Estimation of Functional Responses of Predators on Juvenile Salmon

1978 ◽  
Vol 35 (6) ◽  
pp. 797-808 ◽  
Author(s):  
Randall M. Peterman ◽  
Marino Gatto
Keyword(s):  
Functional Response ◽  
Chum Salmon ◽  
Pink Salmon ◽  
Experimental Studies ◽  
Functional Responses ◽  
Response Curves ◽  
Response Component ◽  
Predation Mortality ◽  
Salmon Fry ◽  
Salmon Population

Several studies have shown that predators can eat large portions (up to 85%) of emerging salmon (Oncorhynchus spp.) fry populations. To understand salmon population dynamics and the effect of salmon enhancement projects, it is necessary to determine how present predation mortality varies with prey density. To predict the shape of this relation outside the range of past observations, we must examine the basic components of the predation process, the functional and numerical responses. A review of past, sparse data on the functional response component shows that predators of salmon fry and smolts were mostly not being saturated (i.e. maximum attack rates were not being achieved) at high prey densities. A method to estimate functional responses from certain types of existing field data is derived and applied to Hooknose Creek pink salmon (O. gorbuscha) and chum salmon (O. keta) information. Results from 7 out of 9 yr corroborate earlier observations that predators are normally operating on the low end of their functional response curves and are therefore capable of causing high mortality on larger prey populations. Also, competition among predators is demonstrated to be significant, resulting in changes in slopes of functional responses. More experimental studies of functional responses are needed, and such research should be carried out in conjunction with perturbations in salmon fry abundance which will result from enhancement projects. Key words: salmon fry, predation, freshwater survival, enhancement, functional response, predator competition

Predator-dependent functional responses and interaction strengths in a natural food web

2004 ◽  
Vol 61 (11) ◽  
pp. 2215-2226 ◽  
Author(s):  
Timothy E Essington ◽  
Sture Hansson
Keyword(s):  
Food Webs ◽  
Functional Response ◽  
Gadus Morhua ◽  
Prey Species ◽  
Clupea Harengus ◽  
Natural Food ◽  
Functional Responses ◽  
Predation Mortality ◽  
Highly Sensitive ◽  
Predator Abundance

Predator-dependent functional responses decouple predation mortality from fluctuations in predator abundance and therefore can prevent strong "top-down" interaction strengths in food webs. We evaluated whether contrasts in the functional response of Baltic Sea cod (Gadus morhua) were consistent with the contrasting population dynamics of two prey species, herring (Clupea harengus) and sprat (Sprattus sprattus): sprat abundance increased nearly threefold following a sharp decline in the cod population (a strong interaction), whereas herring abundance failed to increase (a weak interaction). We found striking differences in the functional response of cod on alternative prey, and these were consistent with the observed patterns in interaction strengths. Cod predation was the dominant source of mortality for age-1 and age-2 sprat but was only important for age-1 herring. Moreover, the magnitude of predation mortality on age-1 and age-2 sprat was highly sensitive to cod biomass, whereas predation mortality on herring was only moderately sensitive to cod biomass. These analyses suggest the possibility that food webs are comprised of linkages that vary with respect to the magnitude and importance of predation mortality and how this mortality varies with changes in predator abundance.

Reactions of Juvenile Pacific Salmon to Light

1957 ◽  
Vol 14 (6) ◽  
pp. 815-830 ◽  
Author(s):  
W. S. Hoar ◽  
M. H. A. Keenleyside ◽  
R. G. Goodall
Keyword(s):  
Chum Salmon ◽  
Pacific Salmon ◽  
Pink Salmon ◽  
Low Light ◽  
Salmon Fry ◽  
Experimental Apparatus ◽  
Schooling Behaviour ◽  
Marked Preference ◽  
Juvenile Pacific Salmon ◽  
Changing Light

When given a choice between light and dark areas, schools of chum or pink salmon fry remain in the light, sockeye fry prefer the dark and coho fry show no marked preference for either. Newly emerged sockeye fry are the most strongly photonegative, remaining mostly under stones. Older sockeye fry move more into the light. Sockeye and coho smolts stay in the dark more than sockeye and coho underyearlings. Territorial and "escape" behaviour by fish in the experimental apparatus may obscure these reactions to light. Soon after emerging from the gravel, pink fry swim near the surface under low light intensity and retreat to deeper water in brighter light. Older pink fry seem indifferent to changing light. Recently emerged chum salmon fry do not respond in this way to changing illumination, although older fry tend to swim closer to the surface. This difference between pink and chum salmon fry may be related to differences in schooling behaviour and alarm responses of the two species.

scholarly journals Holling meets habitat selection: functional response of large herbivores revisited

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Claudia Dupke ◽  
Anne Peters ◽  
Nicolas Morellet ◽  
Marco Heurich
Keyword(s):  
Habitat Selection ◽  
Land Cover ◽  
Functional Response ◽  
Discrete Choice Models ◽  
Time Of Day ◽  
Functional Responses ◽  
Response Curves ◽  
Large Herbivores ◽  
Land Cover Types ◽  
Selection Of

Abstract Background Holling (Can Entomol 91(5):293–320, 1959) was the first to describe a functional response between a predator’s consumption-rate and the density of its prey. The same concept can be applied to the habitat selection of herbivores, specifically, the change in relative habitat use with the change in habitat availability. Functional responses in habitat selection at a home-range scale have been reported for several large herbivores. However, a link to Holling’s original functional response types has never been drawn, although it could replace the current phenomenological view with a more mechanistically based understanding of functional responses. Methods In this study, discrete choice models were implemented as mixed-effects baseline-category logit models to analyze the variation in habitat selection of a large herbivore at seasonal and diurnal scales. Thus, changes in the use of land cover types with respect to their availability were investigated by monitoring 11 land cover types commonly used by roe deer (Capreolus capreolus) in the Bavarian Forest National Park, Germany. Functional response curves were then fitted using Holling’s formulas. Results Strong evidence of non-linear functional responses was obtained for almost all of the examined land cover types. The shape of the functional response curves varied depending on the season, the time of day, and in some cases between sexes. These responses could be referenced to Holling’s types, with a predominance of type II. Conclusions Our results indicate that Holling’s types can be applied to describe general patterns of the habitat selection behavior of herbivores. Functional responses in habitat selection may occur in situations requiring a trade-off in the selection of land cover types offering different resources, such as due to the temporally varying physiological needs of herbivores. Moreover, two associated parameters defining the curves (prey density and predation rate) can aid in the identification of temporal variations and in determinations of the strength of the cost-benefit ratio for a specific land cover type. Application of our novel approach, using Holling’s equations to describe functional responses in the habitat selection of herbivores, will allow the assignment of general land cover attraction values, independent of availability, thus facilitating the identification of suitable habitats.

The Behaviour of Migrating Pink and Chum Salmon Fry

1956 ◽  
Vol 13 (3) ◽  
pp. 309-325 ◽  
Author(s):  
William S. Hoar
Keyword(s):  
Light Intensity ◽  
Chum Salmon ◽  
Pink Salmon ◽  
Bright Light ◽  
Circular Channel ◽  
Water Currents ◽  
Salmon Fry ◽  
First Time

Pink salmon fry which have never schooled are negatively phototactic, prefer a cover of stones and do not emerge into bright light. Those which have schooled show a strong cover reaction when exposed to a rapid increase in light intensity but do not seek cover unless the change is abrupt. In general they remain in bright light after they have schooled. This change in behaviour occurs rapidly (15 minutes or less) when the fry school for the first time. Chum salmon fry establish a definite direction of swimming in the quiet water of a circular channel or basin. The established direction is stable and not permanently disturbed by light or darkness, by water currents, by strong avoiding reactions, by changing the location or by excluding direct skylight. The direction may be initially established in relation to water currents.

THE COMPARATIVE STUDY OF FUNCTIONAL RESPONSES: EXPERIMENTAL DESIGN AND STATISTICAL INTERPRETATION

1985 ◽  
Vol 117 (5) ◽  
pp. 617-629 ◽  
Author(s):  
Marilyn A. Houck ◽  
Richard E. Strauss
Keyword(s):  
Experimental Design ◽  
Functional Response ◽  
Maximum Likelihood Method ◽  
Graphical Method ◽  
Predation Rate ◽  
Likelihood Method ◽  
Statistical Interpretation ◽  
Functional Responses ◽  
Response Curves ◽  
The Comparative Study

AbstractMathematical discussions of models of functional response (predation rate as a function of prey density) have usually emphasized description of the shape of the functional-response curve. However, lack of congruence between experimental design and data analysis and under-utilization of appropriate statistical methods of analysis have hindered an empirical synthetic treatment of such feeding behavior. Here we review existing experimental and statistical procedures with reference to Holling's generalized model of functional response, and describe: (1) an experimental design compatible with the assumptions of the model; (2) a maximum-likelihood method for fitting the model; (3) several methods for statistical comparison of sets of functional-response curves; and (4) an exploratory graphical method for examining patterns of variation among larger numbers of samples.

Notes on the Seaward Migration of Pink and Chum Salmon Fry

1955 ◽  
Vol 12 (3) ◽  
pp. 369-374 ◽  
Author(s):  
Ferris Neave
Keyword(s):  
Vertical Distribution ◽  
Chum Salmon ◽  
Pink Salmon ◽  
Strong Light ◽  
Salmon Fry ◽  
Seaward Migration ◽  
Schooling Behaviour ◽  
And Migration ◽  
A Current ◽  
Downstream Movement

The seaward migration of pink and chum salmon fry takes place at night. Strong light is avoided. In pink salmon negative rheotaxis (swimming with a current) is strongly developed and migration is not primarily effected by random swimming and passive displacement. Downstream movement is mainly at or close to the surface. In slack water vertical distribution is more uniform. In the shortest streams examined, each night's migrants appeared to reach the sea before daybreak. In a longer stream, fry were seen to bury themselves at the onset of daylight. After being held in fresh water for an undetermined period, fry show positive rheotaxis and schooling behaviour and no longer avoid light. Behaviour of fry after reaching the sea also differs from that shown during actual migration. Changes in behaviour may coincide with commencement of feeding.

THE THYROID GLAND IN RELATION TO THE SEAWARD MIGRATION OF PACIFIC SALMON

1950 ◽  
Vol 28d (3) ◽  
pp. 126-136 ◽  
Author(s):  
William S. Hoar ◽  
G. Mary Bell
Keyword(s):  
Fresh Water ◽  
Chum Salmon ◽  
Pacific Salmon ◽  
Pink Salmon ◽  
River Estuary ◽  
Salt Balance ◽  
Thyroid Activity ◽  
Salmon Fry ◽  
Thyroid Glands ◽  
Seaward Migration

Histological examination of the thyroid glands from chum salmon fry taken in the river, estuary, or sea shows the organ to be in a quiescent condition at the time of migration. If, however, this species is retained in fresh water for two or three months the gland becomes extremely hyperplastic. The pink salmon thyroid behaves in essentially the same way as that of the chum, but migrating pink fry taken at great distances from the sea have active glands. The thyroids of yearling coho and sockeye moving into the sea display heightened activity. Thyroid activity is apparently greater in coho migrants taken later in the season from the headwaters of rivers. In part, the heightened thyroid activity seen in these migrating Pacific salmon is probably a spring-time seasonal change. It seems, however, to be more particularly related to the increased metabolic work of osmotic regulation and salt balance in a fish physiologically prepared for life in the sea. In general, this study suggests that the increased thyroid activity seen in young migrating salmonoids is largely due to increased demands for thyroid hormone in the metabolism of a fish no longer completely adjusted physiologically to fresh water.

Experimental studies on acarine predator–prey interactions: the effects of predator density on prey consumption, predator searching efficiency, and the functional response to prey density (Acarina: Phytoseiidae)

1982 ◽  
Vol 60 (4) ◽  
pp. 611-629 ◽  
Author(s):  
Eldon S. Eveleigh ◽  
D. A. Chant
Keyword(s):  
Functional Response ◽  
Adult Female ◽  
Experimental Studies ◽  
Phytoseiulus Persimilis ◽  
Predator Density ◽  
Response Curves ◽  
Phytoseiid Mites ◽  
Predator Prey ◽  
The Individual ◽  
Predation Rates

Experiments on the responses of two species of predacious phytoseiid mites, Phytoseiulus persimilis and Amblyseius degenerans, to their own density revealed that, with the exception of adult female P. persimilis, the individual predation rates of all instars of both species increased as predator and prey densities were increased within certain fixed predator to prey ratios. "Interference" between adult female P. persimilis was suggested as a possible reason for this result, and this was confirmed by the application of Hassell and Varley's model to data from an experiment where predator density was increased within various prey densities. Interference did not influence the predation rates for other instars of either species and other factors are considered to account for the results obtained.Increasing predator density caused the functional response of all instars of both species to increase over an increasingly wider range of prey densities. However, due to interference between adult female P. persimilis the functional response curves increased curvilinearly and reached plateaux at progressively lower levels of prey killed per predator as predator density increased. With the other instars of both species the responses became less curvilinear with increasing predator density, and trends in the data suggested that plateaux would be reached at similar levels of prey killed for different predator densities provided sufficient prey are present.

Experimental studies on acarine predator–prey interactions: effects of predator age and feeding history on prey consumption and the functional response (Acarina: Phytoseiidae)

1981 ◽  
Vol 59 (7) ◽  
pp. 1387-1406 ◽  
Author(s):  
Eldon S. Eveleigh ◽  
D. A. Chant
Keyword(s):  
Functional Response ◽  
Prey Density ◽  
Laboratory Experiments ◽  
Prolonged Exposure ◽  
Experimental Studies ◽  
Phytoseiulus Persimilis ◽  
Functional Responses ◽  
Phytoseiid Mites ◽  
Predatory Behaviour ◽  
Predator Prey

Laboratory experiments were performed to determine the functional response to prey density of various instars of two species of predacious phytoseiid mites, Phytoseiulus persimilis and Amblyseius degenerans, and to examine the effects of predator age and nutritional history on their responses. The experiments showed that the nutritional requirements of the predators, the time that they are exposed to prey in relation to their life-span, increasing age, and differences in nutritional history, can have important effects on predatory behaviour and the functional response. Prolonged exposure to one density of prey can cause lags in predation rates when the prey density is changed. The results indicated that functional responses are probably multiform in certain predators and the above factors may provide an explanation of the variety of responses previously reported for species of phytoseiid mites. Phytoseiulus persimilis appeared to be more sensitive to some of these factors than A. degenerans and was shown to be different in many aspects of its predatory behaviour.

Comparison of Functional Response and Mutual Interference Between Two Aphelinid Parasitoids of Bemisia argentifolii (Homoptera: Aleyrodidae)

2001 ◽  
Vol 36 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Shoil M. Greenberg ◽  
Benjamin C. Legaspi ◽  
Walker A. Jones
Keyword(s):  
Functional Response ◽  
Handling Time ◽  
Mass Rearing ◽  
Mutual Interference ◽  
Host Feeding ◽  
Bemisia Argentifolii ◽  
Functional Responses ◽  
Response Curves ◽  
Eretmocerus Mundus ◽  
Type Ii Functional Response

Functional responses and mutual interference were compared in an indigenous parasitoid, Encarsia pergandiella Howard (Hymenoptera: Aphelinidae), with that of an exotic parasitoid, Eretmocerus mundus Mercet (Aphelinidae) from Spain, attacking the silverleaf whitefly, Bemisia argentifolii Bellows and Perring (Homoptera: Aleyrodidae). Type II functional response curves were fitted to the data and were used to calculate handling time. Eretmocerus mundus attacked more whitefly nymphs than E. pergandiella. Handling times estimated from the functional responses were 72 min for E. pergandiella and 12 min for E. mundus, suggesting that lower attack rates for the former parasitoid may be attributed to longer handling times. The statistically estimated handling time for E. mundus was compared with an estimate derived from empirical observations of parasitoid behavior. Actual observations of handling time, defined as oviposition, host feeding and associated preening, yielded a mean handling time of <2 min, suggesting that functional response experiments may not produce reliable estimates of handling time. The mutual interference coefficient m of E. mundus was numerically higher than that for E. pergandiella (0.238 vs 0.184, respectively). Although there were no significant differences in m, the comparison raises the interesting question of whether parasitoids with higher attack rates may also have higher levels of mutual interference under conditions of high parasitoid density (e.g., mass rearing).

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