The influence of prey availability on ontogenetic diet shifts of a juvenile piscivore

2006 ◽  
Vol 63 (8) ◽  
pp. 1722-1733 ◽  
Author(s):  
Tracy L Galarowicz ◽  
Julie A Adams ◽  
David H Wahl
Keyword(s):  
Benthic Invertebrates ◽  
Prey Availability ◽  
Juvenile Fish ◽  
Prey Type ◽  
Ontogenetic Changes ◽  
Foraging Patterns ◽  
Feeding Experiments ◽  
Ontogenetic Diet Shifts ◽  
Predator Foraging ◽  
Diet Shifts

Young-of-year piscivores typically undergo ontogenetic diet shifts from planktivory to benthivory to piscivory. These shifts are often the result of changes in predator foraging abilities, but little is known about the influence of relative prey availability. As a result, we examined diet shifts across a range of sizes (20–150 mm) of a young-of-year piscivore, walleye (Sander vitreus), in feeding experiments in which zooplankton, benthic invertebrates, and fish were made available at different density combinations. Consumption of each prey type changed with walleye size and prey densities. Small juveniles (20 mm) selected zooplankton and fish, whereas larger walleye (40–100 mm) selected benthic invertebrates and fish. Relative prey densities influenced consumption; increased densities of more profitable prey types resulted in reduced consumption of less profitable prey. Walleye larger than 100 mm selected only fish. Foraging efficiencies also varied with size and prey types; small walleye (20 mm) were less likely to pursue benthic invertebrates and retain captured fish. These ontogenetic changes in foraging patterns are linked to prey profitability, have growth consequences for juvenile walleye, and have implications for understanding diet shifts of other juvenile fish.

Foraging by a young-of-the-year piscivore: the role of predator size, prey type, and density

2005 ◽  
Vol 62 (10) ◽  
pp. 2330-2342 ◽  
Author(s):  
Tracy L Galarowicz ◽  
David H Wahl
Keyword(s):  
Benthic Invertebrates ◽  
Prey Selection ◽  
Handling Time ◽  
Prey Type ◽  
Benthic Invertebrate ◽  
Ontogenetic Changes ◽  
Functional Responses ◽  
Fish Prey ◽  
Young Of The Year ◽  
Diet Shifts

Young-of-the-year piscivores undergo ontogenetic diet shifts, but mechanisms influencing prey selection and implications for growth are unclear. We examined foraging and growth of 20- to 150-mm walleye (Sander vitreus) fed either zooplankton, benthic invertebrates, or fish over a range of prey densities in the laboratory. The number of each prey type consumed was influenced by walleye size and prey density. Walleye exhibited type II functional responses on each prey type; attack coefficients were constant across zooplankton and fish densities but decreased with benthic invertebrate densities. Handling time estimates were greater for fish than for other prey types but similar for zooplankton and benthos. Foraging efficiencies on zooplankton and benthic invertebrates increased with walleye size but were variable for fish prey. The smallest walleye size class (20 mm) had similar energy return (J·min–1) and growth (g·day–1) on zooplankton, benthic invertebrates, and fish. For larger walleye, both energy return and growth were highest on fish, intermediate on benthic invertebrates, and lowest on zooplankton. Diet shifts of juvenile piscivores and, consequently, growth can be explained by ontogenetic changes in foraging abilities and prey densities.

Larval sand lance (Ammodytes sp.) in the diet of small juvenile wolffish (Anarhichas spp.): predatory interactions in frontal water masses off western Greenland

2002 ◽  
Vol 59 (11) ◽  
pp. 1759-1767 ◽  
Author(s):  
Peter Munk
Keyword(s):  
Fish Larvae ◽  
Stomach Contents ◽  
Prey Type ◽  
Ontogenetic Changes ◽  
Sand Lance ◽  
Larval Size ◽  
Predatory Behaviour ◽  
Dietary Shift ◽  
Abundance Estimates ◽  
Anarhichas Lupus

The predatory behaviour of two species of juvenile wolffish (Anarhichas lupus and Anarhichas minor) was studied during a field campaign across a frontal area off western Greenland. The study focused on ontogenetic changes in prey-type and -size preference of the wolffish and their predatory impact on a cohabiting population of larval sand lance (Ammodytes sp.). Sampling took place along a cross-shelf transect at latitude 66°20' N, and the analysis is based on stomach contents of assembled wolffish (2–5 cm in length) and abundance estimates of plankton and fish. An ontogenetic change in wolffish prey preference was evident as a dietary shift from copepods and smaller amphipods to larger amphipods and fish larvae. The inclusion of fish larvae in the wolffish diet led to a marked increase in prey biomass, and fish larvae constituted up to 77% of diet biomass in the largest juveniles caught. Wolffish selectively targeted the smaller-sized part of the larval sand lance population; hence, larval vulnerability increased with decreasing size. Comparison between estimated predation rates and abundances of predator and prey indicated larval predation mortalities of up to 5% per day, with mortality peaking in the vicinity of a hydrographic front. Hence, findings suggest substantial predation pressure on larvae, primarily related to larval size and distribution.

Ontogenetic Niche Shifts

2013 ◽  
Author(s):  
André M. de Roos ◽  
Lennart Persson
Keyword(s):  
Life History ◽  
Extended Model ◽  
Full Model ◽  
Life History Stages ◽  
Ontogenetic Diet Shifts ◽  
Ontogenetic Niche Shifts ◽  
Niche Shifts ◽  
Limited Supply ◽  
Diet Shifts ◽  
Parameter Values

This chapter considers the consequences for community structure of ontogenetic diet shifts that involve the use of different resources in different life history stages, whereby these resources are in limited supply and are hence competed for by all individuals foraging on them. It explores the consequences of ontogenetic diet shifts using stage-structured biomass models that account for two basic resources, a stage-structured consumer population, for which we distinguish between juveniles and adults, and up to two unstructured predator populations. The most extended model is therefore closely related to the model analyzed in Chapter 5, except for the inclusion of an additional basic resource. The equations of the full model are summarized and default parameter values are listed.

Size-selective predation by river otter (Lontra canadensis) improves refuge properties of shallow coastal marine nursery habitats

2008 ◽  
Vol 86 (11) ◽  
pp. 1324-1328 ◽  
Author(s):  
D. Cote ◽  
R. S. Gregory ◽  
H. M.J. Stewart
Keyword(s):  
Shallow Water ◽  
Atlantic Cod ◽  
Prey Availability ◽  
Juvenile Fish ◽  
Lontra Canadensis ◽  
River Otter ◽  
Fish Nursery ◽  
Piscivorous Fish ◽  
Risk Of Predation ◽  
Nursery Habitats

Young fish often avoid deep water to reduce predation risk from larger fish. Less clear are explanations for the avoidance of shallows by large piscivorous fish; however, one hypothesis suggests that this distribution reduces contact with depth-limited semi-aquatic mammal and bird piscivores. We determined prey size selection of the river otter ( Lontra canadensis (Schreber, 1777)) to test the hypothesis that larger fish are at elevated risk in shallow coastal waters in Newman Sound, Newfoundland, during June–November 2001 and May 2002. We compared otter diet (scat analysis) and prey availability (seine sampling) to test this hypothesis. Five fish taxa (Atlantic cod ( Gadus morhua L., 1758), Greenland cod ( Gadus ogac Richardson, 1836), shorthorn sculpin ( Myoxocephalus scorpius (L., 1758)), cunner ( Tautogolabrus adspersus (Walbaum, 1792)), and winter flounder ( Pseudopleuronectes americanus (Walbaum, 1792))) dominated the shallow-water fish community and were sufficiently abundant in otter scats to examine feeding preferences. Larger, piscivorous fish were selected by otters, suggesting that they were at greater risk of predation than smaller fish, consistent with our hypothesis that depth-limited, diurnally active predators restrict large fish from hunting in shallow water during daytime. We suggest that depth-limited air-breathing predators may reduce the presence of such predatory fish in shallow-water juvenile fish nursery habitats.

Variation in the diet of the Lataste's viper Vipera latastei in the Iberian Peninsula: seasonal, sexual and size-related effects

2007 ◽  
Vol 57 (1) ◽  
pp. 49-61 ◽  
Author(s):  
Juan Pleguezuelos ◽  
José Brito ◽  
Soumia Fahd ◽  
Xavier Santos ◽  
Gustavo Llorente ◽  
...  
Keyword(s):  
Iberian Peninsula ◽  
Conservation Management ◽  
Prey Availability ◽  
Feeding Activity ◽  
Prey Type ◽  
Ontogenetic Shift ◽  
Ecological Data ◽  
Opposite Pattern ◽  
Iberian Range ◽  
Ambush Predation

AbstractSeveral life-history traits may increase vulnerability of species to extinction. Among snakes, ambush predation and dietary specialisation are factors that increase this vulnerability. European viper species, genus Vipera, display such traits and are categorised as endangered in several parts of its range. For their conservation management, a deeper knowledge of their ecology and habitat use is highly relevant. One of the species with less ecological data is the Lataste's viper Vipera latastei, a species which lives in the Iberian Peninsula and northwestern Africa. Here, we describe its diet based on the analysis of gut content of 435 museum specimens plus nine bibliographic data from the entire Iberian range. The species showed seasonal and ontogenetic shift in diet but no sexual variations. Feeding activity (percentage of vipers with prey) was low in accordance with its ambush predation tactics, being lower in spring than in summer and autumn. Prey spectrum included two main (reptiles and small mammals), and three sporadic, types of prey (arthropods, amphibians and birds). The consumption of reptiles and mammals was seasonal; the former decreased in occurrence from spring to autumn, whereas the latter showed an opposite pattern. There was an ontogenetic shift in the diet: juveniles fed mainly on reptiles and arthropods, whereas adult vipers progressively substitute this prey with insectivores, and the largest vipers primarily foraged on rodents and birds. Our results suggest that the seasonal variation in prey type was related to prey availability, whereas the ontogenetic shift was linked to gape limitation. The apparently wide prey spectrum of V. latastei must therefore be examined, taking into account that there are seasonal and ontogenetic dietary variations as well as geographic differences, the latter probably driven by climatic contrasts into the Iberian Peninsula. This new data of the endangered Iberian V. latastei can aid the effective conservation management of this species.

scholarly journals Fine-scale dietary changes between the breeding and non-breeding diet of a resident seabird

2015 ◽  
Vol 2 (4) ◽  
pp. 140291 ◽  
Author(s):  
Nicole D. Kowalczyk ◽  
André Chiaradia ◽  
Tiana J. Preston ◽  
Richard D. Reina
Keyword(s):  
Prey Availability ◽  
Juvenile Fish ◽  
Fish Communities ◽  
Small Range ◽  
Isotopic Niche ◽  
Fine Scale ◽  
Close Proximity ◽  
Isotope Analyses ◽  
Little Penguin ◽  
Foraging Ranges

Unlike migratory seabirds with wide foraging ranges, resident seabirds forage in a relatively small range year-round and are thus particularly vulnerable to local shifts in prey availability. In order to manage their populations effectively, it is necessary to identify their key prey across and within years. Here, stomach content and stable isotope analyses were used to reconstruct the diet and isotopic niche of the little penguin ( Eudyptula minor ). Across years, the diet of penguins was dominated by anchovy ( Engraulis australis ). Within years, during winter, penguins were consistently enriched in δ 15 N and δ 13 C levels relative to pre-moult penguins. This was probably due to their increased reliance on juvenile anchovies, which dominate prey biomass in winter months. Following winter and during breeding, the δ 13 C values of penguins declined. We suggest this subtle shift was in response to the increased consumption of prey that enter the bay from offshore regions to spawn. Our findings highlight that penguins have access to both juvenile fish communities and spawning migrants across the year, enabling these seabirds to remain in close proximity to their colony. However, annual fluctuations in penguin isotopic niche suggest that the recruitment success and abundance of fish communities fluctuate dramatically between years. As such, the continued monitoring of penguin diet will be central to their ongoing management.

The diet of Antechinus agilis and A. swainsonii in unlogged and regenerating sites in Mumbulla State Forest, south-eastern New South Wales

2001 ◽  
Vol 28 (5) ◽  
pp. 459 ◽  
Author(s):  
Daniel Lunney ◽  
Alison Matthews ◽  
Jan Grigg
Keyword(s):  
Prey Availability ◽  
Age Classes ◽  
Foraging Patterns ◽  
Terrestrial Invertebrates ◽  
Egg Capsules ◽  
Interspecific Differences ◽  
South Wales ◽  
Lepidopteran Larvae ◽  
Logged Forest ◽  
Antechinus Agilis

Analyses of the diets of Antechinus agilis and A. swainsonii from Mumbulla State Forest examined possible differences between species, sexes, logging treatment and aspect. Taxa from 15 orders were identified in the diet, and were predominantly terrestrial invertebrates. Overall, the dietary components were similar for each species, but the frequencies taken showed some differences. A. swainsonii ate more Diplopoda, Chilopoda and Blattodea egg capsules, while A. agilis ate more weevils (Coleoptera: Curculionidae). Male A. agilis ate more coleopteran larvae, while females ate more Araneae. This difference in Araneae in the diet between sexes of A. agilis was significant in logged forest but not in unlogged forest. Female A. swainsonii ate more Isoptera than did males. The frequency of occurrence of lepidopteran larvae taken by A. agilis differed across the three age-classes of forest, with more taken in 26–34-year-old regrowth forest and none in unlogged forest. Vertebrate remains – small skinks (Lampropholis spp.) and feathertail glider (Acrobates pygmaeus) – were found only in A. agilis; these occurred infrequently in the diet. These interspecific differences, sex differences and, most importantly, differences between age classes of forest warrant further investigation, particularly those relating to foraging patterns and prey availability.

scholarly journals A Review of Galaxias (Galaxiidae) Fossils from the Southern Hemisphere

Diversity ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 208
Author(s):  
Uwe Kaulfuss ◽  
Daphne E. Lee ◽  
Jeffrey H. Robinson ◽  
Graham P. Wallis ◽  
Werner W. Schwarzhans
Keyword(s):  
New Zealand ◽  
Southern Hemisphere ◽  
Fossil Record ◽  
New Caledonia ◽  
Adult Fish ◽  
Gut Content ◽  
Ontogenetic Diet Shifts ◽  
Subantarctic Islands ◽  
Diet Shifts

The Galaxiidae is a Southern Hemisphere family of freshwater fish, considered to be of Gondwanan origin based on the current distribution of species in New Zealand, Australia (including Tasmania), New Caledonia, Africa, South America, and on some associated and subantarctic islands. The fossil record of galaxiids is extremely sparse and geographically restricted. The only galaxiid fossils currently known come from several Miocene lakes in southern New Zealand. They include more than 100 articulated fishes, some remarkably preserving soft parts such as eyes and skin, skulls and jaw components, and more than 200 isolated otoliths. Common coprolites and in situ preserved gut content at one site (Foulden Maar) indicate the different diets of larvae and adult fish. These discoveries reveal a diverse Galaxias fauna, the presence of lake-locked populations, ontogenetic diet shifts, and representatives of several non-migratory Galaxias lineages associated with inland streams and lakes. There are at least six Galaxias species based on macrofossils and six separate otolith-based species from varied volcanic and regional lacustrine environments. This diversity points to southern New Zealand as a centre of biodiversity and speciation in Galaxiidae in the early to late Miocene.

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