Variability in the growth, feeding and condition of barramundi (Lates calcarifer Bloch) in a northern Australian coastal river and impoundment

2015 ◽  
Vol 66 (10) ◽  
pp. 928 ◽  
Author(s):  
D. J. Russell ◽  
F. E. Thomson ◽  
P. A. Thuesen ◽  
T. N. Power ◽  
R. J. Mayer
Keyword(s):  
Prey Species ◽  
Prey Availability ◽  
Juvenile Fish ◽  
Fish Growth ◽  
Lates Calcarifer ◽  
Resource Limited ◽  
Tropical Australia ◽  
Coastal River ◽  
Freshwater River ◽  
River Fish

Lates calcarifer supports important fisheries throughout tropical Australia. Community-driven fish stocking has resulted in the creation of impoundment fisheries and supplemental stocking of selected wild riverine populations. Using predominantly tag–recapture methods, condition assessment and stomach flushing techniques, this study compared the growth of stocked and wild L. calcarifer in a tropical Australian river (Johnstone River) and stocked fish in a nearby impoundment (Lake Tinaroo). Growth of L. calcarifer in the Johnstone River appeared resource-limited, with juvenile fish in its lower freshwater reaches feeding mainly on small aytid shrimp and limited quantities of fish. Growth was probably greatest in estuarine and coastal areas than in the lower freshwater river. Fish in Lake Tinaroo, where prey availability was greater, grew faster than either wild or stocked fish in the lower freshwater areas of the Johnstone River. Growth of L. calcarifer was highly seasonal with marked declines in the cooler months. This was reflected in both stomach fullness and the percentage of fish with empty stomachs but the condition of L. calcarifer was similar across most sites. In areas where food resources appear stretched, adverse effects on resident L. calcarifer populations and their attendant prey species should be minimised through cessation of, or more conservative, stocking practices.

Growth Models with Corrections for the Retardative Effects of Tagging

1994 ◽  
Vol 51 (2) ◽  
pp. 263-267 ◽  
Author(s):  
Yongshun Xiao
Keyword(s):  
Growth Parameters ◽  
Growth Models ◽  
Simulated Data ◽  
Fish Growth ◽  
Lates Calcarifer ◽  
General Utility ◽  
Potential Applications ◽  
Length Increment ◽  
Animal Growth ◽  
Special Case

Length increment data from mark–recapture experiments are commonly used to obtain information on animal growth, assuming that tagging does not affect the growth of marked animals. The assumption is violated in many studies, but the effects of tagging on growth and estimates of growth parameters have not been and cannot be examined without appropriate models. This paper describes a model allowing quantification and estimation of the retarding effects of tagging on animal growth simultaneously with growth parameters in all existing growth models, reduction or elimination of biases in growth parameters induced by tagging, and relaxation of a key assumption in growth analysis using length increment data. A special case of this model was applied to simulated data and to tagging data from a centropomid perch (Lates calcarifer) to demonstrate its general utility. Tagging was inferred to have stopped the fish growth for 36.44 d (ASE = 12.70 d) if von Bertalanffy growth is assumed, but the period of recovery from tagging seemed size or age independent within the size range studied. If tagging retards animal growth, L∞ is slightly overestimated and K underestimated for unbiased data. Potential applications and limitations of the model are also discussed.

scholarly journals Making inference from wildlife collision data: inferring predator absence from prey strikes

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e3014 ◽  
Author(s):  
Peter Caley ◽  
Geoffrey R. Hosack ◽  
Simon C. Barry
Keyword(s):  
Prey Species ◽  
Red Fox ◽  
Prey Availability ◽  
Numerical Response ◽  
Practical Application ◽  
Ecological Inference ◽  
Predator Species ◽  
New Approach ◽  
Predictive Probability ◽  
Irreducible Uncertainty

Wildlife collision data are ubiquitous, though challenging for making ecological inference due to typically irreducible uncertainty relating to the sampling process. We illustrate a new approach that is useful for generating inference from predator data arising from wildlife collisions. By simply conditioning on a second prey species sampled via the same collision process, and by using a biologically realistic numerical response functions, we can produce a coherent numerical response relationship between predator and prey. This relationship can then be used to make inference on the population size of the predator species, including the probability of extinction. The statistical conditioning enables us to account for unmeasured variation in factors influencing the runway strike incidence for individual airports and to enable valid comparisons. A practical application of the approach for testing hypotheses about the distribution and abundance of a predator species is illustrated using the hypothesized red fox incursion into Tasmania, Australia. We estimate that conditional on the numerical response between fox and lagomorph runway strikes on mainland Australia, the predictive probability of observing no runway strikes of foxes in Tasmania after observing 15 lagomorph strikes is 0.001. We conclude there is enough evidence to safely reject the null hypothesis that there is a widespread red fox population in Tasmania at a population density consistent with prey availability. The method is novel and has potential wider application.

scholarly journals Gut content analysis of cattle egrets (Bubulcus ibis) in Asam Kumbang Crocodile Park, North Sumatra

2021 ◽  
Vol 912 (1) ◽  
pp. 012105
Author(s):  
E Jumilawaty ◽  
N Namira ◽  
A Anggelicha ◽  
A Hartanto
Keyword(s):  
Content Analysis ◽  
Prey Species ◽  
Prey Availability ◽  
Biological Control Agent ◽  
Food Resource ◽  
Control Agent ◽  
Gut Content Analysis ◽  
Gut Content ◽  
Dominant Group ◽  
Bubulcus Ibis

Abstract Cattle egret (Bubulcus ibis) is a widespread avian species inhabiting a variety of natural and artificial sites. Asam Kumbang Crocodile Park is one of establishments that occupied some portions of B. ibis habitat with no recent information on the food resource and prey availability for the viability of B. ibis. To this aim, we collected 10 random individuals of B. ibis to be sacrificed for gut content analysis of prey species. A total of 19 taxa was found as prey items in the gut of B. ibis with the dominant group from insects (Orthoptera, Scolopendromorpha). The diversity of prey species was categorized as moderate with intraspecific diet variation which formed four guilds that fed on specific taxa namely Group 1 (Haplotaxida, Lepidoptera, Anurans), Group 2 (Blattodea, Coleoptera, Araneae), Group 3 (Orthoptera, Scolopendromorpha); and Group 4 (Dermaptera, Squamata). Oxya chinensis and Oxya velox are important rice grasshopper pests that were also found in the gut of B. ibis reflecting their potential function as biological control agent.

Ecology of gyrfalcons, Falco rusticolus, in the central Canadian Arctic: diet and feeding behaviour

1988 ◽  
Vol 66 (2) ◽  
pp. 334-344 ◽  
Author(s):  
K. G. Poole ◽  
D. A. Boag
Keyword(s):  
Feeding Behaviour ◽  
Prey Species ◽  
Prey Availability ◽  
Optimal Foraging Theory ◽  
Ground Squirrels ◽  
Spermophilus Parryii ◽  
Falco Rusticolus ◽  
Lagopus Mutus ◽  
Spring Arrival ◽  
Average Size

Diet and aspects of feeding behaviour in a population of gyrfalcons (Falco rusticolus) in the Northwest Territories were examined between 1984 and 1986. Three prey species, rock ptarmigan (Lagopus mutus), arctic ground squirrel (Spermophilus parryii), and arctic hare (Lepus arcticus), composed 96.5% of total prey biomass identified. Ptarmigan and hares were taken in May and June of all years (98.2% of biomass). Juvenile squirrels were used extensively in July and August of 1984 and 1985 but not in 1986, when squirrel production fell to almost zero; ptarmigan continued to be the dominant prey species throughout that summer. Because densities of breeding ptarmigan remained relatively constant during the study, but those of juvenile ground squirrels did not, it appeared that gyrfalcons responded functionally to varying availability of prey. Mean weight (250 g) of prey taken by male gyrfalcons was significantly less than the weight (330 g) of prey taken by females. As predicted by optimal foraging theory, average size of prey brought to the nest increased as time away from the nest increased. Conditions of food abundance were observed at most nests, suggesting that the amount of food available during the nestling period was not limiting production. We suggest that annual production is a function of spacing of pairs, which is set during courtship and prelaying, when prey availability is at its yearly low and when males must forage for both members of the pair. The fact that most gyrfalcon pairs initiated laying only after the spring arrival of migrating ptarmigan is consistent with this conclusion.

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.

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.

Comparison between the feeding habits of spotted eagle ray (Aetobatus narinari) and their potential prey in the southern Gulf of Mexico

2018 ◽  
Vol 99 (3) ◽  
pp. 661-672 ◽  
Author(s):  
F. Serrano-Flores ◽  
J.C. Pérez-Jiménez ◽  
I. Méndez-Loeza ◽  
K. Bassos-Hull ◽  
M.J. Ajemian
Keyword(s):  
Gulf Of Mexico ◽  
Prey Species ◽  
Prey Availability ◽  
Feeding Habits ◽  
Small Scale ◽  
Potential Prey ◽  
Important Prey ◽  
Ecological Aspects ◽  
Southern Gulf Of Mexico ◽  
Spotted Eagle Ray

In the southern Gulf of Mexico, the spotted eagle ray (Aetobatus narinari) is the second most frequently caught batoid in small-scale fisheries off Campeche. Ecological aspects of this ray are unknown in this region, hampering the understanding of the relationship between its distribution and prey availability in the fishing area. In order to study the feeding habits of this batoid and characterize its potential prey in the study area, stomachs and intestines of 154 specimens (68 females and 86 males) were analysed. The results indicated that A. narinari near Campeche is a specialist and selective predator that feeds mainly on gastropods (92.7% IRI), with no significant differences in the diet found between sexes, size groups, or between stomach and intestine contents. In addition, the results indicated that the most important prey species in the diet were among the most common benthic species in three of the four sampling transects positioned in or adjacent to fishing areas for rays. These most important prey species were Strombus pugilis (53.33% IRI) and Americoliva reticularis (25.6% IRI). Other prey species included Lobatus costatus (5.6% IRI) and Petrochirus diogenes (3.6% IRI). This study suggests that this widely distributed ray species feeds in Campeche's coastal waters and that the study of its potential prey increases the understanding of ecological aspects of the species, which emphasizes the added importance of monitoring fishery impacts on prey species (e.g. the conch fishery off Campeche) to help support integrated assessment and management of fisheries.

scholarly journals Estimating population densities and biomass of ungulates in the temperate ecosystem of Bhutan

Oryx ◽  
2010 ◽  
Vol 44 (3) ◽  
pp. 376-382 ◽  
Author(s):  
Sonam Wangyel Wang
Keyword(s):  
Prey Species ◽  
Prey Availability ◽  
Crop Damage ◽  
Panthera Tigris ◽  
Population Densities ◽  
Cuon Alpinus ◽  
Livestock Density ◽  
Large Predators ◽  
Cervus Unicolor ◽  
Wild Pig

AbstractIn this study I estimate population densities and biomass of the major prey species of tiger Panthera tigris, leopard Panthera pardus and dhole Cuon alpinus in Bhutan’s temperate ecosystem and recommend measures for reducing crop damage whilst simultaneously protecting ungulate populations. Thirty-two transects totalling 849 km were walked to estimate densities and biomass of ungulates and primates in Bhutan’s Jigme Singye Wangchuck National Park during 2005–2006. Adequate detections (> 40 sightings) for analysis using Distance were obtained for wild pig Sus scrofa (n = 54), muntjac Munticus muntjac (n = 102) and sambar Cervus unicolor (n = 48). Because of similarity in morphology and habitat use, density of serow Capricornis sumatraensis was estimated using the detection probability for sambar. Detections for langur Trachypithecus geei and macaque Macca mulatta were combined (n = 39) to estimate primate density. Mean estimated densities were 3.68 wild pig, 2.17 muntjac, 1.19 sambar, 2.37 primates and 0.36 serow km-2. The three primary prey species of large predators, wild pig, sambar and muntjac, provided a biomass of 379 kg km-2, which could support up to 1.2 tigers per 100 km2. However, the presence of other sympatric carnivores competing for prey in the same area suggests that the actual number of tigers that could be supported is lower. Livestock (density, 6.0 km-2; biomass, 615 kg km-2) apparently supplement prey availability. Ungulate density in the study area is generally low compared to other areas in the Indian sub-continent, and this may be due to conflicts with farmers, excessive grazing of livestock in the forest and the rugged terrain.

scholarly journals Prey choice and habitat use of people exploiting intertidal resources

2002 ◽  
Vol 29 (2) ◽  
pp. 238-252 ◽  
Author(s):  
W.F. de Boer ◽  
A.-F. Blijdenstein ◽  
F. Longamane
Keyword(s):  
Prey Species ◽  
Prey Availability ◽  
Spring Tide ◽  
Dry Weight ◽  
Intake Rate ◽  
Mangrove Forests ◽  
Prey Choice ◽  
Relative Value ◽  
The Mean ◽  
The Impact

The impact of human exploitation depends mostly on the size of the catch and the species targeted. The value of a species is an important explanatory variable in understanding human impact. Co-management of resources should take into account these different resource values, when evaluating exploitation strategies. The prey choice and foraging behaviour of women and children searching for crabs and shells on the intertidal area at Inhaca Island, South Mozambique, were investigated using optimal foraging theory. This theoretical framework offers the possibility to understand the reasoning of an exploitation strategy and the preference for certain prey species. The number of people was registered, catches were analysed, and timing and substrate choice were recorded. The value of species was estimated using contingency tables. Women were more efficient than children, as their catch was heavier, and the mean weight/animal was larger. The density of women and their timing were positively correlated to prey availability. During neap tide, they spread their visit over more of the low water period and collected crabs by digging in the mangrove forests. No digging occurred during spring tide when a larger area was exposed, the total abundance of species increased, and more species became available. Women then switched to a second strategy, targeting swimming crabs in the tidal channel. Mean neap and spring tide catches were equal (133 g ash-free dry weight per person), but spring catches comprised significantly fewer animals per catch (42 against 123 per person), and mean animal weight was larger (5.4 against 3.0 g ash-free dry-weight per person). Diet breadth was narrower during spring tide, and decreased significantly with increased catch weight. Species with profitabilities (energy intake/handling time) lower than the mean intake rate of 0.024–0.028 g ash-free dry weight s−1 were generally excluded from the diet. The prey preference was positively related to the relative value ranks of the prey species, as measured by ranking of species by women. Women maximized the cumulative relative value ranks during spring tide, instead of total weight. Using this analysis, differences in prey choice and spatial differences in exploitation can be understood as a strategy aimed at maximizing intake and the relative value of a prey species.

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