Impacts of Imperiled Shark Populations

Shark species are increasingly becoming threatened because of commercial and recreational fishing pressures, the impact of non-shark fisheries on the seabed and shark prey species, and other habitat alterations such as damage and loss from coastal development and marine pollution.

Rising demands for shark products has increased pressure on shark fisheries, but little monitoring or management occurs of most fisheries. Major declines in shark stocks have been recorded over the past few decades; some species have declined over 90% and population declines of 70% are not unusual. It is estimated that something like 100 million sharks are killed by commercial and recreational fishing every year.

Is there any hope that an enlightened, forward-looking global management strategy will emerge to help stabilize (or reverse) the imperiled shark species?  Global statistics and regionally objective (and some press and anecdotal) evidence suggest that the answer to this question is an emphatic ”No”.

Despite the efforts of the UNEP, the IUCN (International Union for the Conservation of Nature),  CITES (Commission on International Trade in Endangered Species) and organizations such as the American EPA (Environmental Protection Agency) and fishery management agencies, the last ten years has witnessed no significant reduction in shark depletion numbers.  Does this mean that short-term political, cultural and economic expediency will rule the day into the foreseeable future?  Sadly, all evidence points in that direction.

Of course, there have always been extinctions and the evolution of other (maybe more adaptive) species. However, the rate at which man is influencing these evolutionary changes is unprecedented.  The changes induce a negative ‘cascade’ effect on sub-species, their habitats and food webs.

State of the Affairs

In 2007, the IUCN (Shark Specialist Group) produced a report which concluded that some 30% of the world’s total shark populations faced extinction within the next few decades.  Variability depended on the shark range, reproductive capabilities and fishing and reporting practices.  The percentage increased alarmingly and showed nearer 50% of open water shark species were in some level of endangerment.

With at least 100,000,000 sharks being killed each year (mainly for their fins), this year’s CITES meeting in March concluded that sharks need far better protection if they are to reproduce in sustainable numbers. The major portion of the trade in shark fins is driven by the Asian demand for shark fin soup. The soup is of low nutritional value and the demand is driven by the cultural perception that only shark fin soup can endow social and monetary status via celebratory or luxury functions.

With shark fins attracting an average of $US 400.00/kilo and shark meat attracting less than $US100.00/kilo, it is little wonder that the economics is driving an ever-increasing number of unethical and unscrupulous traders in an increasingly affluent and numerous Asian middle class society.

The current rate of exploitation is clearly unsustainable.  In many parts of the world, the trade remains either unregulated or the existing regulations are not enforced (or remain unenforceable).  It is likely to take decades before effective regulation is introduced and  cultural changes start to have a realistic effect on demand.

Negative Trophic Cascade Impacts

In March 2007, the New York Times reported a 90% reduction in the numbers of hammerhead, duskie and tiger sharks in the Eastern seaboard waters. In the ensuing years, the number of cow-nosed rays (a favorite prey) increased exponentially.  Being a vigorous bottom feeder, they quickly decimated the wild scallop beds along the seaboard and reduced the availability of oysters, clams and other benthic edible species.  The scallop industry collapsed over a two-year period.

The increase in numbers of mid-level prey species was repeated along the Western Seaboard of the USA with similar results over the following 5-year period.  The situation is exacerbated by 11 other mid-level species increasing in numbers to the detriment of the ecology and biodiversity of Atlantic and Pacific Ocean shelf areas.  To a large extent, shell fish farming depends on a good wild stock for replenishment, so farming realistically does not offer a resolution to the problem.

Sadly, the Atlantic Shark Management Plan has proved to be ineffective. There must be a case for improved enforcement procedures along with the introduction of area ecology-based management systems.

Subject-Related Beneficial Trophic Cascades

After a 70-year absence, the grey wolf was reintroduced to Yellowstone Park, Wyoming as the top predator in 1995/6. The last 18 years have witnessed a beneficial trophic cascade impact on Park flora and fauna. Elk populations have stabilized and beavers and bison have returned in sustainable numbers to tree-lined and healthy rivers.  In the absence of over browsing, aspen and cottonwood tree stands benefitted from improved recruitment with the canopy cover developing above the browse level of resident ungulates.

This careful management principle can, and should, be extended to the marine environment. In tandem with the ecology-system-based management and their legal enforcement, we could progress towards the maintenance of a sustainable and balanced level of marine biodiversity.

Conclusion

It is a sad reflection of our time that effective stewardship and sustainable management of the oceanic resources seem to be out of our reach.  There far too many political, parochial, cultural and economic expediency ‘blockage factors’ conspiring to prevent any significant and realistic hope for productive developments in the near future.

The underlying hope is that, in time, man will realize that his children’s future depends on the adoption of a paradigm change of thinking, education and forward investment in the future (particularly alternative renewable, non-polluting energy derivation systems). It can be argued that, over a few decades, it will prove economically beneficial to do so. In socio-economic terms, the failure to take these remedial steps could prove very costly indeed.

Article Source: https://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/25603/RippleWilliam.Forestry.TrophicCascadesYellowstone.pdf?sequence=3

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About the Author 

Monty Halls Senior is the Manager - Shark and Coral Conservation (DEEP Facilitator). Monty was born in 1938 and served as a RAF Navigator and Air Traffic Control Officer for 23 years. Thereafter he had a spell with BAE in Saudi Arabia followed by work with SITA, the communications organisation serving the IATA airlines. He then set up his own home-based letting business which he operated as a sole trader for some 10 years. After selling the business, he joined the United Nations to serve in Bosnia supervising the post-war elections. After a brief spell with the Royal Navy at RNAS Yeovilton, he retired and took up an interest in his son's diving and media career. This was the catalyst to an interest in marine conservation.

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