scholarly journals Weekly changes in prey availability for and the selective feeding of sea trout (Salmo trutta L.) larvae stocked in small forest streams

2017 ◽  
Vol 25 (3) ◽  
pp. 135-143
Author(s):  
Józef Domagała ◽  
Robert Czerniawski ◽  
Tomasz Krepski
Keyword(s):  
Salmo Trutta ◽  
Size Range ◽  
Prey Size ◽  
Prey Availability ◽  
Stomach Contents ◽  
Benthic Organisms ◽  
Sea Trout ◽  
In The Wild ◽  
Forest Streams ◽  
Small Forest

Abstract This study examined the availability of food and its selection by sea trout Salmo trutta L. fry in the first four weeks of life after yolk sac resorption. The food base and stomach contents of sea trout fry after release in the wild were determined. The study was performed in two small forest streams from April 25 to May 23, 2014. Macro-zoobenthos that comprised the food base for the fry were collected from the streams weekly using a bottom scraper. On the same day, the fry were captured with electrofishing gear. Analysis of the width of the benthic organisms in the food base and in the fish stomachs indicated the prey size range that the fish were feeding on. Further, the study showed that all food items found in both streams during the study weeks were also represented in the intensity of the fish: Cyclopoida, the larvae of Baetidae, Simuliidae and Nemouridae.

Prey availability and selective feeding of sea trout (Salmo trutta L., 1758) fry stocked in small forest streams

2014 ◽  
Vol 31 (2) ◽  
pp. 375-380 ◽  
Author(s):  
J. Domagała ◽  
T. Krepski ◽  
R. Czerniawski ◽  
M. Pilecka-Rapacz
Keyword(s):  
Salmo Trutta ◽  
Prey Availability ◽  
Selective Feeding ◽  
Sea Trout ◽  
Forest Streams ◽  
Small Forest

Trophic ecology of a benthic intertidal hydroid, Tubularia crocea, at Mar del Plata, Argentina

2005 ◽  
Vol 85 (2) ◽  
pp. 307-312 ◽  
Author(s):  
Gabriel N. Genzano
Keyword(s):  
Trophic Ecology ◽  
Feeding Rate ◽  
Prey Availability ◽  
Stomach Contents ◽  
Dry Weight ◽  
Benthic Organisms ◽  
Food Items ◽  
The Mean ◽  
The Relationship ◽  
Prey Items

The trophic ecology and seasonal changes in the diet of the intertidal hydrozoan Tubularia crocea were studied analysing the enteron contents of hydranths collected each season of the year. The relationship between feeding rate, prey availability, and re-suspension processes caused by tidal currents was also assessed. The most prevalent food items were diatoms and crustaceans. The most remarkable differences occurred during summer, when crustaceans were more abundant than diatoms. Conversely, diatoms were the most abundant prey during other seasons, and they were almost the only prey found during winter. There was no relationship between abundances of primary prey items in the water column and their occurrences in stomach contents. Instead, most prey items consisted of benthic organisms, primarily two species of diatoms (Grammatophora marina and Licmophora abreviatta) and fragments (usually appendages) of the amphipods Caprella sp. and Jassa falcata. Most food items were digested within 4–4·5 hours. The mean number of items captured per polyp per day was determined to be 115·2±19·2 in summer, 93·6±14·4 in autumn, 76·8±21·6 in winter and 199·2±31·2 in spring. Prey biomass (dry weight) polyp−1 d−1 was 5·1 μg in summer, 2·3 μg in autumn, 1·8 μg in winter, and 6·3 μg in spring. These values, in relation to hydranth biomass (55·3 μg; dry weight), were equivalent to a food intake polyp−1 d−1 of 9·3%, 4·2%, 3·2% and 11·5% of its own weight, respectively.

The Diets of Two Coexisting Species of Antechinus (Marsupialia: Dasyuridae).

1980 ◽  
Vol 7 (3) ◽  
pp. 365 ◽  
Author(s):  
S Hall
Keyword(s):  
Size Range ◽  
Prey Size ◽  
Diversity Index ◽  
Large Population ◽  
Stomach Contents ◽  
Trophic Diversity ◽  
Individual Variations ◽  
Faecal Samples ◽  
Antechinus Stuartii ◽  
Coexisting Species

An analysis of faecal samples and stomach contents of Antechinus stuartii and A. swainsonii inhabiting forest in southern Victoria revealed a large overlap in the type and size of prey items taken by these dasyurids. The frequencies of 23 prey types and 15 prey sizes in the diets of these predators were both positively correlated. Weevils (Coleoptera, Curculionidae) represented the only difference in prey types not attributed to individual variations. A. stuartii took more, and a wider size range of, weevils than did A. swainsonii; the trophic diversity index of prey types was greater for A. stuartii. The larger A. swainsonii took more prey greater than 20 mm; it took prey on the average 23% longer and 75% heavier than did A. stuartii; the trophic diversity index of prey size was greater for A. swainsonii. It is concluded that these morphologically distinct predators are exploiting the same large population of prey. They are both generalists and appear to be opportunistic feeders.

scholarly journals Habitat-specific production of aquatic and terrestrial invertebrate drift in small forest streams: implications for drift-feeding fish

2017 ◽  
Vol 74 (8) ◽  
pp. 1208-1217 ◽  
Author(s):  
Sean M. Naman ◽  
Jordan S. Rosenfeld ◽  
Laura C. Third ◽  
John S. Richardson
Keyword(s):  
Prey Availability ◽  
Channel Structure ◽  
Invertebrate Drift ◽  
Entry Rate ◽  
Terrestrial Invertebrates ◽  
Drift Feeding ◽  
Drift Flux ◽  
Forest Streams ◽  
Channel Unit ◽  
Small Forest

The influence of stream channel structure on the production of prey for drift-feeding fish is not well understood. We quantified drift production, the entry rate per streambed area, and drift flux, the total export rate per channel unit, in three second-order, forested streams in southwest British Columbia, Canada. We tested whether (1) drift production was higher in riffles than in pools, (2) drift flux increased with riffle length, and (3) prey body size was larger from riffles relative to pools and from terrestrial drop relative to aquatic drift. Total and aquatic-derived drift production (mg·m−2·h−1) was ∼3.5 times higher in riffles relative to pools; however, terrestrial drift did not differ between channel types. Total drift flux (mg·h−1) was positively related to riffle length. Terrestrial invertebrates were approximately three times larger than aquatics, and invertebrates from riffles were approximately three times larger on average than those from pools. These results suggest that channel structure directly affects prey availability and prey quality for drift-feeding fish and that long riffles may be key areas of prey generation.

scholarly journals Survival rate and growth in the wild of sea trout (Salmo trutta L.) fry obtained using frozen semen

2014 ◽  
Vol 22 (4) ◽  
pp. 265-270 ◽  
Author(s):  
Józef Domagała ◽  
Katarzyna Dziewulska ◽  
Robert Czerniawski
Keyword(s):  
Survival Rate ◽  
Salmo Trutta ◽  
Condition Factor ◽  
Growth And Survival ◽  
Sea Trout ◽  
Natural Stream ◽  
Frozen Semen ◽  
Experimental Variant ◽  
In The Wild ◽  
Fresh Semen

Abstract The aim of the study was to assess the growth and development of sea trout, Salmo trutta L., fry obtained from frozen, thawed semen after the fish had been released into the wild and were feeding there. The semen was cryopreserved with either methanol (MeOH) or dimethyl sulfoxide (DMSO). Fresh eggs were collected and fertilized with the thawed semen. The control was eggs fertilized with fresh semen that had been kept on ice. The eggs were incubated and reared in a closed recirculating system. The fertilized eggs were counted for visible eye pigment. After rearing, three groups of fish were tagged and stocked into a stream. The fish aged 6 months were caught from the stream. The fish were measured, weighed, identified to which experimental variant they belonged, and their survival rate was estimated. No significant differences in survival rate, length, weight, or condition factor among the control, DMSO, and MeOH groups were noted during larval development in a closed recirculating system. These parameters were also similar in the control and experimental groups after the fish had grow in a natural stream. The use of frozen semen to fertilize fresh sea trout eggs resulted in a normal incubation process, larval stage, and regular fry growth and survival, both under laboratory conditions, and, most importantly, in the wild. The results indicate it is possible to use frozen semen for fry production and the restoration of wild fish populations.

Impact of live food on survival and growth of hatchery-reared sea trout (Salmo trutta trutta L.) parr in the wild

2014 ◽  
Vol 31 (1) ◽  
pp. 95-99 ◽  
Author(s):  
R. Czerniawski ◽  
J. Domagala ◽  
T. Krepski ◽  
M. Pilecka-Rapacz
Keyword(s):  
Salmo Trutta ◽  
Live Food ◽  
Sea Trout ◽  
In The Wild ◽  
Survival And Growth

Contrasting predation risks presented by introduced brown trout and native common river galaxias in New Zealand streams

1995 ◽  
Vol 52 (9) ◽  
pp. 1821-1833 ◽  
Author(s):  
Angus R. McIntosh ◽  
Colin R. Townsend
Keyword(s):  
New Zealand ◽  
Predation Risk ◽  
Brown Trout ◽  
Salmo Trutta ◽  
Visual Cues ◽  
Prey Availability ◽  
Stomach Contents ◽  
River System ◽  
Brown Trout Salmo Trutta ◽  
Nocturnal Increase

Alterations in the predation risk affecting macroinvertebrates in streams of the Taieri River system of New Zealand were assessed following the replacement of native common river galaxias (Galaxias vulgaris) in many sites by introduced brown trout (Salmo trutta). In laboratory channels, galaxias foraged on mayfly nymphs from benthic positions; they searched for prey at night but stayed in cover during the day except when attacking prey. Trout foraged from positions in the water column during day and night. There were no diel differences in foraging by galaxias but trout had higher reaction distances and consumed more during the day. No diel pattern was found in trout stomach contents in the field, probably because of a nocturnal increase in prey availability. Trout and galaxias populations in the field consumed similar biomasses of aquatic prey. However, these experiments indicate there have been subtle changes in the predation regime. Trout relied on visual cues to capture prey so predation risk was higher during the day and larger prey items were more at risk. In comparison, galaxias relied more on mechanical cues to capture prey and predation risk was similar during day and night.

Present Status of the Salmonids Atlantic Salmon and Sea-Trout in the Dutch Part of the River Rhine

1994 ◽  
Vol 29 (3) ◽  
pp. 37-41 ◽  
Author(s):  
W. G. Cazemier
Keyword(s):  
Atlantic Salmon ◽  
Salmo Trutta ◽  
Natural Populations ◽  
River Rhine ◽  
Sea Trout ◽  
The Past ◽  
The North ◽  
Trout Population ◽  
The North Sea ◽  
Heavy Pollution

In the past, the anadromous salmonids, Atlantic salmon (Salmo salar) and sea-trout (Salmo trutta), have formed natural populations in the river Rhine. From the beginning of the nineteenth century onwards, the greater part of the drainage area of the river has been gradually altered from a more or less rural and agricultural area, into a highly industrialised one with subsequent industrialisation, river-engineering and heavy pollution. These developments are considered to be the major cause for the disappearance of the populations of anadromous salmonid fish in the 1950s. The water quality has recovered significantly during the past 25 years. From about 1975 onwards, this process gave rise to a recovery of the anadromous trout population. Results of recent studies of the sea-trout migration pattern are presented. They reveal that nowadays these salmonids can complete their up- and downstream migrations from the North Sea to places, situated at hundreds of kilometres upward the river and vica versa. The numbers of recorded Atlantic salmon and catch locations in inland waters are presented. They show a significant increase since 1989. These phenomena can be understood as promising signs of the recovery of the Rhine aquatic ecosystem.

scholarly journals Prey Size Decline as a Unifying Ecological Selecting Agent in Pleistocene Human Evolution

Quaternary ◽  
2021 ◽  
Vol 4 (1) ◽  
pp. 7
Author(s):  
Miki Ben-Dor ◽  
Ran Barkai
Keyword(s):  
Prey Size ◽  
Prey Availability ◽  
Stone Tool ◽  
Foraging Efficiency ◽  
Energetic Cost ◽  
Large Prey ◽  
Biomass Density ◽  
Cultural Changes ◽  
Progressive Decline ◽  
Brain Expansion

We hypothesize that megafauna extinctions throughout the Pleistocene, that led to a progressive decline in large prey availability, were a primary selecting agent in key evolutionary and cultural changes in human prehistory. The Pleistocene human past is characterized by a series of transformations that include the evolution of new physiological traits and the adoption, assimilation, and replacement of cultural and behavioral patterns. Some changes, such as brain expansion, use of fire, developments in stone-tool technologies, or the scale of resource intensification, were uncharacteristically progressive. We previously hypothesized that humans specialized in acquiring large prey because of their higher foraging efficiency, high biomass density, higher fat content, and the use of less complex tools for their acquisition. Here, we argue that the need to mitigate the additional energetic cost of acquiring progressively smaller prey may have been an ecological selecting agent in fundamental adaptive modes demonstrated in the Paleolithic archaeological record. We describe several potential associations between prey size decline and specific evolutionary and cultural changes that might have been driven by the need to adapt to increased energetic demands while hunting and processing smaller and smaller game.

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