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1

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Lack of spatial coherence of predators with prey: a bioenergetic explanation for Atlantic cod feeding on capelin (1994)

Horne, John K. ; Schneider, David C.

Oxford, UK : Blackwell Publishing Ltd

Journal of fish biology 45 (1994), S. 0

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ISSN: 1095-8649

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: We tested two biologically based predictions that potentially influence scales of spatial association between Atlantic cod, Gadus morhua, and prey populations of capelin, Mallotus vilhsus. If cod aggregate in response to concentrations of prey, then spatial association (coherence) between capelin and cod was predicted to peak at the scale of maximum capelin spatial variance. If capelin-cod coherence did not match the scale of maximum prey spatial variability, then capelin-cod coherence was predicted to peak at the spatial scale that maximizes net energetic benefit to the predator. Contrary to predictions, we found no evidence of aggregative responses of cod to capelin over resolution scales of 20 m to 10 km. This result was observed consistently at the temporal scale of a single transect (c. 1 h duration) and at the scale of averaged transects (c. 2 weeks duration). Estimates of cod foraging energetics showed that they were not constrained by physiology to aggregate relative to capelin at any scale less than 10 km. A net energetic gain of 478 to 784 kJ would result if a 44 cm, 752 g cod consumed a ration of eight to 12 capelin over a period of 58 h. Energetic calculations included costs of egestion and excretion (317 to 476 kJ), maintenance (58 kJ), digestion (125 to 188 kJ), and continuous swimming during ration assimilation (79 kJ). During this period, a 44 cm cod could travel over 38 km swimming at 1 b.l. s−1. Foraging cod are virtually certain to encounter capelin over this distance based on the abundance of pre-spawning capelin present in coastal bays during the spawning season. This study illustrates that aggregative responses of predators do no occur at all scales and possibly occur over a very limited range of scales.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1095-8649.1994.tb01093.x

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2

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Seabirds and fronts: a brief overview (1990)

SCHNEIDER, DAVID C.

Oxford, UK : Blackwell Publishing Ltd

Polar research 8 (1990), S. 0

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ISSN: 1751-8369

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Geography , Geosciences

Notes: Oceanographic fronts are the sites of enhanced physical and biological activity, including locally concentrated feeding by marine birds. Two general hypotheses relating marine birds to fronts have been developed. The first is that enhanced primary production at fronts increases prey supply through increased animal growth, reproduction, or immigration. The second is that prey patches develop at fronts either through behavioural responses of prey to thermal or salinity gradients, or through interaction between prey behaviour and circulatory patterns. Several recent studies support the second hypothesis. The first hypothesis, that birds benefit from enhanced primary production at fronts, has yet to be evaluated. We need a better understanding of trophic mechanisms at fronts in order to determine (1) the proportion of daily energy requirements extracted by predators at fronts; (2) the proportion of natural mortality of prey populations at fronts; and (3) the probability of contact between seabirds and point source pollutants.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1751-8369.1990.tb00370.x

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3

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Spatial autocorrelation in marine birds (1990)

SCHNEIDER, DAVID C.

Oxford, UK : Blackwell Publishing Ltd

Polar research 8 (1990), S. 0

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ISSN: 1751-8369

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Geography , Geosciences

Notes: All marine organisms exhibit some degree of spatial autocorrelation, which is the tendency for high (or low) densities to occur in proximity, rather than at random in the ocean. Autocorrelation occurs at scales ranging from the length of the organism to thousands of kilometres. Autocorrelation results from a wide variety of mechanisms, many of which act at characteristic scales. Consequently, some insight into causal mechanisms can be obtained from exploratory analysis of the scale and intensity of autocorrelation of abundance or behaviour, and the scale and intensity (coherence) of cross-correlation with environmental variables such as water temperature or prey abundance. This paper uses seabird counts along extended transects to illustrate standard measures of autocorrelation and cross-correlation. A brief discussion of exploratory and confirmatory analysis of autocorrelated data on marine birds follows.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1751-8369.1990.tb00379.x

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4

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The timing of spawning in capelin (Mallotus villosus Müller) at a coastal location in eastern Newfoundland (1996)

Therriault, Thomas W. ; Schneider, David C. ; Methven, David A.

Springer

Polar biology 16 (1996), S. 201-207

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ISSN: 1432-2056

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract We tested three hypotheses concerning the timing of spawning for a circumpolar species, capelin (Mallotus villosus), for which timing of larval emergence is known to be synchronized by physical conditions. The first hypothesis, developed from previous studies, was that spawning would be synchronized by upwelling events. Initial results from Middle Cove Beach in eastern Newfoundland indicated that spawning was not synchronized with upwelling. We next hypothesized that spawning was a function of several environmental variables. Results from logistic regression indicated that neither single-factor nor multi-factor models could explain the timing of spawning. Single variables could predict spawning in some years but no variable could reliably predict the time of spawning year after year. Finally, we hypothesized that the probability of spawning increased as a set of significant variables approached preferred levels. For capelin at Middle Cove, the set of variables that influence capelin spawning were identified as wave height, sea surface roughness and capelin abundance in the water. Thus only a combination of variables explained the timing of spawning for capelin. Preferred conditions for capelin spawning were wave heights less than 20 cm at the beach, a sea surface with a slight ripple, and an intermediate rank abundance of capelin in the water corresponding to hundreds to thousands of individuals. Capelin abundance alone was not a useful predictor. During the course of the study we observed a shift in the dates that capelin arrived and spawned at the beach. During 1987–1990 capelin spawned at Middle Cove Beach during June, but in more recent years (1991–1993) capelin did not arrive or spawn until July.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF02329208

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5

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The timing of spawning in capelin (Mallotus villosus Müller) at a coastal location in eastern Newfoundland (1996)

Therriault, T. W. ; Schneider, David C. ; Methven, David A.

Springer

Polar biology 16 (1996), S. 201-207

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ISSN: 1432-2056

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract We tested three hypotheses concerning the timing of spawning for a circumpolar species, capelin (Mallotus villosus), for which timing of larval emergence is known to be synchronized by physical conditions. The first hypothesis, developed from previous studies, was that spawning would be synchronized by upwelling events. Initial results from Middle Cove Beach in eastern Newfoundland indicated that spawning was not synchronized with upwelling. We next hypothesized that spawning was a function of several environmental variables. Results from logistic regression indicated that neither single-factor nor multi-factor models could explain the timing of spawning. Single variables could predict spawning in some years but no variable could reliably predict the time of spawning year after year. Finally, we hypothesized that the probability of spawning increased as a set of significant variables approached preferred levels. For capelin at Middle Cove, the set of variables that influence capelin spawning were identified as wave height, sea surface roughness and capelin abundance in the water. Thus only a combination of variables explained the timing of spawning for capelin. Preferred conditions for capelin spawning were wave heights less than 20 cm at the beach, a sea surface with a slight ripple, and an intermediate rank abundance of capelin in the water corresponding to hundreds to thousands of individuals. Capelin abundance alone was not a useful predictor. During the course of the study we observed a shift in the dates that capelin arrived and spawned at the beach. During 1987–1990 capelin spawned at Middle Cove Beach during June, but in more recent years (1991–1993) capelin did not arrive or spawn until July.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s003000050045

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6

Electronic Resource

Evaluation of a gradient sampling design for environmental impact assessment (1997)

Ellis, Joanne I. ; Schneider, David C.

Springer

Environmental monitoring and assessment 48 (1997), S. 157-172

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ISSN: 1573-2959

Keywords: BACI design ; environmental impactassessment ; power of sampling

Source: Springer Online Journal Archives 1860-2000

Topics: Energy, Environment Protection, Nuclear Power Engineering

Notes: Abstract Before-After Control Impact (BACI) sampling designsare commonly used in environmental impact assessmentand are considered the most effective for detectingchanges due to anthropogenic disturbances. Thesedesigns handle local spatial variability throughrandomized placement of samples into a treatmentstratum and a control stratum. When a contaminantdisperses with distance from a point source it issuggested that a ’gradient‘ design will be moresensitive to change than randomized placement ofsamples. This requires allocating samples according todistance, rather than by random placement withinrandomly placed blocks. In this paper gradient versusrandom sampling designs were compared using data froman oil field in the North Sea. The gradient samplingdesign was more powerful than a randomized CI sampling design.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1005752603707

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