• Counter :
  • 2594
  • Date :
  • 6/9/2011

Caspian Seal

part 3

seal

The seal population faces a number of threats which, briefly, can be summarized as follows:

—Habitat degradation due to marine and boat traffic, various forms of coastal development, disruption of the food chain, impact of invasive species such as Mnemiopsis leidyi (a comb jellyfish), and destruction of breeding areas by ice-breaking ships, not to mention the possibility of the shrinking of the ice-cover owing to climatic factors;

 

—Pollution due to the oil industries, DDT, PCBs and other organochlorine pollutants;

 

—Natural mortality as a result of predation (as mentioned above), but also due to diseases such as Canine

Distemper Virus, and by the agency of humans, such as legal and illegal hunting, as well as deliberate and accidental killing of seals.

The magnitude of the threats listed above has not been studied in sufficient depth, but it is generally agreed that they all appear to be slight when compared to mortality from the harvesting of the pups for their fur and the deliberate killing of adult seals. The seal population of the Caspian has been exploited commercially for over a century. Tens of thousands were harvested each year and “for some years in the mid-20th century the numbers were in the 100s of thousands” (CISS). Clearly, the exploitation of the Caspian seal—indeed, of any species—should be sustainable. In fact, this principle is enshrined in Article 14 of the 2003 Tehran Convention, to which all Caspian littoral states are signatories.

No transparent data with regard to the pup production of the Caspian Seal population has been provided by any of the five littoral states, hence the Caspian International Seal Survey team, together with the Kazakh Fisheries Research and Production Centre (FRPC), initiated a systematic survey of the breeding seals in the frozen northern parts of the Caspian Sea. CISS used the same methods and the same international team for the Caspian survey, which had been previously used and widely accepted, to investigate the status of the ice-breeding seals in the Baltic Sea in the 1990s and early 2000s.

On the basis of this survey, estimates for the annual Caspian seal pup production were 21,063 in 2005 and 16,905 in 2006. Analysis of the data for 2007 has not been completed, but preliminary figures suggest a significantly lower number than in the previous two years. The total population of Caspian seals in 2005 was calculated on the basis of the above estimate, and an assumption of 50 percent adult female fertility, resulting in about 111,000 seals.

A statistical model based on the figure for both pup production in 2005 and hunting records (CISS states that “until the mid-1960s, both adults and pups were killed”), was used to “hind-cast” the past female population trend.

 This resulted in a total population of about 250,000 female seals in 1960, and shows a decline of more than 80 percent up to the present. CISS’s conclusion that these figures qualify the Caspian seal for inclusion in the “endangered” category of IUCN’s red list is hence justified. There is, moreover, no doubt that this decline is almost entirely due the over-harvesting of the seal population.

The Russian research institute in Astrakhan (KaspNIRKh—Caspian Research Fisheries Institute) states that according to their estimates, the population is in excess of 350,000 seals. They claim that the figures produced by CISS are based on inferior and inappropriate methodology and are hence wrong. KaspNIRKh has not, however, provided any field data or methodology to show how their estimate was arrived at or calculated. Evidently, it will be up to the CEP and/or the Bioresources Commission to enlist the best specialists available in order to resolve this unfortunate conflict on a strictly scientific basis.

Source: encyclopedia.thefreedictionary.com


Other Links:

Geography and Nature of Iran

Persian Eagles: Part 1

Persian Eagles: part 2

  • Print

    Send to a friend

    Comment (0)