Visual and Chemical Prey Cues as Complementary Predator Attractants in a Tropical Stream Fish Assemblage

To date, little attention has been devoted to possible complementary effects of multiple forms of public information similar information on the foraging behaviour of predators. In order to examine how predators may incorporate multiple information sources, we conducted a series of predator attraction trials in the Lower Aripo River, Trinidad. Four combinations of visual (present or absent) and chemical cues (present or absent) from each of two prey species were presented. The occurrences of three locally abundant predatory species present within a 1 m radius of cue introduction sites were recorded. The relative attractiveness of cue type to each predator was directly related to their primary foraging modes, with visual ambush predators demonstrating an attraction to visual cues, benthivores to chemical cues, and active social foragers demonstrating complementary responses to paired cues. Predator species-pair counts were greatest in response to cues from the more abundant prey species, indicating that individuals may adopt riskier foraging strategies when presented with more familiar prey cues. These differences in predator attraction patterns demonstrate complementary effects of multiple sensory cues on the short-term habitat use and foraging behaviour of predators under fully natural conditions

Nonconsumptive Effects of Predation and Impaired Chemosensory Risk Assessment on an Aquatic Prey Species

Weak levels of acidity impair chemosensory risk assessment by aquatic species which may result in increased predator mortalities in the absence of compensatory avoidance mechanisms. Using replicate populations of wild juvenile Atlantic salmon (Salmo salar) in neutral and acidic streams, we conducted a series of observational studies and experiments to identify differences in behaviours that may compensate for the loss of chemosensory information on predation risk. Comparing the behavioural strategies of fish between neutral and acidic streams may elucidate the influence of environmental degradation on nonconsumptive effects (NCEs) of predation. Salmon in acidic streams are more active during the day than their counterparts in neutral streams, and are more likely to avoid occupying territories offering fewer physical refugia from predators. Captive cross-population transplant experiments indicate that at equal densities, salmon in acidic streams do not demonstrate relative decreases in growth rate as a result of their different behavioural strategies. Instead, altering diel activity patterns to maximize visual information use and occupying relatively safer territories appear sufficient to offset increased predation risk in acidic streams. Additional strategies such as elevated foraging rates during active periods or adopting riskier foraging tactics are necessary to account for the observed similarities in growth rates

Fishing-induced versus natural selection in different brown trout (Salmo trutta) strains

Wild, adfluvial brown trout (Salmo trutta) are iconic targets in recreational fisheries but also endangered in many native locations. We compared how fishing and natural selection affect the fitness-proxies of brown trout from two pure angling-selected strains and experimental crosses between an adfluvial, hatchery-bred strain and three wild, resident strains. We exposed age 1+ parr to predation risk under controlled conditions where their behaviour was monitored with PIT-telemetry, and stocked age 2+ fish in two natural lakes for experimental fishing. Predation mortality (16% of the fish) was negatively size-dependent, while capture probability, also reflecting survival, in the lakes (38.9% of the fish) was positively length- and condition- dependent. Angling-induced selection against low boldness and slow growth rates relative to gillnet fishing indicated gear-dependent potential for fisheries-induced evolution in behaviours and life-histories. Offspring of wild, resident fish showed slower growth rates than the crossbred strains. Strain effects suggested significant heritable scope for artificial selection on life-history traits and demonstrated that choices of fish supplementation by stocking may override the genetic effects induced by angling.Peer reviewe

Global Night-Time Lights for Observing Human Activity

We present a concept for a small satellite mission to make systematic, global observations of night-time lights with spatial resolution suitable for discerning the extent, type and density of human settlements. The observations will also allow better understanding of fine scale fossil fuel CO2 emission distribution. The NASA Earth Science Decadal Survey recommends more focus on direct observations of human influence on the Earth system. The most dramatic and compelling observations of human presence on the Earth are the night light observations taken by the Defence Meteorological System Program (DMSP) Operational Linescan System (OLS). Beyond delineating the footprint of human presence, night light data, when assembled and evaluated with complementary data sets, can determine the fine scale spatial distribution of global fossil fuel CO2 emissions. Understanding fossil fuel carbon emissions is critical to understanding the entire carbon cycle, and especially the carbon exchange between terrestrial and oceanic systems

Provenance and threat-sensitive predator avoidance patterns in wild-caught Trinidadian guppies

The antipredator behaviour of prey organisms is shaped by a series of threat-sensitive trade-offs between the benefits associated with successful predator avoidance and a suite of other fitness-related behaviours such as foraging, mating and territorial defence. Recent research has shown that the overall intensity of antipredator response and the pattern of threat-sensitive trade-offs are influenced by current conditions, including variability in predation risk over a period of days to weeks. Here, we tested the hypothesis that long-term predation pressure will likewise have shaped the nature of the threat-sensitive antipredator behaviour of wild-caught Trinidadian guppies (Poecilia reticulata). Female guppies were collected two populations that have evolved under high- and low-predation pressure, respectively, in the Aripo River, Northern Mountain Range, Trinidad. Under laboratory conditions, we exposed shoals of three guppies to varying concentrations of conspecific damage-released chemical alarm cues. Lower Aripo (high-predation) guppies exhibited the strongest antipredator response when exposed to the highest alarm cue concentration and a graded decline in response intensity with decreasing concentrations of alarm cue. Upper Aripo (low-predation) guppies, however, exhibited a nongraded (hypersensitive) response pattern. Our results suggest that long-term predation pressure shapes not only the overall intensity of antipredator responses of Trinidadian guppies, but also their threat-sensitive behavioural response patterns

On the relevance of animal behavior to the management and conservation of fishes and fisheries

There are many syntheses on the role of animal behavior in understanding and mitigating conservation threats for wildlife. That body of work has inspired the development of a new discipline called conservation behavior. Yet, the majority of those synthetic papers focus on non-fish taxa such as birds and mammals. Many fish populations are subject to intensive exploitation and management and for decades researchers have used concepts and knowledge from animal behavior to support management and conservation actions. Dr. David L. G. Noakes is an influential ethologist who did much foundational work related to illustrating how behavior was relevant to the management and conservation of wild fish. We pay tribute to the late Dr. Noakes by summarizing the relevance of animal behavior to fisheries management and conservation. To do so, we first consider what behavior has revealed about how fish respond to key threats such as habitat alteration and loss, invasive species, climate change, pollution, and exploitation. We then consider how behavior has informed the application of common management interventions such as protected areas and spatial planning, stock enhancement, and restoration of habitat and connectivity. Our synthesis focuses on the totality of the field but includes reflections on the specific contributions of Dr. Noakes. Themes emerging from his approach include the value of fundamental research, management-scale experiments, and bridging behavior, physiology, and ecology. Animal behavior plays a key role in understanding and mitigating threats to wild fish populations and will become more important with the increasing pressures facing aquatic ecosystems. Fortunately, the toolbox for studying behavior is expanding, with technological and analytical advances revolutionizing our understanding of wild fish and generating new knowledge for fisheries managers and conservation practitioners.publishedVersio

Ten practical realities for institutional animal care and use committees when evaluating protocols dealing with fish in the field

Institutional Animal Care and Use Committee’s (IACUCs) serve an important role in ensuring that ethical practices are used by researchers working with vertebrate taxa including fish. With a growing number of researchers working on fish in the field and expanding mandates of IACUCs to regulate field work, there is potential for interactions between aquatic biologists and IACUCs to result in unexpected challenges and misunderstandings. Here we raise a number of issues often encountered by researchers and suggest that they should be taken into consideration by IACUCs when dealing with projects that entail the examination of fish in their natural environment or other field settings. We present these perspectives as ten practical realities along with their implications for establishing IACUC protocols. The ten realities are: (1) fish are diverse; (2) scientific collection permit regulations may conflict with IACUC policies; (3) stakeholder credibility and engagement may constrain what is possible; (4) more (sample size) is sometimes better; (5) anesthesia is not always needed or possible; (6) drugs such as analgesics and antibiotics should be prescribed with care; (7) field work is inherently dynamic; (8) wild fish are wild; (9) individuals are different, and (10) fish capture, handling, and retention are often constrained by logistics. These realities do not imply ignorance on the part of IACUCs, but simply different training and experiences that make it difficult for one to understand what happens outside of the lab where fish are captured and not ordered/purchased/reared, where there are engaged stakeholders, and where there is immense diversity (in size, morphology, behaviour, life-history, physiological tolerances) such that development of rigid protocols or extrapolation from one species (or life-stage, sex, size class, etc.) to another is difficult. We recognize that underlying these issues is a need for greater collaboration between IACUC members (including veterinary professionals) and field researchers which would provide more reasoned, rational and useful guidance to improve or maintain the welfare status of fishes used in field research while enabling researchers to pursue fundamental and applied questions related to the biology of fish in the field. As such, we hope that these considerations will be widely shared with the IACUCs of concerned researchers

Visual and Chemical Prey Cues as Complementary Predator Attractants in a Tropical Stream Fish Assemblage

To date, little attention has been devoted to possible complementary effects of multiple forms of public information similar information on the foraging behaviour of predators. In order to examine how predators may incorporate multiple information sources, we conducted a series of predator attraction trials in the Lower Aripo River, Trinidad. Four combinations of visual (present or absent) and chemical cues (present or absent) from each of two prey species were presented. The occurrences of three locally abundant predatory species present within a 1 m radius of cue introduction sites were recorded. The relative attractiveness of cue type to each predator was directly related to their primary foraging modes, with visual ambush predators demonstrating an attraction to visual cues, benthivores to chemical cues, and active social foragers demonstrating complementary responses to paired cues. Predator species-pair counts were greatest in response to cues from the more abundant prey species, indicating that individuals may adopt riskier foraging strategies when presented with more familiar prey cues. These differences in predator attraction patterns demonstrate complementary effects of multiple sensory cues on the short-term habitat use and foraging behaviour of predators under fully natural conditions