Implications of territory size for the measurement and prediction of salmonid abundance in streams

Information about territory size is useful for both the measurement and prediction of salmonid abundance. Percent habitat saturation (PHS), the percentage of the stream area occupied by the territories of salmonid fishes, is a better measure of abundance than population density because the former integrates the effects of (a) several age-classes or species in a stream, and (b) variation in growth rate or sampling date. "Effective density" or "effective PHS," calculated by weighting crude density (no.·m-2) or PHS by the number of organisms in the sampling unit, more accurately reflects density from the organism's point of view than does crude density or PHS. Effective density and PHS of Atlantic salmon (Salmo salar) in Catamaran Brook, New Brunswick, increased by 0.4 fish per m2 and 4%, respectively, for each order of magnitude decrease in the area of the sampling unit. Literature data suggested that territory size is inversely related to food abundance and can be used to predict changes in salmonid abundance that accompany changes in food abundance. The allometry of territory size was a better predictor of the decline in density of a cohort of Atlantic salmon in Catamaran Brook than the allometry of metabolic requirements

Functional and trophic diversity of tropical headwater stream communities inferred from carbon, nitrogen and hydrogen stable isotope ratios

Tropical freshwaters support an immense diversity of fishes and invertebrates but are understudied in comparison to temperate systems. This is especially true of headwater streams, as only a small number of studies has assessed the trophic dynamics underpinning food web structure in these streams. We used stable isotopes of carbon, nitrogen and hydrogen to determine the resource use of dominant invertebrate guild and fishes in seven headwater streams in Eastern and Western Thailand, and assessed the functional and trophic diversity of each community using isotope food web metrics. Benthic invertebrates (95% credibility interval: 37–85%) and fishes (39–79%) obtained most of their resources from autochthonous sources in each stream but allochthonous and autochthonous specialists were evident in each community. We observed an increase in isotopic diversity of fishes associated with increasing stream size, but this was primarily driven by an increase in the range of isotope ratios of allochthonous and autochthonous food web endmembers rather than an increase in functional diversity. Maximum trophic position did increase with stream size. The snakehead, Channa gachua, was enriched in 2H relative to all other fishes, possibly reflecting facultative air breathing by this species. Fish communities in the headwater streams analysed filled a variety of trophic niches, predominantly fuelled by autochthonous primary production

The use of PIT technology in fish research : a review

The use of PIT technology in fish research : a review. Seminar on PIT Technolog

Field test of a new method for tracking small fishes in shallow rivers using passive integrated transponder (PTI) technology

International audienc

Estimating the contribution of sympatric anadromous and freshwater resident brown trout to juvenile production

 Carbon and nitrogen stable isotope analysis was used to study the reproductive contributions of anadromous and freshwater resident female brown trout (Salmo trutta L.) in La Roche Brook (Normandy, France), where both forms live in sympatry. Sixty-nine emerging fry were sampled by electrofishing in three different locations in the lower, middle and upper reaches of the stream, in March–April 2002. A collection of samples with known origin (brown trout eggs and fin tissues and benthic invertebrates) allowed classification of each emerging fry as the progeny of freshwater resident (δ13C = –26.0‰ ± 0.8 s.d.; δ15N = 12.5‰ ± 1.4 s.d.) or anadromous (δ13C = –18.8‰ ± 0.6 s.d., δ15N = 14.8‰ ± 0.9 s.d.) female brown trout. It was then possible to estimate the relative contribution (33%) of anadromous females to the population of fry that emerged from redds in 2002 and to evaluate the extent to which freshwater and anadromous spawning grounds overlapped in the stream

Efficacy and accuracy of portable PIT-antennae when locating fish in ice-covered streams

 Active tracking of passive integrated transponder (PIT)-tags using portable antennae is becoming an increasingly common technique in fish habitat studies in shallow rivers. We carried out “blind testing” to test the efficacy (% tags found) and accuracy (distance between predicted and true tag location) of a portable antenna system (Texas Instruments) in winter conditions using 23-mm PIT-tags. Up to 90 cm reading range was achieved and signals penetrated ice, rock, wood and water. In the “blind test” trials, a majority of the hidden tags (N = 12–30) were found indicating high tracking efficacy. PIT-tags that were oriented with their cylindrical axis parallel to the plane of the antenna coil inductor loop resulted in a bimodal detection field that had low detection range in the centre of the loop. The utilization of this bimodal detection field proved to be a very accurate method for identifying tag position (mean ± SE distance from predicted to true tag location 10.9 ± 1.4 cm) and thus well suited for microhabitat and activity studies in winter conditions. Aggregations of tags (multiple tags within 1 m2) and obstacles for the antenna maneuvering (e.g., boulders, logjams) reduced the pinpointing accuracy (mean ± SE 13.3 ± 1.8 cm), but the reduction in accuracy was statistically non-significant between the single and aggregated tags

Distinguishing seasonal foraging and refuge-seeking movement patterns of individual Atlantic salmon parr in a river-tributary complex

Distinguishing seasonal foraging and refuge-seeking movement patterns of individual Atlantic salmon parr in a river-tributary complex. 135. American Fisheries Society Annual Meetin

Detecting marine nutrient and organic matter inputs into multiple trophic levels in streams of Atlantic Canada and France.

Detecting marine nutrient and organic matter inputs into multiple trophic levels in streams of Atlantic Canada and France.. Challenges for diadromous fishes in a dynamic global environmen