Thursday, January 20, 2011

Sharks - the Science!

I must confess, I'm a big fan of Pew.
Case in point: Sharks: The State of the Science from their Ocean Science Series that represents a very good starting point when talking about Shark Conservation.

Too busy to read it all?
Here's the Executive Summary.

The biological characteristics of sharks make them particularly vulnerable to overfishing.
They grow slowly, become sexually mature relatively late and produce few offspring. This vulnerability is reflected in the large number of shark species that are considered to be threatened or endangered.

A review of the current scientific literature on the number of sharks killed per year, the causes of this mortality, the status of shark species worldwide and the impact on ecosystems after large predators are removed provides the following key points:

* Millions of sharks are killed every year to supply the fin trade. In 2000, for example, 26 million to 73 million sharks were killed for fins, corresponding to 1.21 million to 2.29 million tons of shark.

* Commercial fisheries targeting sharks occur throughout the world. Sharks are sought primarily for their fins and meat but also for their cartilage, liver and skin.

* The highest numbers of reported shark landings are from: Indonesia; India; Taiwan, Province of China; Spain; and Mexico.

* Shark bycatch is frequently reported in pelagic longline fisheries targeting tuna and swordfish and can represent as much as 25 percent of the total catch. This bycatch is considered to be a major source of mortality for many shark species worldwide.

* Blue sharks make up an especially large fraction of shark bycatch in pelagic fisheries (47–92 percent).

* The value of shark fins has increased with economic growth in Asia (specifically China), and this increased value is a major factor in the commercial exploitation of sharks worldwide.

* Declines in population sizes of sharks, as much as 70–80 percent, have been reported globally. Some populations, such as the porbeagle sharks in the northwestern Atlantic and spiny dogfish in the northeastern Atlantic, have been reduced by up to 90 percent.

* The removal of large sharks can negatively impact whole ecosystems by, for example, allowing an increase in the abundance of their prey (fewer sharks eat less prey), or influencing prey species through non-lethal means, by causing behavioral changes to prey habitat use, activity level and diet.

* Live sharks have a significant value for marine ecotourism (for example, recreational diving, shark feeding and shark watching) that is typically more sustainable and often more valuable than their individual value to fisheries. Whale shark tourism, for example, is estimated to be worth $47.5 million worldwide.

My only question mark: the percentages of decline in population numbers.
This is once again one of those numbers, once again probably an exaggeration. With all due respect for the laudable intentions, I just don't believe that it is accurate - probably not even locally and certainly not on a global scale. For that, we would have to dispose of reliable baseline counts, and we would have to be able to reliably estimate the number of Sharks that live today.

Sound plausible to you?
And if not, are we again shooting ourselves in the foot by not being strictly fact based?
How about, again, Too Many?

The section about Shark Tourism fascinates me.
Here is the back-of-the-envelope calculation for our Sharks, in Fiji Dollars. One FJD is worth fifty US cents.
  • The yearly turnover of Beqa Adventure Divers is FJD 1,100,000 (of which FJD 45,000/year marine park levy that goes to the villages), all of which gets re-invested in country. Add to that the ancillary revenues in the tourism industry (airline tickets, transfers, accommodation, meals, souvenirs, excursions etc) and assume that the ratio is 1:2 (which is very conservative!) = FJD 2,200,000, gives a total of FJD 3,300,000.

  • We work with approx 100 Sharks, meaning that every Shark contributes FJD 33,000 to the Fiji economy - not once but per year!

  • Assuming that on average, a Shark will live for 20 years (less for Whitetips, more for Bulls), then the value of one Shark on our Shark dive is FJD 660,000.

  • Our competitors work with the same Sharks. Assuming that their cash flow is similar to ours, one can double the above numbers.
Pretty darn impressive huh!

PS thank you Patric!

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