Social cues may advertise habitat quality to refuge-seeking conspecifics

Individuals travelling through landscapes may use the presence of conspecifics to evaluate habitat quality. Juvenile Atlantic salmon (Salmo salar L., 1758) are usually territorial and exhibit some degree of density-dependent regulation in wild populations. They are also vulnerable to heat stress and may need to locate a thermal refuge to offset metabolic costs above certain temperature thresholds. During July 2010, a heat wave resulted in water temperatures in the Miramichi River system exceeding 30 °C. During this period, salmon parr were observed aggregating in cold-water refugia at densities several orders of magnitude greater than usual. We tested whether groups of wild-caught salmon parr held at high densities (160 parr/m2) would have an attractant effect on free-swimming parr at three sites differing in temperature between 16.5 and 24 °C. Although neither temperature nor site influenced the number of parr that we observed, there were significantly more parr in close proximity (<1 m) to the artificial aggregations than to the controls. These results suggest that social cues from high-density aggregations of conspecifics during extreme temperature events may advertise the location of thermal refugia to others. Understanding how heat-stressed salmon locate refugia may prove valuable to ongoing conservation efforts given the likelihood of increasingly frequent and extreme high-temperature events

Size-mediated response to public cues of predation risk in a tropical stream fish

In order to investigate any size-dependent differences between behavioural patterns, wild-caught Hart's rivulus Rivulus hartii of varying sizes were exposed to chemical alarm cues extracted from the skin of conspecifics or heterospecific Poecilia reticulata, or a tank water control, in a series of laboratory trials. In response to conspecific alarm cues, R. hartii subjects of the range of body sizes tested exhibited consistent, size-independent antipredator behaviours that were characterized by decreased locomotory activity and foraging levels and increased refuging behaviour. Conversely, focal R. hartii demonstrated significant size-dependent trends in response to heterospecific alarm cues, with smaller individuals exhibiting antipredator responses and larger individuals shifting their behaviour to increased levels of activity consistent with a foraging, or predatory, response. These results show that the behavioural responses of individual R. hartii to publicly available chemical alarm cues from heterospecifics are mediated by the size of the receiver

Evaluating a light-louver system for behavioural guidance of age-0 white sturgeon

Water diversions for hydropower and other applications are some of the most disruptive alterations affecting fish populations in lotic systems. Although many different strategies have been developed to reduce lethal encounters with such infrastructure, few studies have evaluated different forms of behavioural guidance concurrently. Here, we combine an LED-based light guidance device (LGD) equipped with adjustable wavelength and strobing output with a reverse-configured louver rack to assess the effectiveness of this two-part behavioural guidance system on downstream movement through a bypass by age-0 white sturgeon (Acipenser transmontanus). Several combinations of LGD and louver settings were tested under both simulated day and night (low light) conditions in a laboratory setting. In the absence of the LGD, louver slat spacings of 10 or 20 cm were most effective at achieving downstream bypasses with greater success rates (~ two-fold greater) under night conditions tha

Cross-population responses to conspecific chemical alarm cues in wild Trinidadian guppies, Poecilia reticulata: Evidence for local conservation of cue production

Within freshwater fishes, closely related species produce alarm cues that are chemically similar, leading to conserved antipredator responses. Similar conservation trends are predicted for species with geographically isolated populations. Here, we tested this hypothesis with the guppy (Poecilia reticulata Peters, 1859) from two populations within the Aripo River, Trinidad. Free-ranging guppies in the Lower Aripo (high-predation population) exhibited more risk-aversive inspection behaviour towards a fish predator model paired with the alarm cues of guppies collected from the same population versus a river water control. In comparison, when paired with the alarm cues of guppies from the Upper Aripo (low-predation population), the response was intermediate. In the laboratory, we tested Upper and Lower Aripo guppies to the alarm cues of the same or different Aripo River donors, Quaré River guppies (a high-predation population from a different drainage), or a water control. Both Upper and Lower Aripo River guppies exhibited the highest intensity response to donors from the same population and the lowest intensity response to Quaré River donors, with the response to different Aripo donors being intermediate. Collectively, these results demonstrate a trend of intraspecific conservation of chemical alarm cue production, leading to population-specific responses to conspecific cues

Ontogenetic changes in chemical alarm cue recognition and fast-start performance in guppies (Poecilia reticulata)

Risk recognition and fast-start performance are critical to fish survival when faced with predators. Many fish species have been shown to recognize risks associated with chemical cues released by injured conspecifics. However, little is known about the ontogeny of “risk” recognition via damage-released chemical alarm cues and fast-start performance in prey fishes. The objectives of this study were to determine whether risk recognition and fast-start performance in guppies (Poecilia reticulata) exhibit ontogenetic variation, and whether there is a trade-off between risk recognition and fast-start performance. To achieve these objectives, individual guppies from replicate groups were assayed on one of the 1st, 7th, 14th, 21st, or 28th day after their birth. We found that both the risk recognition and fast-start performance in guppies

Preferences of age-0 white sturgeon for different colours and strobe rates of LED lights may inform behavioural guidance strategies

Many populations of migratory fish species, including white sturgeon (Acipenser transmontanus Richardson), are threatened due to modification of riverine systems and may experience downstream displacement or mortality at water intake structures. Efforts to reduce the impacts of these structures are beginning to incorporate behavioural guidance, where the sensory capabilities of fishes are exploited to repel them from high-risk areas or attract them towards desirable pat

Ontogeny of light avoidance in juvenile lake sturgeon

Hatchery-reared age 1+ and 4+ lake sturgeon (Acipenser fulvescens) were assayed to determine the effectiveness of coloured, strobing LED light guidance device (LGD) at achieving behavioural guidance for attraction or avoidance responses. Base

Comparison of the behavioral consequences and recovery patterns of largemouth bass exposed to MS-222 or electrosedation

Fish are commonly sedated to render them immobile and thus easier to handle for research, veterinary, and aquaculture practices. Since sedation itself imposes a significant challenge on the targeted fish, the selection of sedation methods that minimize physiological and behavioral disturbance and recovery time is essential. Two popular sedation methods include the chemical tricaine methanesulfonate (MS-222) and electrosedation. Although many studies have already investigated the physiological consequences of these methods, there is limited research examining the latent behavioral effects on fish. Using Largemouth Bass Micropterus salmoides as a model species, we compared the postsedation behaviors of fish that were sedated with either MS-222 or electrosedation to those of a control group exposed to the same handling protocol. Immediately after sedation, fish exposed to either treatment demonstrated lower reflex scores than the control group. Time to resume regular ventilation did not differ between chemically sedated and electrosedated fish; however, electrosedated fish regained equilibrium faster (mean ± SE = 154 ± 20 s) than fish that were exposed to MS-222 (264 ± 30 s). Locomotor activity and swimming performance were assessed at 5-, 30-, or 60-min intervals, beginning after individuals had recovered from sedation sufficiently to regain equilibrium. For all postsedation intervals, locomotor activity was two times greater in the electrosedated group than in the control and MS-222 groups. Other behavioral measures (refuge emergence time, activity level, and flight initiation distance) and swimming performance did not differ at 5, 30, or 60 min postrecovery for any of the treatment groups. Our results indicate that while both chemical and electrical sedation methods result in impairment (i.e., sedation) immediately after treatment, these behavioral effects do not persist beyond 5 min postrecovery, and the two methods have similar impacts on Largemouth Bass. However, we caution that these results cannot be extrapolated to other fish species without further study

Influence of hook type and live bait on the hooking performance of inline spinners in the context of catch-and-release brook trout Salvelinus fontinalis fishing in lakes

The objective of catch-and-release angling is for the fish to survive with minimal fitness consequences. However, fish survival can be compromised by a number of factors, especially anatomical hooking location. To evaluate whether hook type or bait influence hooking outcomes, we tested different combinations of hook (treble or single siwash hooks) and bait (hook tipped with worm or no worm) while angling for brook trout (Salvelinus fontinalis) with inline spinner-style fishing lures. The study was conducted at spring water temperatures (∼20 °C) in small lakes stocked with trout in southwestern Quebec, Canada. Incidences of hooking in the interior of the mouth (i.e. internal hooking) were uncommon (19%), did not differ significantly between hook types or bait treatments, and occurred independently of fish size. Reflex impairments after hook removal were not related to hook or bait treatment. Short-term mortality was quantified with 24 h holding in net pens and was determined to be infrequent for all treatment groups (treble/worm: 6%; treble/no worm: 5%; single/worm: 2%; single/no worm: 0%). Although no fish were hooked in the gills, esophagus, stomach, odds of mortality increased by 14.21 when fish were hooked internally, which is consistent with the position that hook placement is an important predictor of the fate of fish released by anglers. However, our finding that neither hook nor bait type significantly increased the odds of internal hooking, bleeding, reflex impairment, or mortality in this study suggests that restrictions imposed on the use of baited lures or certain hook types attached to lures when fishing may have little influence on short-term catch-and-release mortality of brook trout at these temperatures