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 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 Long-term changes in kelp forests in an inner basin of the Salish Sea

PLoS ONE ◽  
2021 ◽  
Vol 16 (2) ◽  
pp. e0229703
Author(s):  
Helen D. Berry ◽  
Thomas F. Mumford ◽  
Bart Christiaen ◽  
Pete Dowty ◽  
Max Calloway ◽  
...  
Keyword(s):  
Puget Sound ◽  
Environmental Stressors ◽  
Nutrient Concentrations ◽  
Kelp Forests ◽  
High Current ◽  
Salish Sea ◽  
Climate Conditions ◽  
Kelp Beds ◽  
Biogenic Habitat

Kelp forests form an important biogenic habitat that responds to natural and human drivers. Global concerns exist about threats to kelp forests, yet long-term information is limited and research suggests that trends are geographically distinct. We examined distribution of the bull kelp Nereocystis luetkeana over 145 years in South Puget Sound (SPS), a semi-protected inner basin in a fjord estuary complex in the northeast Pacific Ocean. We synthesized 48 historical and modern Nereocystis surveys and examined presence/absence within 1-km segments along 452 km of shoreline. Compared to the earliest baseline in 1878, Nereocystis extent in 2017 decreased 63%, with individual sub-basins showing up to 96% loss. Losses have persisted for decades, across a range of climate conditions. In recent decades, Nereocystis predominantly occurred along shorelines with intense currents and mixing, where temperature and nutrient concentrations did not reach thresholds for impacts to Nereocystis performance, and high current speeds likely excluded grazers. Losses predominated in areas with elevated temperature, lower nutrient concentrations, and relatively low current velocities. The pattern of long-term losses in SPS contrasts with stability in floating kelp abundance during the last century in an area of the Salish Sea with greater wave exposure and proximity to oceanic conditions. These findings support the hypothesis that kelp beds along wave-sheltered shorelines exhibit greater sensitivity to environmental stressors. Additionally, shorelines with strong currents and deep-water mixing may provide refugia within sheltered systems.

Probable Error in Pig-Feeding Trials

1915 ◽  
Vol 7 (2) ◽  
pp. 137-141
Author(s):  
Charles Crowther
Keyword(s):  
Statistical Analysis ◽  
Live Weight ◽  
Probable Error ◽  
Weight Increase ◽  
Feeding Experiment ◽  
Feeding Experiments ◽  
Feeding Trials

In an earlier issue of this Journal, Robinson and Halnan have communicated the results of a statistical analysis of three sets of pig-feeding experiments from which they conclude that “the probable error of one animal in a pig-feeding experiment is in the region of 10 per cent, of the average live-weight increase.”

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.

scholarly journals Time-since-invasion increases native mesoherbivore feeding rates on the invasive alga, Sargassum muticum (Yendo) Fensholt

2017 ◽  
Vol 98 (8) ◽  
pp. 1935-1944 ◽  
Author(s):  
Martyn Kurr ◽  
Andrew J. Davies
Keyword(s):  
Invasive Plants ◽  
Enemy Release Hypothesis ◽  
Sargassum Muticum ◽  
Enemy Release ◽  
Feeding Rates ◽  
Herbivore Species ◽  
Feeding Trials ◽  
Negative Impacts ◽  
Abundance And Diversity ◽  
Invasive Alga

Invasive algae can have substantial negative impacts in their invaded ranges. One widely cited mechanism that attempts to explain how invasive plants and algae are often able to spread quickly, and even become dominant in their invaded ranges, is the Enemy Release Hypothesis. This study assessed the feeding behaviours of two species of gastropod herbivore from populations exposed to the invasive alga Sargassum muticum for different lengths of time. Feeding trials, consisting of both choice and no-choice, showed that the herbivores from older stands (35–40 years established) of S. muticum were more likely to feed upon it than those taken from younger (10–19 years established) stands. These findings provide evidence in support of the ERH, by showing that herbivores consumed less S. muticum if they were not experienced with it. These findings are in accordance with the results of other feeding-trials with S. muticum, but in contrast to research that utilizes observations of herbivore abundance and diversity to assess top-down pressure. The former tend to validate the ERH, and the latter typically reject it. The potential causes of this disparity are discussed, as are the importance of palatability, herbivore species and time-since-invasion when considering research into the ERH. This study takes an important, yet neglected, approach to the study of invasive ecology.

Influence of Early Lactation Assistance on Inpatient Exclusive Breastfeeding Rates

2020 ◽  
pp. 089033442095796
Author(s):  
Keyaria D. Gray ◽  
Emily A. Hannon ◽  
Elizabeth Erickson ◽  
Ariana B. Stewart ◽  
Charles T. Wood ◽  
...  
Keyword(s):  
Human Milk ◽  
Private Insurance ◽  
Feeding Preference ◽  
Feeding Rates ◽  
Term Infants ◽  
Lactation Consultant ◽  
Childhood Illnesses ◽  
Healthy Infants ◽  
Birth Hospitalization ◽  
Milk Feeding

Background Human milk feeding reduces the incidence and costs of several maternal and childhood illnesses. Initiation and success of human milk feeding are influenced by race, socioeconomic status, and family support. The influence of early in-hospital lactation assistance in breastfeeding success has been not well described. Research aims We aimed to determine how suspected known factors influencing breastfeeding success influence in-hospital human milk feeding rates. Second, we aimed to examine how timing of lactation assistance is related to success of human milk feeding during the newborn hospitalization for healthy infants. Methods We conducted a retrospective cohort study of term infants born between January 1, 2014 and December 31, 2016 at a large tertiary academic hospital. We considered “success” to be 100% human milk feeding during the birth hospitalization, and compared differences in success by demographics, payor, race, and initial feeding preference. Influences of lactation assistance on success were analyzed using multivariable logistic regression. Results Mean success with exclusive human milk feeding among 7,370 infants was 48.9%, ( n = 3,601). Successful participants were more likely to be 39–40 weeks’ gestation (64.9%, n = 2,340), non-Hispanic/non-Latino (80.0%, n = 2,882), and using private insurance (69.2%, n = 2,491). Participants who had early feeding assisted by an International Board Certified Lactation Consultant (IBCLC) before being fed any formula were more likely to be successful than participants who had a feeding assisted by a non-IBCLC nurse (80% vs. 40% respectively). Conclusions Success for exclusive human milk feeding during newborn hospitalization is strongly associated with several factors. Early intervention with IBCLCs can greatly improve breastfeeding success.

An improved method of diet preparation for toxicological feeding experiments

1984 ◽  
Vol 18 (3) ◽  
pp. 271-274 ◽  
Author(s):  
R. E. Morrissey ◽  
W. P. Norred
Keyword(s):  
Dietary Treatment ◽  
Feeding Preference ◽  
Feed Consumption ◽  
Distilled Water ◽  
Feed Conversion ◽  
Preparation Time ◽  
Treatment Groups ◽  
Feeding Experiments ◽  
Freeze Dried ◽  
Animal Feeding

Groups of 30 rats each were fed 1 of 4 diets to determine feeding preference for freeze-dried meal compared to dry meal, and to determine if 3% agar is a desirable component of freeze-dried meal. The diets were: dry meal, meal+distilled water(freeze-dried), meal+3% agar in distilled water(freeze-dried), and meal+3% agar in distilled water(gel). Diet preparation, and the method for introducing a toxin in a toxicological study, is described. Feed consumption, bodyweight, and observational data were collected. Rats ate freeze-dried meal in amounts comparable to dry meal. There were no significant variations in feed conversion ratios among the dietary treatment groups. Agar is not required for freeze-dried diets, and we recommend that it be omitted to save resources and preparation time. Freeze-dried diets have a longer storage and cage life, thus the frequency of diet preparation, animal feeding and dean-up arc reduced. For studies involving a toxin, these factors would reduce the potential for accidental exposure of personnel to potentially harmful materials.

Fattening studies with cross-bred (European×Zebu) bulls: 1. Performance on diets of native hay and concentrate

1978 ◽  
Vol 90 (2) ◽  
pp. 425-429 ◽  
Author(s):  
P. B. O'Donovan ◽  
A. Gebrewolde ◽  
B. Kebede ◽  
E. S. E. Galal
Keyword(s):  
Weight Gain ◽  
Feed Intake ◽  
Live Weight ◽  
Maximum Temperature ◽  
Research Station ◽  
Live Weight Gain ◽  
The Third ◽  
Feeding Experiments ◽  
Group Feeding ◽  
Feeding Trials

SummaryTwo group-feeding and one individual-feeding experiments were made for 112 and 182 days, respectively, with 76 cross-bred and eight Zebu bulls. Simmental, Friesian and Jersey sire breeds were mated to three Ethiopian Zebu breeds, namely Boran, Horro and Barca, while Zebu bulls were included for comparison purposes in Expt 3. The trials were conducted in confinement at Holetta Research Station, located at 2400 m elevation and having a mean maximum temperature range of 18·7–24 °C. In the group-feeding trials (Expts 1 and 2) a common diet was fed, consisting of native hay (30%) molasses (20%) and a concentrate supplement. In the third experiment, two diets containing 30 and 50% native hay were supplemented by concentrate and fed individually to eight Simmental and eight Friesian cross bulls, while eight Zebus served as a control.The average daily gains, feed intake and conversion did not differ markedly between Simmental and Friesian crosses, but lower values were generally found for Jersey crosses. Cross-breds outgained Zebus, consumed more feed and converted it more efficiently to live-weight gain. Performance differences were noted between the Zebu breeds as well as some evidence of sire × dam breed interactions. Significantly higher gains were achieved with the low than with the high roughage diet.

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 Diverse traits of aquatic plants cannot individually explain their consumption by the generalist gastropod Biomphalairia glabrata

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e12031
Author(s):  
Renato Crespo Pereira ◽  
Nathália Nocchi ◽  
Tatiana U.P. Konno ◽  
Angelica R. Soares
Keyword(s):  
Aquatic Plants ◽  
Defense Mechanism ◽  
Experimental Studies ◽  
Biomphalaria Glabrata ◽  
Life Forms ◽  
Dry Mass ◽  
Feeding Preference ◽  
Feeding Experiments ◽  
Chemical Traits ◽  
The Relationship

Several experimental studies on aquatic plants have reported the prevalence of chemical defense mechanism against herbivory, as opposed to structural, life-forms or other traits. Here, our laboratory feeding experiments and integrative analysis explored the relationship among palatability (fresh or reconstituted plants used as artificial diet) and various chemical/nutritional traits (i.e., contents of dry mass, ash, nitrogen, protein, and phenols) of diverse aquatic plants and their susceptibility to consumption by the generalist gastropod Biomphalaria glabrata. Biomphalaria glabrata consumed all of the assayed aquatic plants in a hierarchical yet generalized way, with the consumption of fresh plants, their reconstituted forms and defensive properties of lipophilic extracts not being significantly correlated with plant physical or chemical traits to determine the feeding preference of the gastropod. Our results do not reveal a prevalence for a specific plant attribute contributing to herbivory. Instead, they indicate that the susceptibility of aquatic plants to generalist consumers is probably related to a combination of their chemical and physical properties, resulting in moderate grazing rates by generalist consumers.

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