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Tian J.-S.,Liaoning Ocean and Fisheries Science Research Institute | Tian J.-S.,CAS Qingdao Institute of Oceanology | Lu Z.-C.,Liaoning Ocean and Fisheries Science Research Institute | Lu Z.-C.,CAS Qingdao Institute of Oceanology | And 6 more authors.
Chinese Journal of Ecology | Year: 2015

This study measured δ13C and δ15N in muscle, liver, kidney, lung, hair, whisker and nail from juvenile and adult captive spotted seals Phoca largha after feeding Clupea harengus and Mallotus villosus for more than 6 months to produce the fractionation in each tissue. Meanwhile, this study estimated the food sources for the wild spotted seals from Liaodong Bay, in terms of δ13C and δ15N fractionations in muscle, liver and kidney of wild spotted seals and its potential foods in Liaodong Bay. The results showed that the highest δ13C value in captive spotted seals was in whisker (3.5‰), followed by hair (3.2‰), nail (3.0‰), muscle (1.3‰), lung (1.0‰), liver (0.5‰) and kidney (0.3‰). The highest δ15N value in captive spotted seals was in kidney (2.8‰), followed by liver (2.7‰), muscle (2.6‰), nail (2.6‰), whisker (2.6‰), lung (2.4‰) and hair (1.8‰). The δ13C values in captive pup were -22.4‰, -23.0‰ and -22.1‰ in muscle, kidney and liver, respectively. The δ13C value in milk was -24.8‰. The δ13C values in wild adult spotted seals from Liaodong Bay were -18.6‰, -19.1‰ and -18.7‰ in muscle, kidney and liver, respectively. According to the fractionation (1.3‰) of δ13C in captive spotted seal muscle, the estimated food sources for wild spotted seals from Liaodong Bay were mainly from fishes (especially pelagic and meso-demersal fishes), and some cephalopoda and shrimps as well. © 2015, Editorial Board of Chinese Journal of Ecology. All rights reserved.

Zhang P.J.,Liaoning Ocean and Fisheries Science Research Institute | Song X.R.,Dalian Sun Asia Tourism Holding Co. | Han J.B.,Liaoning Ocean and Fisheries Science Research Institute | Wang L.M.,Liaoning Ocean and Fisheries Science Research Institute | Yang Y.,Dalian Sun Asia Tourism Holding Co.
Canadian Journal of Zoology | Year: 2014

As lactation is commonly very brief in phocid seals, the transfer of sufficient energy between mother and offspring is critical for their reproductive success. In this study, we investigated variation in the pattern of energy transfer and allocation during lactation in the spotted seal (Phoca largha Pallas, 1811). Temporal changes in milk composition, milk consumption, and pup mass gain were analyzed from birth to weaning in a spotted seal pup that was hand-reared on a donor-female's milk. In addition, growth rates were measured in six pups raised in captivity but nursed naturally. We found that milk fat content increased and water content decreased during lactation. We calculated that spotted seal pup ingest a mean (±SD) daily energy of 39.5 ± 8.6 MJ/day, which corresponded to a daily mass gain of 0.9 kg/day. We found that the growth rates of the hand-reared pup and the six naturally reared pups did not differ, and overall, the mean (±SD) daily growth rate of spotted seal pups was 1.1 ± 0.2 kg/day before weaning and 0.6 ± 0.2 kg/day from birth to molt. Our study provides the first data on lactation patterns in this species.

Zhang P.,Liaoning Ocean and Fisheries Science Research Institute | Zhang P.,CAS Qingdao Institute of Oceanology | Yang Y.,Dalian Sun Asia Tourism Holding Co. | Han J.,Liaoning Ocean and Fisheries Science Research Institute | And 8 more authors.
Theriogenology | Year: 2014

Spotted seals (Phoca largha) are ice-breeding phocid found in eight different breeding colonies all over the world. They exhibit a seasonal breeding pattern, with annual and synchronous cycles; however, little is known about their reproductive endocrinology. In this study, we measured serum testosterone, progesterone, and 17β-estradiol concentrations in captive spotted seals (simple number: female n=68; male n=89) throughout a full reproductive cycle. Males that were older than 4years had significant testosterone fluctuations and were, therefore, classified as sexually mature. These animals show significant seasonal changes in testosterone levels, with average peak concentrations of 10.81±9.57nmol/L (±SD) from November to February, compared with mean concentrations of 1.42±3.09nmol/L throughout the remainder of the year. Females that reported a significant variation in progesterone concentrations and were older than 4years were considered to be sexually mature. In these females, progesterone levels increased in February, remained elevated for 7months with a mean value of 37.39±17.03nmol/L, and then dropped to 0.74±0.54nmol/L. Serum 17β-estradiol levels were also found to be significantly increased in January, remained so for 8months (15.80±14.15ng/L), and then declined after August (7.77±6.78ng/L). In seals, mating typically occurs in February and March, 1month after the observed peaks in testosterone and estradiol concentrations and corresponding to the increase in progesterone. A moderate positive correlation between testosterone and progesterone concentrations in sexually mature males was also observed (Spearman rho, r=0.63, P<0.01). In sexually immature females, progesterone and estradiol concentrations were found to be significantly lower than those in mature females. Finally, the observed patterns of estradiol and progesterone in sexually mature females suggest that embryonic diapause or successful implantation occurs in August. © 2014 Elsevier Inc.

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