Tuesday 29 June 2010
Sharks are little understood creatures. Scientists know little about their secretive lives in comparison to many land dwelling species, so when the world's top minds the field of shark science come together, it's an important event. Cheryl-Samantha Owen Ocean Correspondant for the Save Our Seas Foundation reports back on the Sharks International conference.
Sharks International, the first international shark conference in 20 years, brought together over 200 delegates from 23 countries to present the latest in shark science. It provided a forum for the world’s leading shark and ray experts, along with students and researchers, to come together to share ideas, update information and report on the progress of the most recent scientific studies in the field of shark and ray ecology. The evolution of some key technologies has been a considerable driving force behind the advancement of knowledge of shark behaviour over the past 25 years. As these species become more affected by human environmental factors on a global scale, international approaches to their study and management will be increasingly important.
The Save Our Seas Foundation, along with other organistions such as the Australian Government and James Cook University, sponsored the event. Thirteen scientists supported by the Save Our Seas Foundation presented cutting edge research in fields ranging from telemetry studies focusing on the movement patterns of sharks and the use of portable field kits for measuring stress levels in sharks to the genetic analysis of shark fins and the current status of shark conservation.
Dr Rupert Ormond, Chief Scientist of the SOSF, presented his findings on how some individuals buck the trend of recorded movement pattern. It appears some individual basking sharks, white sharks and whale sharks in the NE Atlantic, South Africa and the Seychelles respectively take the pass less traveled between feeding grounds and appear to be resident in feeding areas for different lengths of time, while the majority stick to a particular route and pattern. Perhaps as a youngster those individuals were exposed to different currents or water temperatures, which led them on their unique journey and they have simply stuck to it over the years. SOSF is still trying to solve the mystery.
Following on from this Alison Kock from the SOSF Shark Centre in Cape Town presented her work on the year-round white shark presence in False Bay, South Africa with distinct seasonal changes in habitat utilization. Her work highlighted that even though white sharks are fully protected in South Africa, there are many issues such as bycatch, poaching, impact of shark bites, habitat, prey loss and pollution that still affect these sharks.
Sharks have feelings too… and they get stressed! Stressed to death in some cases. Several scientists presented their results on how sharks fare after being hung in the open ocean by a long lining hook – dragged along the sea floor in a trawler’s net or left by fishermen on a boat slowing suffocating before being thrown back into the sea. Sharks may have evolved over the past 400 million years – but they didn’t come equipped to deal with modern fishing torture techniques.
Sharks are global travellers and observing them in the wild is no easy task. The biggest change to shark behaviour research arrived with the advent of acoustic and satellite telemetry. These technologies, which use tags to record a wide array of sensory data, enable scientists to track the exact locations of where individual sharks travel and the temperature, depth, and light levels that they experience on their journeys. Through telemetry scientists have expanded our knowledge of movement patterns, feeding and mating behaviour, as well as an understanding of the physiology that drives these behaviours. There has been a growing trend in the number of scientists using telemetry technology and over 20 per cent of the talks at the conference include the use of telemetry. Blacktip reef sharks, whitetip reef sharks, whiptail stingrays in the Amazon estuary, shovelnose guitarfish, manta rays, bull sharks, blue sharks, whale sharks and white sharks are just some of the species fitted with tags, which are well on their way to revealing just exactly what they get up to when scientists aren’t looking.
SOSF scientist Dr. Andrea Marshall (also known as the Manta Queen, from the 2009 BBC documentary) presented her work on seven years of observations of the size, population structure and migratory behaviour of the newly described giant manta ray (Manta birostris). From her base in southern Mozambique Dr. Marshall has identified over 130 individuals at an inshore aggregation site, which supports both feeding areas and cleaning stations. Preliminary data from two satellite tagged individuals have demonstrated that the species is capable of international migration – a crucial consideration for future regional management plans. As well as discovering the species Dr. Marshall has also discovered that this manta is one of the deepest diving fish in the sea.
Dr. Jeurg Brunnschweiler later revealed his results on the small-scale movement patterns of bull sharks in the Shark Reef Marine Reserve off the southern coast of Viti Levu, Fiji. More than 60 bull sharks fitted with acoustic tags collected this data, while 14 pop-up satellite archival tags were deployed between 2004 and 2009 to monitor the movement of bull sharks away from Shark Reef and their passage through the water column.
One of the biggest difficulties in fisheries management is the widespread distribution of most species and the fact that sharks don’t acknowledge international boundaries. Dr. Shivji, based at the Save Our Sea Shark Research Centre and Guy Harvey Research Institute in Florida, USA, gave a “first-look” analysis of population genetic structure in sharks. He revealed that nearly all species of sharks with global distributions have different inter-ocean basis populations and distinct genetic population structure has also been detected within ocean basins. In fact, the scale of some populations may be on an even smaller geographic scale, meaning the sharks in a specific location may belong to their own genetic population. These discoveries are an important conservation flag. The major significance of these findings is being able to assess and manage sharks on a population-specific basis. The number of species in one area might be healthy, but elsewhere that same species may be in danger of extinction, and because they are genetically distinct populations the healthy populations won’t fill the gap of a population that is fished off our planet. “Over the last five years we have discovered through genetic research that the population structures of sharks are different to what we use to assume. This information needs to be used by management bodies to help conserve shark populations,” says Dr. Shivji.
Other talks illustrated how research on the big fauna, such as whale and basking sharks, leads to better protection of the web of life that surrounds them. Dr. Mauvis Gore discussed the ‘Ups and downs of being a megaplanktivore’ by illustrating how both basking and whale sharks dive in a number of distinctive patterns, including V-shaped spikes, W-shaped sawtooth and oscillatory staircasing! - in search of prey. Deni Ramirez-Macias covered her work on whale shark population size and structure in La Paz Bay, Mexico, and David Rowat presented some interesting observations on the long term residence in coastal aggregations of whale shark in Seychelles and Djibouti.
In the beginning shark behaviour research resulted from the need to answer, “How can we protect humans from sharks?” The tide has since turned and, with as many as 73 million sharks killed each year, today we are all asking, “How can we protect sharks from humans?” Collecting and analyzing all this data is a giant step towards providing some answers to this question. Shark filming legends Ron and Valerie Taylor, who attended the conference, were once champion spear-fishermen before they turned into marine and shark life advocates. “Marine life belongs to all of us, not just the fishermen, and we should be able to see them (the sharks and other fish) anytime we want,” said Valerie.
Contact: Cheryl-Samantha Owen
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