black sea red data book - Department of Biology

movements between the Black Sea and Mediterranean populations seem possible, but
no direct evidence for this has been obtained. Critical habitats are not so clear as
dangerous zones (e.g. Black Sea straits and forestrait areas), where animals may get
hurt by heavy marine traffic, fisheries and pollution. Two natural pathogens are
known to cause mass mortality: the lung nematode Skrjabinalius cryptocephalus and
an unidentified morbillivirus. The morbilliviral disease observed in July-September
1994 was accompanied by the stranding of sick animals.
Biology. Black Sea individuals seem to be the smallest representatives of this species
anywhere in the world: the average length is 1.5-1.7 m (maximum 2.0 m) for adult
females, and 1.7-1.8 m (maximum 2.2 m) for males. According to dental growth
layers, females and males attain sexual maturity after 2-4 and 3-4 years; life span is
20-22 years or more (probably 25-30 years). The mating period (ate spring-early
autumn) peaks in July-August. The annual pregnancy rate of the population (46-75%
of fertilized females) depends on the duration of calving intervals, estimated at 1.3 to
2.3 years. Gestation (one foetus) and lactation take up 10-11 and 14-19 months, but
calves feed on the mother's milk only for the first 5-6 months. Small pelagic fishes,
forming large aggregations (sprat, anchovy, pipefish), are the basic prey of subadult
and adult animals (daily ration 4-10 kg).
Population trends. The Common dolphin population still continues to be the most
abundant cetacean in the Black Sea despite over-exploitation (mass kills on an
industrial basis) during 1930s-early 1980s. However, this point of view is not more
than a speculation, not based on of reliable scientific data. The stock of Common
dolphins in Romanian waters is estimated at 600-800 individuals.
Threats. Contemporary human activities limiting the Black Sea population have not
been adequately studied. By-catches in bottom-set gill nets are not frequent, and
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