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The knowledge of demographic traits such as longevity, growth rates and age at sexual maturity is crucial for understanding the structure of a population in its natural environment and implementing appropriate strategies for its management and conservation. Based on counts of growth layer groups in sections of decalcified teeth using the paraffin technique, we estimated the age and growth of 25 individuals of striped dolphin (Stenella coeruleoalba) found dead stranded along the coast of Campania and Calabria (south Italy, central-western Mediterranean) from 2013 to 2018. Seven individuals, with TL of 100–110 cm, were calves under 1 year old. The oldest male and female individuals were 19 and 14 years old, respectively. Growth curve estimated using the Gompertz growth model (GGM) showed that in S. coeruleoalba male growth trajectories are partly in accordance with those reported in other studies on the same species from different Mediterranean areas. The high frequency (28%) of calves strongly suggests that females of this species use the marine area all around the south-western Italian coasts to give birth to their offspring. Furthermore, a comparison with the estimated age of striped dolphins from other Mediterranean marine areas shows that the longevity of the individuals examined in this study is much lower. Our study provides information toward understanding the demographic traits of S. coeruleoalba from Mediterranean Sea. The results reported here can be useful for future research aimed at understanding population structure, mortality patterns and the effects of anthropogenic activity on the survival of this species in this marine area.

Results of the examination of 1 062 sei whales Balaenoptera borealis landed at the whaling station at Donkergat, Saldanha Bay, South Africa, in the 1962 and 1963 whaling seasons are presented. Sei whales were usually encountered off the edge of the continental shelf, with males being caught closer inshore than females and mature females furthest of all from the station. Females reached puberty at an average length of 46.1 ft (14.1 m) and an age of 8.2 (95% CI = 7.3, 9.0) years (assuming one growth layer group is formed in the ear plug per year). Males reached sexual maturity at an average length of 45.3 ft (13.8 m) and an age of 8.6 (95% CI = 7.8, 9.4) years. Mean lengths at which growth ceased were 52 ft (15.8 m) in females and 48.6 ft (14.8 m) in males. Most (~90%) conceptions occurred over a 70-day period with a peak in June, and primigravid females conceived six days later than multigravid females. Observed pregnancy rates were as high as 86.1%, but with ovulation rates averaging only 0.47 a year, the catch could not have been fully representative of the population. There was no significant decline in the observed pregnancy rate with age. During the northward migration (May–July), fewer whales were taken in water shallower than 2 000 m than in the southern migration, and the catch was largely composed of immatures. The few adult males taken at that time of year had significantly heavier testes than males of an equivalent size on the southern migration. The southward migration (August–October) was markedly structured, such that pregnant females and immatures of both sexes were in the vanguard, followed by mature males and lastly lactating females and calves. The availability of sei whales off Donkergat declined rapidly from 1965 to 1967, following an episode of massive catching by pelagic whalers in higher latitudes. Keywords: growth, migration, reproduction, sei whales, South Africa African Journal of Marine Science 2002, 24: 111–133

Tissues from fin (Balaenoptera physalus) and sei (Balaenoptera borealis) whales taken off the coast of Southwest Iceland in July–August in 1978 and 1981 were analysed for percent lipid, protein, and ash contents. The tail region of the whales, especially the dorsal area, constituted the main area of lipid storage in both blubber and muscle. No significant differences (p > 0.05, ANOVA) were evident between reproductive classes, except that adult females appear to store more lipid in the tail muscles than other classes. Most sei whale tissues contained more lipid than those of fin whales, but the differences may be explained by variations in seasonal feeding and fattening. Seasonal variations and differences between reproductive classes were evident from girth and blubber thickness. Juvenile males were thinnest and adult females were thickest.

Fin whale blubber is a heterogenous tissue containing 8.9–77.4% lipid, 3.1–33.8% protein, and 0.07–0.73% ash by wet weight. The blubber may be subdivided into three macroscopically distinct zones. The outermost zones contain up to twice the lipid content of the innermost zone adjacent to the muscle, which contains more protein. Anterior ventral blubber contains less lipid, more protein (of which 50% is collagen), and more ash than posterior dorsal blubber. Foetal blubber contains 1.2% lipid, 10.6% protein, and 0.93% ash by wet weight. Blubber lipid contains ca. 60% triacylglycerol and ca. 25–30% free fatty acid, compared with ca. 25% triacylglycerol and ca. 10% free fatty acid in foetal blubber lipid, which also contains ca. 40% phospholipid. The high free fatty acid component is certainly partly due to postmortem hydrolysis in samples analysed. Monounsaturated fatty acids comprise ca. 60% of blubber lipid; 16:0, 16:1, 18:1, 20:1, 22:1, and 22:6 predominate, similar to the dietary intake. The predominant fatty acids in the outermost and the innermost blubber zones are 22:1 and 16:0, respectively. This may have significance in energy storage and catabolic breakdown.