Indirect versus Direct Effects of Freshwater Browning on Larval Fish Foraging

2021 ◽  
Author(s):  
Dina M. Leech ◽  
Troy L. Clift ◽  
Jessica L. Littlefield ◽  
Nicholas R. Ravagli ◽  
Jacob E. Spain
Keyword(s):  
Largemouth Bass ◽  
Indirect Effects ◽  
Prey Availability ◽  
Larval Fish ◽  
Light Availability ◽  
Trophic Levels ◽  
Zooplankton Abundance ◽  
Direct Effects ◽  
Growth And Survival ◽  
Visual Foraging

Fish foraging and energy flow between trophic levels are predicted to decline with freshwater browning due to decreased light availability. Studies investigating these predictions have focused on juvenile and adult fishes; however, the larval stage represents a ‘critical period’ in development. We investigated the indirect (i.e., prey availability) versus direct (i.e., visual foraging) effects of browning on zooplankton-larval fish interactions by altering water color with SuperHume (absorbance at 440 nm = 1.6 – 10.8 m-1). Phytoplankton and zooplankton densities were monitored across treatments for one month to simulate the time leading up to fish spawning in the spring. Larval largemouth bass were then introduced to assess indirect effects on fish feeding, growth, and survival. Direct effects on largemouth bass and bluegill foraging on zooplankton were determined with separate short-term experiments. Browning did not directly alter the ability of larvae to capture prey. However, indirect effects on larval fish foraging, growth, and survival were observed as phytoplankton and zooplankton abundance decreased with increased browning. Our data suggest browning may reduce energy transfer to larval fish due to a reduction in prey but not visual foraging.

scholarly journals Effects of Microplastics on the Feeding Rates of Larvae of a Coastal Fish: Direct Consumption, Trophic Transfer, and Effects on Growth and Survival

2021 ◽  
Author(s):  
Christine Uy ◽  
Darren Johnson
Keyword(s):  
Larval Fish ◽  
Trophic Transfer ◽  
Control Group ◽  
Feeding Rates ◽  
Lower Growth ◽  
Larval Phase ◽  
Coastal Fish ◽  
Growth And Survival ◽  
Low Concentrations ◽  
High Concentrations

Abstract Microplastics are now found throughout the world’s oceans, and although many organisms ingest microplastics, less is known about how plastics in seawater may affect key processes such as feeding rate, growth, and survival. We used a series of laboratory experiments to test whether microplastics in seawater affected the feeding rates of larvae of the California Grunion, Leuresthes tenuis. In addition, we tested whether trophic transfer of microplastics from zooplankton to larval fish can occur and affect growth and survival of fish. We measured feeding rates of grunion larvae at various concentrations of 75–90 µm and 125–250 µm polyethylene microplastics and under both still water and turbulent conditions. In these experiments, exposure to microplastics had modest effects on feeding rates, though responses may be somewhat complex. Low concentrations of microplastics increased feeding rates compared to the control, but at higher concentrations, feeding rates were indistinguishable from those in the control group though effects were small compared to natural variation in feeding rates among individual fish. Experiments to test for trophic transfer of microplastics revealed that grunion larvae that were fed brine shrimp exposed to high concentrations of microplastics had lower growth rates and elevated mortality rates. Overall, our results suggest that the direct effects of microplastics on feeding rates of California Grunion during the early larval phase are minor, while the trophic transfer of microplastics from zooplankton to larval fish may have significant effects on their growth and survival.

scholarly journals Some like it hot, hungry tunas do not! Implications of temperature and plankton food web dynamics on growth and diet of tropical tuna larvae

2020 ◽  
Author(s):  
Miram R Gleiber ◽  
Su Sponaugle ◽  
Robert K Cowen
Keyword(s):  
High Temperature ◽  
Food Web ◽  
Prey Availability ◽  
Larval Fish ◽  
Individual Growth ◽  
Calanoid Copepods ◽  
Growth And Survival ◽  
Straits Of Florida ◽  
Food Web Dynamics ◽  
Tropical Tuna

Abstract Restricted to low-productivity environments near their thermal maxima, larval tunas may be threatened by warming global temperatures, yet our understanding of how they are constrained is limited. We examined blackfin tuna (Thunnus atlanticus, presumptive) diet and growth in the context of their prey and predators in the Straits of Florida in 2 years with contrasting summer conditions: low temperature (26.7–28.3°C)–high prey and high temperature (28.4–29.0°C)–low prey. In the cooler, high-prey conditions, larvae had 30% faster growth (0.45 mm d−1), fuller guts from predominantly feeding on calanoid copepods, and were 10× more abundant, dominating the larval fish assemblage. In contrast, in warm, low-prey conditions fewer, younger, and slower-growing (0.35 mm d−1) T. atlanticus fed predominantly on nauplii and had less full guts. Modelling individual growth across years revealed that growth peaked at an optimum of 28.5°C (5°C below known thermal maxima in the field) and high densities of predators selectively consumed slower-growing larvae. Low-prey availability may reduce the thermal optima of larvae, as growth and survival are diminished when low prey and high temperature coincide. Our results illustrate the importance of considering food web dynamics with temperature when predicting the response of organisms to ecosystem variability, particularly ongoing climate change.

Balancing Fisheries Management and Water Uses for Impounded River Systems

2008 ◽  
Keyword(s):  
Food Web ◽  
Largemouth Bass ◽  
Standing Crop ◽  
Size Structure ◽  
Prey Availability ◽  
Micropterus Salmoides ◽  
Adult Population ◽  
Fish Prey ◽  
Growth And Survival ◽  
Southern Florida

<em>Abstract</em>.—Growth and survival of stocked fish are positively influenced by the availability of suitably sized prey fish. We examined relationships among juvenile largemouth bass <em>Micropterus salmoides </em>size structure, occurrence of piscivory, and biomass relative to fish prey size structure and biomass across Florida’s latitudinal gradient to evaluate potential fish prey availability across a broad spatial scale of lakes. We sampled the 2003 and 2004 largemouth bass year-classes and potential fish prey in April/May (i.e., spring) and in June/July (i.e., summer) in six study lakes distributed from northern to southern Florida. Available prey to predator ratios (AP:P) decreased with increased fish size but indicated that prey resources were not limiting at any lake during either year (all AP:P > 8). We used a biomass-based food web model for our lake with the lowest AP:P we measured (~9) to determine if bioenergetics-based predictions agreed with AP:P metric indications of the system’s potential to support a higher standing crop of largemouth bass. Food web simulations showed potential to increase the standing crop of adult largemouth bass population by up to 30% at high stocking rates (i.e., 150 fish/ha), but stocking at high rates resulted in decreases to the natural portion of the adult population. Available prey metrics and simulations can provide information on the potential for stocking success, which could be used to improve the efficacy of stocking programs.

scholarly journals The role of kelp crabs as consumers in bull kelp forests—evidence from laboratory feeding trials and field enclosures

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e3372 ◽  
Author(s):  
Katie Dobkowski
Keyword(s):  
Feeding Preference ◽  
Kelp Forests ◽  
Feeding Rates ◽  
Salish Sea ◽  
Growth And Survival ◽  
Kelp Beds ◽  
San Juan Islands ◽  
Feeding Experiments ◽  
Feeding Trials ◽  
Ne Pacific

The Northern kelp crab (Pugettia producta) and the graceful kelp crab (Pugettia gracilis) are common primary consumers in bull kelp beds near the San Juan Islands (Salish Sea, NE Pacific). In this system, urchins (often considered the most voracious herbivores exerting top-down control on kelp beds) tend to remain sedentary because of the high availability of detrital macroalgae, but the extent to which kelp crabs consume kelp (and other food options) is largely unknown. I conducted four types of laboratory feeding experiments to evaluate kelp crab feeding patterns: (1) feeding electivity between bull kelp (Nereocystis luetkeana) and seven species of co-occurring local macroalgae; (2) feeding electivity on aged vs. fresh bull kelp; (3) feeding preference between N. luetkeana and small snails (Lacuna sp.); and (4) scaling of feeding rate with body size in P. producta and P. gracilis. In choice experiments, P. producta consumed greater mass of N. luetkeana than of other macroalgal species offered and elected to eat fresh bull kelp over aged. However, P. producta also consumed snails (Lacuna sp.), indicating more generalized feeding than previously suspected. Feeding rates for P. producta exceeded the expected 3∕4 scaling rule of metabolic rates, indicating that larger P. producta may have a disproportionately large impact on bull kelp. A subtidal field experiment, designed to assess the influence of consumers on juvenile bull kelp net tissue gain, found that only fully enclosed (protected) bull kelp increased in wet mass and blade length. Herbivory by kelp crabs, among other consumers, is likely to play a previously unrecognized role in mediating the growth and survival of this annual kelp species within the Salish Sea.

scholarly journals Direct and indirect responses of a freshwater food web to a potent synthetic oestrogen

2014 ◽  
Vol 369 (1656) ◽  
pp. 20130578 ◽  
Author(s):  
Karen A. Kidd ◽  
Michael J. Paterson ◽  
Michael D. Rennie ◽  
Cheryl L. Podemski ◽  
Dave L. Findlay ◽  
...  
Keyword(s):  
Indirect Effects ◽  
Fathead Minnow ◽  
Lake Trout ◽  
Prey Availability ◽  
Pimephales Promelas ◽  
Endocrine Disrupting Chemicals ◽  
Benthic Invertebrate ◽  
Small Scale ◽  
Direct Effects ◽  
Experimental Lakes Area

Endocrine-disrupting chemicals (EDCs) in municipal effluents directly affect the sexual development and reproductive success of fishes, but indirect effects on invertebrate prey or fish predators through reduced predation or prey availability, respectively, are unknown. At the Experimental Lakes Area in northwestern Ontario, Canada, a long-term, whole-lake experiment was conducted using a before-after-control-impact design to determine both direct and indirect effects of the synthetic oestrogen used in the birth control pill, 17α-ethynyloestradiol (EE2). Algal, microbial, zooplankton and benthic invertebrate communities showed no declines in abundance during three summers of EE2 additions (5–6 ng l −1 ), indicating no direct toxic effects. Recruitment of fathead minnow ( Pimephales promelas ) failed, leading to a near-extirpation of this species both 2 years during (young-of-year, YOY) and 2 years following (adults and YOY) EE2 additions. Body condition of male lake trout ( Salvelinus namaycush ) and male and female white sucker ( Catostomus commersonii ) declined before changes in prey abundance, suggesting direct effects of EE2 on this endpoint. Evidence of indirect effects of EE2 was also observed. Increases in zooplankton, Chaoborus , and emerging insects were observed after 2 or 3 years of EE2 additions, strongly suggesting indirect effects mediated through the reduced abundance of several small-bodied fishes. Biomass of top predator lake trout declined by 23–42% during and after EE2 additions, most probably an indirect effect from the loss of its prey species, the fathead minnow and slimy sculpin ( Cottus cognatus ). Our results demonstrate that small-scale studies focusing solely on direct effects are likely to underestimate the true environmental impacts of oestrogens in municipal wastewaters and provide further evidence of the value of whole-ecosystem experiments for understanding indirect effects of EDCs and other aquatic stressors.

Trophic Cascades in Grasslands

2018 ◽  
Author(s):  
Brian J. Wilsey
Keyword(s):  
Indirect Effects ◽  
Prey Species ◽  
Trophic Levels ◽  
Herbaceous Plant ◽  
Direct Effects ◽  
Temperate Grasslands ◽  
Cascading Effect ◽  
Top Predators ◽  
Invertebrate Predators ◽  
Ecology Of Fear

Top predators have effects that can ‘cascade down’ on lower trophic levels. Because of this cascading effect, it matters how many trophic levels are present. Predators are either ‘sit and wait’ or ‘active’. Wolves are top predators in temperate grasslands and can alter species composition of smaller-sized predators, prey, and woody and herbaceous plant species, either through direct effects or indirect effects (‘Ecology of Fear’). In human derived grasslands, invertebrate predators fill a similar ecological role as wolves. Migrating populations of herbivores tend to be more limited by food than non-migratory populations. The phenology and synchrony of births vary among prey species in a way that is consistent with an adaptation to predation. Precocious species have highly synchronous birth dates to satiate predators. Non-precocious species (‘hiders’) have asynchronous births. Results from studies that manipulate both predators and food support the hypothesis that bottom-up and top-down effects interact.

Differential effects of turbidity on prey consumption of piscivorous and planktivorous fish

2003 ◽  
Vol 60 (12) ◽  
pp. 1517-1526 ◽  
Author(s):  
Alex De Robertis ◽  
Clifford H Ryer ◽  
Adriana Veloza ◽  
Richard D Brodeur
Keyword(s):  
Light Intensity ◽  
Prey Capture ◽  
High Light Intensity ◽  
Prey Consumption ◽  
Planktivorous Fish ◽  
Oncorhynchus Keta ◽  
Feeding Rates ◽  
Anoplopoma Fimbria ◽  
Piscivorous Fish ◽  
Feeding Experiments

Contrast degradation theory predicts that increased turbidity decreases the visibility of objects that are visible at longer distances more than that of objects that are visible at short distances. Consequently, turbidity should disproportionately decrease feeding rates by piscivorous fish, which feed on larger and more visible prey than particle-feeding planktivorous fish. We tested this prediction in a series of laboratory feeding experiments, the results of which indicated that prey consumption by two species of planktivorous fish (juvenile chum salmon (Oncorhynchus keta) and walleye pollock (Theragra chalcogramma)) is much less sensitive to elevated turbidity than piscivorous feeding by sablefish (Anoplopoma fimbria). Planktivorous feeding in the turbidity range tested (0–40 nephelometric turbidity units (NTU)) was reduced at high light intensity, but not at low light intensity. Comparatively low (5–10 NTU) turbidity decreased both the rate at which sablefish pursued prey and the probability of successful prey capture. These results suggest that turbid environments may be advantageous for planktivorous fish because they will be less vulnerable to predation by piscivores, but will not experience a substantial decrease in their ability to capture zooplankton prey.

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