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Fish Swimming Performance: Insights from Theory and Experiments
Full text linkL'abstract è presente nell'allegato / the abstract is in the attachmen
Repeatability and reliability of the provoked escape response test for estimating fish maximum swimming speeds
No full textIn fish, burst swimming performance is essential for escaping predators, capturing prey, and overcoming velocity barriers. Forced swimming trials often underestimate performance, whereas volitional swimming tests provide more ecologically relevant data, but require costly infrastructure. A cost-effective alternative is the provoked escape response test, where an object is dropped near the fish to trigger an escape response, and maximum swimming speed is estimated over a pre-determined time-period. The robustness of this test has, however, been little investigated. Here we test its repeatability at both the individual and group levels by running two repeated trials on 118 individuals of the Padanian goby (Padogobius bonelli) on two consecutive days. The estimated maximum swimming speed was not repeatable at the individual fish level, suggesting that the test may be unreliable when individual fish performance measures are important. The testing protocol did consistently show that large fish outperform small fish and remains a useful, simple, and cheap method for estimating average swimming performance and for comparing the performance between groups. Lower performance in the second compared to the first test indicates that fish experience, such as habituation or stress, can influence estimated maximum swimming speeds, suggesting that absolute estimates should be used with caution
The interplay of group size and flow velocity modulates fish exploratory behaviour
Full text linkSocial facilitation is a well-known phenomenon where the presence of organisms belonging to the same species enhances an individual organism's performance in a specific task. As far as fishes are concerned, most studies on social facilitation have been conducted in standing-water conditions. However, for riverine species, fish are most commonly located in moving waters, and the effects of hydrodynamics on social facilitation remain largely unknown. To bridge this knowledge gap, we designed and performed flume experiments where the behaviour of wild juvenile Italian riffle dace (Telestes muticellus) in varying group sizes and at different mean flow velocities, was studied. An artificial intelligence (AI) deep learning algorithm was developed and employed to track fish positions in time and subsequently assess their exploration, swimming activity, and space use. Results indicate that energy-saving strategies dictated space use in flowing waters regardless of group size. Instead, exploration and swimming activity increased by increasing group size, but the magnitude of this enhancement (which quantifies social facilitation) was modulated by flow velocity. These results have implications for how future research efforts should be designed to understand the social dynamics of riverine fish populations, which can no longer ignore the contribution of hydrodynamics
Passage performance of three small-sized fish species in a Vertical Slot Fishway with and without overhead cover
No full textHydropower dams block fish movement, cause river fragmentation, and constitute a threat to biodiversity worldwide. Vertical Slot Fishways (VSF) are a widespread solution to mitigate these effects by enabling fish passage at obstacles. In the past, fish passage research has focused mainly on strong swimming salmonids, often resulting in knowledge gaps and low passage success for other fish species, especially small-sized ones. In addition, although hydrodynamics is fundamental to assess the functionality of a fishway, other environmental factors can impact passage success. Light can affect several behaviors in fish and often plays a role in fish migration and movement. At fishways, light can both promote and hinder passage, with highly species-specific effects remaining underexplored for many species. Here we study the passage performance in an alternatingly open and covered VSF of three small-sized fish species: brook barbel (Barbus caninus), European bullhead (Cottus gobio), and Italian riffle dace (Telestes muticellus). Passage success was very high for brook barbel (100 %) and Italian riffle dace (95.2 %) while fewer European bullhead (46.4 %) successfully passed the fishway. Fish showed a preference for passage without overhead cover: both brook barbel and Italian riffle dace displayed lower overall passage rates under covered compared to open conditions, and entry rates were lower with cover for all three species
Decoding burst swimming performance: a scaling perspective on time-to-fatigue
Full text linkFatigue curves quantify fish swimming performance, providing
information about the time (Tf) fish can swim against a steady flow
velocity (Uf
) before fatiguing. Such curves represent a key tool for many
applications in ecological engineering, especially for fish pass design
and management. Despite years of research, though, our current ability
to model fatigue curves still lacks theoretical foundations and relies
primarily on fitting empirical data, as obtained from time-consuming and
costly experiments. In the present article, we address this shortcoming
by proposing a theoretical analysis that builds upon concepts of fish
hydrodynamics to derive scaling laws linking statistical properties of Tf to
velocities Uf
, pertaining to the so-called burst range. Theoretical arguments,
in the present study, suggest that the proposed scaling laws may hold
true for all fish species and sizes. A new experimental database obtained
from over 800 trials and five small-sized Cypriniformes support theoretical
predictions satisfactorily and calls for further experiments on more fish
species and sizes to confirm their general validity
The effect of in-flume habituation time and fish behaviour on estimated swimming performance
Full text linkSwimming performance is important for fish migration, habitat selection, and predator-prey interaction, as well as for fish passage design. Procedural choices made when experimentally estimating it may influence the results. Systematic experiments were conducted to study the effect of different in-flume habituation times, habituation behaviour, and the use of external encouragement on burst swimming performance of Rutilus aula, a small-sized cyprinid, in a fixed velocity testing protocol. Increasing habituation times from 30 s to 5 or 20 min substantially increased the success proportion of swimming trials and estimated fish swimming performance, with no difference between the latter two habituation times. Fish resting on the downstream grid before the start of testing velocity outperformed those who swam during habituation and transition periods. Fish swimming volitionally in response to flow at testing velocity showed a significantly improved performance compared to fish motivated by external poking. The results of this study highlight that in-flume habituation time is important, and fish behaviour before actual testing may influence the outcomes of swimming performance results
Survival and swimming performance of a small-sized Cypriniformes (Telestes muticellus) tagged with passive integrated transponders
Full text linkItalian riffle dace (Telestes muticellus, Bonaparte 1837) is a small-bodied Leuciscidae native to the Italian Peninsula, of which little is known about the ecology and individual movements in nature. Passive Integrated Transponder (PIT) telemetry is used to track fish movements and behaviour. The basic assumption is that the PIT-tagged organism’s performances do not differ considerably from their natural behaviour. Here we present the first evaluation of potential tagging effects in the genus Telestes. The survival rate and tag retention were compared between two different tag implantation methods – injector gun and scalpel incision - and pit-tagging effects on swimming performance were evaluated. Five weeks after tagging, Italian riffle dace demonstrated high survival rates in all treatments: 94.8% for fish tagged with injector gun (n=58), 100% for scalpel incision method (n=58), and 98.3% for controls (n=58). The tag re-tention was 96.6% for gun treatment and 100% for scalpel treatment. Prolonged swimming performance, tested 22-23 days after tagging, showed a reduction in endurance (time-to-fatigue) for scalpel treatment (n=22) compared to the control group (n=21), while no difference in maximum swimming velocity was observed. We conclude that PIT tagging is a suitable technique for Italian riffle dace, showing high survival and PIT retention and no effect on maximum swimming speed. Significantly lower prolonged swimming performance, although likely less ecologically important, shows that tagging is not without costs. Potential biases need to be evaluated on a study-by-study basis, and future studies should explore behavioural tagging effects in natur
Survival and Swimming Performance of Small-Sized Gobiidae Implanted with Mini Passive Integrated Transponders (PIT-Tags)
Full text linkTelemetry techniques are important tools in freshwater fish ecology but are limited by the
size of the fish in relation to the size of the electronic tags. The emergence of very small PIT tags
(8 mm, mini PIT tags) opens the door to study the individual movement and behavior of small-sized
fish species and life stages previously outside the scope of fish telemetry. Although high survival
from mini PIT tags have been shown in some groups of fish, suitability assessments are lacking
for many taxa, and potential behavioral effects have rarely been evaluated. Here, we evaluate the
survival tagging effects in small-sized (35–76 mm) Padanian goby (Padogobius bonelli) implanted with
mini PIT tags. PIT-tagging was associated with high survival and tag retention in the tagged fish.
No effects of PIT-tagging on volitional swimming activity nor on maximum swimming speed were
found. Similar results were obtained implanting larger tags (12 mm) in gobies down to 50 mm in
length. Our results indicate that PIT telemetry—using mini PIT tags—is applicable for the study of
behavior and movement in small-sized gobie
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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