Evidence of social communities in a spatially structured network of a free-ranging shark species

Summary 1. There has been considerable debate over the past decade with respect to wildlife provisioning, especially resultant behavioural changes that may impact the ecological function of an apex predator. The controversy is exemplified by the shark diving industry, where major criticisms based on inference, anecdote and opinion stem from concerns of potential behaviourally mediated ecosystem effects because of ecotourism provisioning (aka ‘chumming’ or feeding). 2. There is a general lack of empirical evidence to refute or support associated claims. The few studies that have investigated the behavioural impacts of shark provisioning ecotourism have generated conflicting conclusions, where the confidence in such results may suffer from a narrow spatial and temporal focus given the highly mobile nature of these predators. There is need for studies that examine the potential behavioural consequences of provisioning over ecologically relevant spatial and temporal scales. 3. To advance this debate, we conducted the first satellite telemetry study and movement analysis to explicitly examine the long-range migrations and habitat utilization of tiger sharks (Galeocerdo cuvier) originating in the Bahamas and Florida, two areas that differ significantly with regards to the presence ⁄ absence of provisioning ecotourism. 4. Satellite telemetry data rejected the behaviourally mediated effects of provisioning ecotourism at large spatial and temporal scales. In contrast, to the restricted activity space and movement that were hypothesized, geolocation data evidenced previously unknown long-distance migrations and habitat use for both tiger shark populations closely associated with areas of high biological productivity in the Gulf Stream and subtropical western Atlantic Ocean. We speculate that these areas are likely critically important for G. cuvier feeding forays and parturition. 5. We concluded that, in the light of potential conservation and public awareness benefits of ecotourism provisioning, this practice should not be dismissed out of hand by managers. Given the pressing need for improved understanding of the functional ecology of apex predators relative to human disturbance, empirical studies of different species sensitivities to disturbance should be used to guide best-practice ecotourism policies that maximize conservation goals.

https://besjournals.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2435.2012.01973.x

Don't bite the hand that feeds: assessing ecological impacts of provisioning ecotourism on an apex marine predator

Not since F. R. Harden Jones published his masterwork on fish migration in 1968 has a book so thoroughly demystified the subject. With stunning clarity, David Hallock Secor's Migration Ecology of Fishes finally penetrates the clandestine nature of marine fish migration. Secor explains how the four decades of research since Jones' classic have employed digital-age technologies-including electronic miniaturization, computing, microchemistry, ocean observing systems, and telecommunications-that render overt the previously hidden migration behaviors of fish. Emerging from the millions of observed, telemetered, simulated, and chemically traced movement paths is an appreciation of the individual fish. Members of the same populations may stay put, explore, delay, accelerate, evacuate, and change course as they conditionally respond to their marine existence. But rather than a morass of individual behaviors, Secor shows us that populations are collectively organized through partial migration, which causes groups of individuals to embark on very different migration pathways despite being members of the same population. Case studies throughout the book emphasize how migration ecology confounds current fisheries management. Yet, as Secor explains, conservation frameworks that explicitly consider the influence of migration on yield, stability, and resilience outcomes have the potential to transform fisheries management. A synthetic treatment of all marine fish taxa (teleosts and elasmobranchs), this book employs explanatory frameworks from avian and systems ecology while arguing that migrations are emergent phenomena, structured through schooling, phenotypic plasticity, and other collective agencies. The book provides overviews of the following concepts: the comparative movement ecology of fishes and birds; the alignment of mating systems with larval dispersal; schooling and migration as adaptations to marine food webs; Natal homing; connectivity in populations and metapopulations; and, the contribution of migration ecology to population resilience.

Migration Ecology of Marine Fishes

There are widespread records of grouping behaviour in both adult and juvenile sharks and rays (Class Chondrichthyes, Subclass Elasmobranchii). Yet despite burgeoning descriptions of these events, many of the proximate and ultimate causes of group living in these top predators remain elusive. Given the documented negative anthropogenic effects on many shark populations globally, there is an increasing need to understand how behaviourally mediated grouping influences population distributions and abundance, and the role this plays in exacerbating vulnerability to fishing mortality. Here, we analyse group living in elasmobranchs: we describe our current understanding of the patterns, mechanisms and functions of both aggregation (where grouping is not driven by social mechanisms) and social grouping (where grouping is influenced by social interaction) and discuss some of the current methods used to study social behaviour in this taxa. In particular, social preferences in elasmobranchs have received relatively little attention. We propose that the study of shark aggregations may benefit from a more fine-scale analytical approach offered by detailed exploration of social interactions using social network analysis. Better understanding of the frequency and longevity of social relations, in conjunction with current long-term data on habitat use and site philopatry, will likely serve for a more informed approach to coastal and pelagic elasmobranch conservation initiatives.

Social behaviour in sharks and rays: analysis, patterns and implications for conservation

https://sharkresearch.rsmas.miami.edu/wp-content/uploads/2015/03/Gallagher-et-al.-2015-Tourism.pdf

Biological effects, conservation potential, and research priorities of shark diving tourism.

The role of learning in behaviour is well known for many animal taxa, including teleost fishes, insects, birds and mammals. However, its importance to sharks in everyday behavioural processes has rarely been considered. Almost 50 years ago the first learning experiments on sharks were conducted; our first section discusses these studies and places them in a framework of associative and non-associative learning. These experiments showed that sharks were capable of different forms of learning, such as operant and classical conditioning and habituation. Sharks could learn associations as rapidly as other vertebrates and also remember training regimes for several months. However, much of this experimental evidence was based on small sample sizes and few shark orders, such as Carcharhiniformes and Orectobliformes, leaving large gaps in our knowledge of the general learning capabilities of other shark orders. We also examine recent research that has tested for, or inferred learning in behavioural processes. This section reveals that sharks, like teleost fishes use learning to improve prey search and capture to potentially navigate and orientate in their home range and recognize conspecifics, heterospecifics and mates. Learning is also discussed in relation to ecotourism and fisheries. Findings indicated that these activities may lead to conditioning of sharks and that considerable effort should go into investigating what impact this could have on the shark species involved. Finally, we discuss the importance of combining laboratory experiments with field studies, the use of new experimental techniques, the role of model species and research priorities for future work.

The role of learning in shark behaviour

The expanding shark fin market has resulted in intensive global shark fishing and with 90% of teleost fish stocks over-exploited, sharks have become the most lucrative target. As predators, they have high ecological value, are sensitive to fishing pressure, and are in decline, but the secretive nature of the fin trade and difficulties obtaining relevant data, obscure their true status. In consumer countries, shark fin is a luxury item and rich consumers pay high prices with little interest in sustainability or legal trade. Thus, market demand will continue to fuel the shark hunt and those accessible to fishing fleets are increasingly endangered. Current legal protections are not working, as exemplified by the case of the shortfin mako shark, and claims that sharks can be sustainably fished under these circumstances are shown to be misguided. In the interests of averting a catastrophic collapse across the planet’s aquatic ecosystems, sharks and their habitats must be given effective protection. We recommend that all sharks, chimaeras, manta rays, devil rays, and rhino rays be protected from international trade through an immediate CITES Appendix I listing. However, a binding international agreement for the protection of biodiversity in general is what is needed.

/pdf/shark-fishing-vs-conservation-analysis-and-synthesis-vk4w4g2o.pdf

Shark Fishing vs. Conservation: Analysis and Synthesis


Reef sharks, including blackfins (Carcharhinus melanopterus) reside in the lagoons and on the outer slopes of the barrier reefs of Mo’orea Island, French Polynesia. In general the lagoons are shallow enough to permit underwater observation, while dive clubs hold shark dives at different sites in the lagoons and in the ocean. Thus, the presence of blackfin sharks especially, and other species at times, is confirmed daily. Between about 21 July and 2 August 2002, all blackfin reef sharks under observation, and possibly some of the other species, left their lagoon and ocean ranges and disappeared from human view, a unique evacuation for which no explanation was found. The event suggests an unknown pattern or influence at work which was perceived by sharks, but was not apparent to those investigating.

https://brill.com/downloadpdf/journals/beh/aop/article-10.1163-1568539X-bja10198/article-10.1163-1568539X-bja10198.pdf

Shark evacuation from Mo’orea island in 2002


In this review of the behavioural patterns of chondrichthyan fishes, we have strived to produce a comprehensive catalogue of events and states and develop standardized terminology. Hence, actions that are slightly different, will be pooled under inclusive titles. Those used by different investigators are included in quotations within the textual descriptions of the motor patterns. This standardized ethogram will ideally lead to an increase in inter-observer reliability, giving researchers more confidence when reading colleagues’ papers that report behaviours that appear similar to theirs despite being described for different species. The descriptions are presented under the following categories: (1) maintenance (2) courtship (3) filter feeding (4) scavenging (5) predation (6) sociality (7) aggression and (8) defence. The many actions are illustrated by line drawings and photographs in composite figures with an attempt to provide an example of each action for a chimaera, shark, and ray. The diversity of patterns is evident from this ethogram, consistent with observation that the brain-to-body mass ratios of cartilaginous fishes are greater than a third of the bird species and greater than those for some mammalian species. The major impetus for assembling this ethogram is to demonstrate the diversity of behaviours exhibited by members of the Chondrichthyes and to dispel the apocryphal belief that members of this taxon are ‘simple feeding machines’.

A review of the behaviours of the Chondrichthyes: a multi-species ethogram for the chimaeras, sharks, and rays

The market for shark fin soup, a fashionable, high-end Chinese dish, has resulted in intensive shark fishing across all oceans. At the same time, 90% of teleost fish stocks are over-exploited, making sharks the most lucrative target: fisheries that have not previously hunted them are now. As top and middle predators, sharks have high ecological value and poor capacity to withstand fishing mortality, but though their numbers are plummeting, the secretive nature of the fin trade, along with the difficulties of obtaining relevant data, obscure their true status. In consumer countries, shark fin is a luxury item and rich consumers are willing to pay high prices. There is little interest in sustainability or legal trade. Thus market demand will continue to fuel the search for sharks and those accessible to fishing fleets are increasingly endangered. Current legal protections are not working, as is clearly seen in the case of the shortfin mako. Claims that sharks can withstand such targeted, industrial hunting and be sustainably fished under these circumstances are shown to be misguided. In the interests of averting a catastrophic collapse across the planet’s aquatic ecosystems, sharks must be given effective protection. We recommend that all sharks, chimaeras, manta rays, devil rays, and rhino rays be protected from international trade through an immediate CITES Appendix I listing. However, a binding international agreement for protection, not only of sharks, but of the loss of biodiversity in general, is what is most needed to allow marine and fresh water ecosystems to recover.

Ila F Porcher

Papers

The role of learning in shark behaviour

Shark Fishing vs. Conservation: Analysis and Synthesis

Shark evacuation from Mo’orea island in 2002

A review of the behaviours of the Chondrichthyes: a multi-species ethogram for the chimaeras, sharks, and rays

Shark conservation: Analysis and synthesis