Shark

PROJECT TITLE: Auditory abilities of sharks and their relatives

RESEARCHERS: Prof. Shaun Collin, A/Prof. Robert McCauley, A/Prof. Nathan Hart and Lucille Chapuis
LOCATION: University of Western Australia

OVERVIEW

Sharks are subjected to intense fishing pressures worldwide and their numbers are being decimated, notably due to bycatch and entanglements in beach nets. Finding alternatives to the culling of sharks is crucial for the continued conservation of these iconic megafauna.

Determining hearing thresholds of sharks and their relatives (i.e. frequencies and intensities) is vital in assessing how natural and anthropogenic noise affects natural behaviours. A possible outcome of this behavioural research will include the development of a shark acoustic repellent device at both personal and beach-based levels.

The elasmobranch taxa (sharks, rays and skates) use hearing to process information about approaching predators, the location of food and potential mates, compass bearings for migration and their position in space. These early vertebrates also hold keys to the series of events that have led to the evolution of our own sensory systems.

Although fish audiograms (graphic displays of a hearing test) have been obtained for only 10 of approximately 500 species of the elasmobranch taxa, recent studies in their laboratory have revealed high inter-specific diversity of the inner ear structures from species from different environments 1,2. Exploring those patterns, linking the functional structure to the ecology of sharks and rays, understanding interactions of these species with their habitat, and promoting better conservation management are the fundamental objectives for this study.

Examining all the different components of the auditory apparatus in a variety of species will identify both ecological and phylogenetic influences on the evolution of the inner ear. This same approach will also allow us to determine whether hearing abilities may change over a species’ lifecycle, especially in species like sharks that are known to alter their habitat as they mature.

REFERENCES:

1. EVANGELISTA, Carla, MILLS, Morena, SIEBECK, Ulrike E. & COLLIN, Shaun P. (2010) A Comparison of the External Morphology of the Membranous Inner Ear in Elasmobranchs, JOURNAL OF MORPHOLOGY 271:483–495

2. MILLS, Morena, RASCH, Ron, SIEBECH, Ulrike E. & COLLIN, Shaun P (2011) Exogenous Material in the Inner Ear of the Adult Port Jackson Shark, Heterodontus portusjacksoni(Elasmbranchii) THE ANATOMICAL RECORD 294:373–37

PROJECT TITLE: A case of mistaken identity? Why do sharks attack humans?

RESEARCHERS: Nathan Hart
LOCATION: University of Western Australia

OVERVIEW

It has often been suggested that attacks on humans have occurred because they have been mistaken for prey by the shark. For example does a surfer or a swimmer in a black wetsuit resemble a seal when viewed from below? At present, there is no hard evidence to suggest this is the case.

This project will allow researchers to address this question directly by defining the visual cues that are available to the sharks under such scenarios. Importantly, it will allow us to determine what the shark is able to see and what strategies might be used to reduce any visual ambiguity and make a human look less like prey.

An individual’s visual perception of their world combines many cues including motion, colour, depth and form. Sharks rely on their visual systems for predatory behaviour, social behaviour, communication, orientation and navigation (Hart et al., 2006). Although the shark visual system is still poorly understood, there is mounting evidence that they are comparatively well developed and, in some species, vision may be the key sensory modality (Lisney et al., 2007).

This study has quantified the ability of some species of shark to visually detect motion which is important in understanding the behavioural interactions between sharks and their habitat and prey. The quantification has allowed us to develop a virtual shark visual system to examine a visual scene from the perspective of a shark. It will be used to compare the ability of pelagic (open water) and benthic (bottom dwelling) sharks to detect and track prey items against complex, cluttered or moving backgrounds such as a coral. It will also provide insight into the strategies evolved by prey to camouflage themselves from potential shark predators.

LISNEY, T. J., BENNETT, M. B. & COLLIN, S. P. 2007. Volumetric analysis of sensory brain areas indicates ontogenetic shifts in the relative importance of sensory systems in elasmobranchs. Raffles Bulletin of Zoology, 7-15.

HART, N. S., LISNEY, T. J. & COLLIN, S. P. 2006. Visual communication in elasmobranchs. In: LADICH F, C., S. P., MOLLER, P. AND KAPOOR, B. G (ed.) Communication in Fishes. Science Publishers Enfield (NH) and Plymouth (UK): Science Publishers Enfield (NH) and Plymouth (UK).

PROJECT TITLE: Phase I: How many white sharks? Temporal variation of the Australian white shark population assessed using novel genetic techniques

RESEARCHERS: Charlie Huveneers
LOCATION: Flinders University

OVERVIEW

Although shark attacks are rare, they typically evoke a dramatic emotional response from the public and the media. Negative perceptions about sharks and shark attack risks have been identified as one of the barriers for global shark conservation efforts.

In this context, human-shark conflicts pose an urgent challenge worldwide because these conflicts often pit human communities against sharks and against other humans who seek to preserve or restore wildlife populations.

This project will ensure that additional hard data and science is considered into the current debate about white shark abundance, which is essential to the Australian Government when assessing the most suitable shark bite mitigation measure and protected status of the Australian white shark population.

This project directly addresses the question of changes in the population size of white sharks and aims to provide evidence for variation in the size of the Australian white shark population based on genetic comparisons of historical and contemporary samples.

Thanks to funds from the Foundation, researchers were able to travel around Australia to obtain more than 200 samples white shark samples suitable for genetic analysis, sometimes from unexpected places like Alice Springs. In combination with the collection from the CSIRO and samples from research trips at the Neptune Islands, this provides the most exhaustive list of white shark samples from the Australian population totalling samples from over 480 individuals and dating as far back as 1877.

PROJECT TITLE: Arresting shark declines, who’s being killed: A genetic approach to determine catch composition of shark fin fisheries

RESEARCHERS: Adam Stow & Heidi Ahonen
LOCATION: Indonesia and Northern Australia

OVERVIEW

This project is the first attempt at monitoring poaching by determining the origin of landed shark fins.

In 2013 Adam Stow & Heidi Ahonen began investigating population genetic structure of grey reef sharks in Northern Australia and Indonesia. Understanding patterns of gene flow is a necessary step for the development of effective conservation strategies. Specifically, a deep understanding of how connectivity patterns are driven by environmental factors can provide a framework to monitor illegal poaching.

Due to their life history strategies many species of sharks are extraordinarily susceptible to over-fishing and in turn have a high risk of extinction.

This is particularly true of grey reef sharks as they
- don't have many pups
- grow slowly
- become sexually mature later in life
- have a limited range

Modest levels of fishing pressure may cause dramatic declines and even within the Great Barrier Reef Marine Park (the most well managed network of marine reserves in the world) reef shark populations are declining at an alarming rate.

The situation is likely to be worse in Indonesia, where grey reef sharks contribute to approximately 2-3% of a landed shark biomass of approximately 110 000 tonnes.

The geographic database of genotypes that will be produced in this study will provide a framework to determine the geographic origin of catch landed in Indonesia. This will shed light on the extent of poaching occurring as Indonesian fishermen often venture into Australian waters where their fishing is largely unregulated, and where they often target grey reef sharks for their valuable fins.

In the future this technique could be used to monitor international trade of commercially important sharks. 

DEFINITIONS:

Landed: the amount of fish (usually in weight) harvested from the sea and brought to the land. May be different from the catch, which includes the discards.

PROJECT TITLE: Grey Nurse Shark Watch

RESEARCHERS: Dr Carley Kilpatrick, Professor Mike Bennett and Miss Deborah Bowden
LOCATION: Currently east coast of Australia (primarily Queensland and NSW) but hoping to expand to include the west coast grey nurse shark population in 2015

OVERVIEW

The grey nurse shark (Carcharias taurus) is a large fish eating species with a stout body and is coloured grey to grey-bronze dorsally with a paler off-white underbelly and reddish or brownish spots often scattered on the body. There are approximately 20 known critical aggregation sites in NSW and there are estimated to be less than 2000 grey nurse sharks (GNS) on the entire east coast of Australia, one reason this population is Critically Endangered.*

As GNS like to aggregate (hang out) and are often found inshore in shallow water (<1000m and usually less than 30m) it is possible to assess population abundance using scuba divers and photographs. These photographs are taken opportunistically throughout the year and during two annual scheduled surveys to photo-identify and photo-recapture individual sharks (from the unique spot patterns on the sides of each shark).

With the support of Sea World, Grey Nurse Shark Watch (GNS Watch) will conduct a multi-day GNS photographic and visual survey to remote and exposed sites rarely documented by volunteer divers.

GNS Watch seeks, collates, analyses and reports on data provided by our volunteers and researchers and will contribute to six of ten objectives in the 2014 National Recovery Plan (Recovery Plan) for the GNS.

GNS Watch will:

1. For the first time, monitor the numbers of the Australian east coast population of GNS and determine if it is increasing, stable or declining
2. Provide information on their distribution and movements at different stages in their life history
3. Provide data to enable interactions with commercial and recreational fishing gear to be quantified, along with associated injuries and any shark recovery
4. Help to identify new aggregation sites
5. Increase public awareness
6. Importantly, GNS Watch through community and researcher photos will provide good data for management purposes via an open and transparent mechanism that involves interested parties

Grey nurse shark Watch (GNS Watch) is a citizen science research and monitoring program that engages a broad cross-section of our community and ultimately aims to use the data obtained (through our 300 + registered volunteers, 550 Facebook followers and research team) to improve the conservation management of the grey nurse shark (GNS) in Australia and to help the Critically Endangered east coast population to recover.

*Recovery Plan for the Grey Nurse Shark (Carcharias taurus) (2014) Department of the Environment, Australian rel="noopener noreferrer" Government
http://www.environment.gov.au/system/files/resources/91e141d0-47aa-48c5-8a0f-992b9df960fe/files/recovery-plan-grey-nurse-shark-carcharias-taurus.pdf

PROJECT TITLE: Migratory movements and genetic effective population size of leopard sharks Stegostoma fasciatum on the Australian East coast

RESEARCHERS: Christine Dudgeon and Rachel Dunlop
LOCATION: Southern Queensland waters

Leopard sharks (Stegostoma fasciatum) are non-aggressive bottom dwelling sharks. The largest known population is found in southern Queensland coastal waters, with over 460 adult individuals aggregating during the summer months. Researcher Dr Dudgeon and her team initiated a four-year tracking study, tagging 18 of these sharks between February 2012 and April 2013. The sharks are tracked using surgically inserted acoustic transmitters that emit individually recognisable codes. These codes are then detected and decoded by a national coordination of underwater receivers called the Australian Animal Tagging and Monitoring System.

Movement
Leopard sharks in southern Qld and NSW are at the edge of the thermal distribution for this species and investigating movement patterns in relation to water temperature is important for inferring adaptations of species distributions to changing environmental conditions as well as the geographical contribution to a population.

Preliminary results in this study show that:

• during the warmer months the leopard sharks are found off North Stradbroke Island and also move in and out of Moreton Bay with some excursions into more southern waters.
• during the cooler months they move north into warmer waters around the Tropic of Capricorn. This data suggests that the population in southern Queensland travels from at least 800km and up to ~1500km of the East Australian Coastline. One leopard shark moved an unprecedented 2600km from North Stradbroke Island to Orpheus Island off Townsville and back again over six months.

Genetic population size
In this study researchers expanded an existing genetic data set for leopard sharks to compare genetic effective population size (Ne) and census size estimates.

The results showed:

• striking similarities between the estimates, further supporting the use of Ne as tool for shark populations. This is particularly important given that it is difficult to obtain robust size estimates using ecological data for many shark and ray populations. Given that many of these species have conservation concerns, tools to estimate population size are needed.
• by sub sampling our data we were able to show that to obtain clear and consistent Ne estimates, a minimum of 90 samples (approximately 20% of the estimated census size) and 10 genetic marker loci are recommended.

These results provide important guidelines for new studies employing Ne to monitor population size in sharks and rays.

Project Title: Wild shark social networks: impacts of human interventions

Researchers: Culum Brown & Tristan Guttridge
Photo Credit: Justin Gilligan

This project examines the aggregation (grouping) behaviour of the iconic Port Jackson shark.

Surprisingly little is known about these animals other than they aggregate at specific locations along the NSW coastline to breed during the winter and then disappear. Up to 200 sharks can be present at an aggregation site at any one time.

This project involved tagging the sharks in a variety of ways, including: visual tags, proximity tags and acoustic tags, allowing the researchers to identify individuals and track their movements on a range of scales.

So far the data has shown that males arrive at the breeding sites before females. Both males and females appear to show very strong site fidelity and return to the same breeding spot year after year.

The social network analysis has shown that the aggregation is not random; they are hanging out with the same friends. Early results also suggest that males and females have different diets and feed in different habitats.

The nature of social interactions has implications for the transfer of information and disease through populations, as well as influencing a range of other key biological factors such as mating systems, foraging and vulnerability to predation.

PROJECT TITLE: Determining population structure and critical habitat as a means for conserving a key apex predator: the sevengill shark

RESEARCHERS: Adam Barnett
LOCATION: Port Philip Bay, Victoria

The broadnose sevengill sharks (Notorynchus cepedianus) trophic position rivals that of other large sharks such as tiger and white sharks. This large (up to 3m) apex predator is widely distributed in temperate, coastal regions around the world. Yet, despite its ecological importance, relatively little is known about its ecology.

Their low conservation priority may be attributed to the lack of available data (classified as data deficient on the IUCN Red List). For example, in South Africa, scientists have noticed reduced catches, but efforts to form management strategies are hindered by this lack of data.

Recent studies on sevengill sharks in Australia highlighted important gaps in knowledge, specifically:

• the location of breeding, nursery or pupping grounds
• the winter distribution of females, and
• the connectivity between sevengill sharks across the temperate regions of Australia

In order to fill those gaps this research will:
1) determine sevengill shark population structure (size structure and sex ratio) in coastal areas of Victoria, with a focus on Port Philip Bay, a suspected nursery ground
2) identify if Port Philip Bay is a nursery/pupping area or has any other reproductive relevance
3) investigate the connectivity between regions of south-east Australia (Tasmania, Victoria, South Australia and New South Wales). This knowledge is essential to understand and monitor the effects of fishing and changes to coastal habitats for this species.

Such information is crucial for defining stock structure and identifying critical habitats.

DEFINITIONS
Stock structure: the size and sex ratio of subpopulations of a particular species.
Trophic position: the position an organism occupies in a food chain.

PROJECT TITLE: Vision and Light detection in Chondrichthyes

RESEARCHERS: Shaun Collin, Nathan Hart, Eduardo Garza-Gisholt, Kara Yopak & Michael Archer
LOCATION: University of Western Australia

Elephant sharks are a unique species as, unlike all other sharks, many of them migrate from the deep sea where they usually live to shallow waters to reproduce. As they are part of one of the most ancient groups of jawed vertebrates, any research on the chimaeras represents an opportunity to explore the early stages in the evolution of all vertebrates.

This project focused on the structure of the eyes and brain of elephant sharks to understand their visual capabilities and how this is processed within the central nervous system.

The preliminary results of this study show that:

• elephant sharks that venture into shallow water have both cone (bright light) and rod (dim light) photoreceptors in their retina, deep sea chimaeras have rod-only retinas

The eyes of deep sea chimaeras increase their sensitivity to detect objects under low light levels but at the expense of both spatial resolution (indicated by ganglion cell spacing) and the capacity for colour vision. In contrast, the elephant shark that ventures into shallow water has lower sensitivity and the potential for colour discrimination.

Previously published research by this group indicates that:

• the sharks that have been studied have only one type of cone visual pigment enabling them to see only one colour (monochromatic vision) or are colour blind
• some rays and chimaeras have the potential for trichromatic colour vision due to the presence of more than one type of cone visual pigment

The brain detects light used for setting circadian (daily) rhythms via the pineal gland. This area of the brain has been identified and described for the first time in this project. To increase the surface area available to detect light, the surface of the pineal lumen is completely covered by light-absorbing photoreceptor outer segments and has a complex structure.

DEFINITIONS:
Cones: photoreceptors used in bright light conditions.
Circadian rhythms: physical, mental and behavioural changes that follow a roughly 24-hour cycle.
Ganglion cell: a cell type lining the retina in the eye that conveys electrical signals about the image to the visual centres of the brain via the optic nerve.
Pineal gland: small endocrine gland situated on the dorsal surface of the vertebrate brain.
Pineal lumen: Space within the pineal organ into which the light-absorbing photoreceptor cell project.
Retina: a layer at the back of the eyecup that contains nerve cells sensitive to light, which trigger nerve impulses that pass via the optic nerve to the brain, where a visual image is formed.
Rods: sensitive photoreceptors that operate in dim light conditions.
Spatial resolution: the ability to perceive two adjacent objects as being distinct at a set distance.