Paul J. B. Hart

Quorum decision-making facilitates information transfer in fish shoals

Despite the growing interest in collective phenomena such as “swarm intelligence” and “wisdom of the crowds,” little is known about the mechanisms underlying decision-making in vertebrate animal groups. How do animals use the behavior of others to make more accurate decisions, especially when it is not possible to identify which individuals possess pertinent information? One plausible answer is that individuals respond only when they see a threshold number of individuals perform a particular behavior. Here, we investigate the role of such “quorum responses” in the movement decisions of fish (three-spine stickleback, Gasterosteus aculeatus). We show that a quorum response to conspecifics can explain how sticklebacks make collective movement decisions, both in the absence and presence of a potential predation risk. Importantly our experimental work shows that a quorum response can reduce the likelihood of amplification of nonadaptive following behavior. Whereas the traveling direction of solitary fish was strongly influenced by a single replica conspecific, the replica was largely ignored by larger groups of four or eight sticklebacks under risk, and the addition of a second replica was required to exert influence on the movement decisions of such groups. Model simulations further predict that quorum responses by fish improve the accuracy and speed of their decision-making over that of independent decision-makers or those using a weak linear response. This study shows that effective and accurate information transfer in groups may be gained only through nonlinear responses of group members to each other, thus highlighting the importance of quorum decision-making.

Correlates of boldness in three-spined sticklebacks (Gasterosteus aculeatus)

Behavioural variation is known to occur between individuals of the same population competing for resources. Individuals also vary with respect to their boldness or shyness. An individual’s position along the shy-bold axis may be defined as the extent to which it is willing to trade off potentially increased predation risks for possible gains in resources. Similarly, group living may be interpreted as a trade-off between anti-predatory tactics and foraging efficiency. The responses of three-spined sticklebacks (Gasterosteus aculeatus) were tested across four social contexts to assess relative boldness or shyness and to further examine whether their behaviour would be consistent within and between contexts. Individuals displayed consistent responses within and between the first two contexts: those individuals which resumed foraging rapidly after a simulated aerial predator attack also displayed low shoaling tendencies. Such fish were deemed to be bold, whilst those which displayed the converse behaviour, slow resumption of foraging and a high shoaling tendency, were deemed to be shy. In a third context, bold individuals out-competed shy conspecifics for food. Boldness was also positively correlated with growth over a 6-week period. The position adopted by an individual within a group is usually interpreted as a trade-off between predation risk and foraging efficiency—both are greater at the front of a mobile group. Bold individuals showed significantly stronger tendencies towards front positions than shy conspecifics. The results suggest that, contrary to some previous studies on other animals, bold or shy behaviour in sticklebacks is consistent between contexts.

Seamounts: Ecology, Fisheries & Conservation

1 Seamount characteristics. Paul Wessel. 2 How many seamounts are there and where are they located?. Adrian Kitchingman, Sherman Lai, Telmo Morato and Daniel Pauly. 3 A history of seamount research. Paul E. Brewin, Karen I. Stocks and Gui Menezes. 4 Physical processes and seamount productivity. Martin White, Igor Bashmachnikov, Javier Aristegui and Ana Martins. 5 Seamount plankton dynamics. Amatzia Genin and John F. Dower. 6 Midwater fish assemblages and seamounts. Filipe M. Porteiro and Tracey Sutton. 7 Seamount benthos. Sarah Samadi, Thomas Schlacher and Bertrand Richer de Forges. 8 Corals on seamounts. Alex D. Rogers, A. Baco, H. Griffiths, T. Hart and Jason M. Hall-Spencer. 9 Seamount fishes: ecology and life histories. Telmo Morato and Malcolm R. Clark. 10 Fish visitors to seamounts. Section A: Tunas and billfish at seamounts. Kim N. Holland and R. Dean Grubbs. Section B: Aggregations of large pelagic sharks above seamounts. Feodor Litvinov. 11 Seamounts and cephalopods. Malcolm Clarke. 12 Air-breathing visitors to seamounts. Section A: Marine mammals. Kristin Kaschner. Section B: Sea turtles. Marco A. Santos, Alan B. Bolten, Helen R. Martins, Brian Riewald and Karen A. Bjorndal. Section C: Importance of seamounts to seabirds. David R. Thompson. 13 Biogeography and biodiversity of seamounts. Karen I. Stocks and Paul J.B. Hart. 14 Raiding the larder: a quantitative evaluation framework and trophic signature for seamount food webs. Tony J. Pitcher and Cathy Bulman. 15 Modelling seamount ecosystems and their fisheries. Beth Fulton, Telmo Morato and Tony J. Pitcher. 16 Small-scale fishing on seamounts. Helder Marques da Silva and Mario Rui Pinho. 17 Large-scale distant-water trawl fisheries on seamounts. Malcolm R. Clark, Vladimir I. Vinnichenko, John D.M. Gordon, Georgy Z. Beck-Bulat, Nikolai N. Kukharev and Alexander F. Kakora. 18 Catches from world seamount fisheries. Reg Watson, Adrian Kitchingman and William Cheung. 19 Impacts of fisheries on seamounts. Malcolm R. Clark and J. Anthony Koslow. 20 Management and conservation of seamounts. P. Keith Probert, Sabine Christiansen, Kristina M. Gjerde, Susan Gubbay and Ricardo S. Santos. 21 The depths of ignorance: an ecosystem evaluation framework for seamount ecology, fisheries and conservation. Tony J. Pitcher, Telmo Morato, Paul J.B. Hart, Malcolm R. Clark, Nigel Haggan and Ricardo S. Santos

The impact of species changes in African lakes

Contributors. Series Foreword. Preface. General Introduction. Species change and fisheries in African Lakes: outline of the issues. Part One:- introduced Nile perch in Lake Victoria: Impacts on biodiversity and evaluation of the fishery: Impact of environmental change, species introductions and ecological interactions on the fish stocks of Lake Victoria. Limnological changes in Lake Victoria since the Nile perch introduction. Impact of fish species introductions on the tilapias of Lake Victoria and Kyoga. Diversity and stability of fish stocks in Lake Victoria, Kyoga and Nabugabo after establishment of introduced species. Dynamics of the haplochromine cichlid fauna and other ecological changes in the Mwanza Gulf of Lake Victoria. An analysis of species change in Lake Victoria: did the Nile perch act alone?. Analysis of species change in Lake Victoria using ECOPATH, a multispecies trophic model. Assessment of the Nile perch fishery in Lake Victoria. Thirty years on: the development of the Nile perch fishery in Lake Victoria. Socio-economic impacts of introduced species in Lake Victoria fisheries. Part Two:- evaluation of species change in other African lakes with introduced fish species: Inshore fish population and species changes in Lake Kariba, Zimbabwe. The impact of an introduction of sardine into Lake Kivu. The persistence of two introduced tilapia species in Lake Naivasha, Kenya, in the face of environmental variability and fishing pressure. Species change in reservoir fisheries following impoundment: the case of Lake Itezhi-tezhi, Zambia. Part Three:- evaluation of species changes in African lakes without introduced species: Changes in species composition and abundance of fish populations in Lake Turkana, Kenya. Management, conservation and species changes of exploited fish stocks in Lake Malawi. Changes in demersal cichlid communities as a result of trawling in southern Lake Malawi. Changes in species composition and abundance as a consequence of fishing in Lake Malombe, Malawi. Effects of exploitation on the pelagic fish community in the south of Lake Tanganyika. Changes in the pelagic fisheries of northern Lake Tanganyika during the 1980s. Part Four:- overviews of fish introductions in African Lakes: Genetic impacts of fish introductions: a perspective on African lakes. Fish introductions in the African Greak Lakes: some special characteristics. Thinking th unthinkable: a candidate model for predicting sustainable yields of introduced fish species in African lakes. Why is Limnothrissa miodon such a successful introduced species and is there anywhere else we should put it? Appendix: summary of characteristics of major African lakes. Author index. Species index. Subject index.

Boldness is influenced by social context in threespine sticklebacks (Gasterosteus aculeatus)

Summary Boldness refers to the extent to which animals balance risk against benefits when engaging in such behaviors as foraging, exploration or resource competition. Evidence suggests that individuals can behave strategically, acting boldly in situations when doing so is adaptive, whilst avoiding risk when the rewards are correspondingly lower. In this study we sought to determine the effects of social context upon the boldness of threespine sticklebacks (Gasterosteus aculeatus). We found that when individuals were tested alone, those that were more active were more likely to resume foraging sooner when subjected to a simulated predator attack in a separate test, and also consumed more prey in foraging competition trials. We found no effect of group size upon the relative ability of individuals to effectively compete for prey. Group size did affect other behaviours however: focal fish were more active and resumed foraging more rapidly when tested in groups that they did when tested alone. Finally, individual social information use was not correlated with behaviour in other contexts. Two competing hypotheses, the adaptation and the constraint hypotheses have been posited to explain the presence and prevalence of individual variation in boldness; our findings offer partial support for the former of these.

Pike as a selective predator. Effects of prey size, availability, cover and pike jaw dimensions

An experiment was performed to study the influence of prey size, availability, the presence or absence of cover and pike jaw dimensions on prey consumption by pike. Rudd in schools of 10 were offered to pike in outdoor pools. Pike weighed between 66.4 and 182.1 g. Schools of 10 rudd contained two, five or eight fish with mean sizes between 5.6 and 6.8 g, the remaining fish weighing between means of 12.4 and 14.1 g. Cover was provided by a 1 m2 mat of plastic netting supporting simulated plant stems spaced at 5 cm intervals. Pike chose mostly from the small size category and the presence of cover did not significantly influence the choice made. Increased availability of the chosen prey size increased food intake. Pike never completely dropped the large prey from the diet despite its low availability; a case of partial preference. The jaw dimensions of the pike were most closely correlated with the body dimensions of the small rudd. It is suggested that the prey size eaten was determined by an interaction between pike jaw morphology and the relative swimming speeds of pike and rudd, rather than by a behavioural choice.

Social recognition in wild fish populations.

The ability of animals to gather information about their social and physical environment is essential for their ecological function. Odour cues are an important component of this information gathering across taxa. Recent laboratory studies have revealed the importance of flexible chemical cues in facilitating social recognition of fishes. These cues are known to be mediated by recent habitat experience and fishes are attracted to individuals that smell like themselves. However, to be relevant to wild populations, where animals may move and forage freely, these cues would have to be temporally flexible and allow spatial resolution. Here, we present data from a study of social recognition in wild populations of three-spined sticklebacks (Gasterosteus aculeatus). Focal fish preferentially associated with conspecifics from the same habitat as themselves. These preferences were changed and updated following translocation of the focal fish to a different site. Further investigation revealed that association preferences changed after 3 h of exposure to different habitat cues. In addition to temporal flexibility, the cues also allowed a high degree of spatial resolution: fish taken from sites 200 m apart produced cues that were sufficiently different to enable the focal fish to discriminate and associate with fish captured near their own home site. The adaptive benefits of this social recognition mechanism remain unclear, though they may allow fish to orient within their social environment and gain current local information.

Voluntary management in an inshore fishery has conservation benefits

SUMMARY The management of fisheries in European Union (EU) waters has generally been regulated through government institutions and agreed quota allocations. This top-down management approach may have contributed to the continued decline of targeted fish stocks by forcing fishers to compete for limited resources without engendering a sense of resource stewardship. In attempting to reverse this decline, scientists and managers should examine management systems that do not solely depend on top-down approaches, and the Inshore Potting Agreement (IPA) is an example. The IPA is a voluntary fishery management system designed and operated by inshore fishers of south Devon, England. The IPA was conceived to reduce conflict between static-gear (pot and net) and towed-gear (trawl and dredge) fishers, and is regarded as a successful fisheries management regime by fishers and managers because it has effectively allowed fishers from both sectors to operate profitably on traditional fishing grounds. Another study determined that the IPA has incidentally protected benthic habitat complexity. Fishers from the static-gear and towed-gear sectors were interviewed to determine the evolution and function of the IPA, and to establish the factors that ensure the high level of regulatory compliance amongst fishers from both sectors. Towed-gear fishers gave significantly different responses to the same questions asked of static-gear fishers, and were generally less satisfied with the existence of the IPA. Multivariate analyses of the interview data suggested that fishers who thought the IPA was a good system also thought the system provided pot protection, but had experienced inter-sector conflict. Fishers who thought the IPA provided no personal benefit also thought that static-gear fishers should be more restricted, and that towed-gear corridors or more seasonal-use areas should be established within the existing IPA area. However, fishers from both sectors agreed that the IPA has maintained traditional practices of the local fishing industry, and that the system has conserved target finfish and scallop species. A number of factors were identified as critical to the success of the IPA. These included the voluntary nature of the agreement, the limited number of organizations representing fishers and very high level of membership of those organizations, and the simplicity of the system. Regulatory compliance is enhanced through the ability of fishers’ organizations to respond rapidly to inter-sector conflict issues.

Habitat-specific chemical cues influence association preferences and shoal cohesion in fish

The structure of social animal groups can be dynamic, characterized by high rates of group fission and fusion. Despite this, group composition is often well ordered by factors such as species, body size and by numerous other phenotypic traits. Research in shoaling fishes has revealed that individuals refine group membership decisions still further and are capable of assimilating chemical cues pertaining to recent habitat and prey use by prospective group mates, preferring to associate with others whose recent resource use history closely matches their own. In this study, we firstly examined the dynamics of the formation and breakdown of these preferences, revealing that they can be acquired and replaced in a matter of just a few hours. Using such cues enables individuals to accurately assess the resource use of conspecifics, allowing them to indirectly sample the local environment while reducing the chances of acquiring outdated information that can precipitate maladaptive behaviors. Secondly, we found that shoals composed of individuals with shared recent habitat use history were more cohesive compared to those where the constituent individuals differed in recent habitat use. Increased shoal cohesion may reduce predation risk, and could enhance the ability of individuals to detect and use social information.

Turbidity and foraging rate in threespine sticklebacks: The importance of visual and chemical prey cues

In aquatic habitats turbidity can affect the foraging efficiency of visual predators, directly influencing their capacity to detect prey. In a laboratory study we tested the effect of different loads of suspended sediment upon the foraging rates of threespine sticklebacks (Gasterosteus aculeatus). We compared the foraging rates of fish under a series of different turbidity treatments, testing fish originating from four habitats within a single drainage basin that differed in a number of environmental parameters including turbidity. Although we found habitat specific differences in foraging rates, these did not correspond to local turbidity levels. The findings of a follow up experiment revealed habitat-specific variation in boldness, which may be indirecly linked to the observed differences in foraging rate. The main finding of our study was that turbidity alone had no impact upon their prey capture rates, but that high turbidity in combination with saturation with prey odour extract caused prey capture rates to fall significantly. This suggests that olfactory cues can be more important than visual cues in determining foraging performance in this species, potentially influencing how they cope with naturally occurring periods of turbidity, and how they adapt to human-induced eutrophication.