Prenatal investment directly determines the size at birth and fetus growth rate, which affects neonatal survival and growth and potentially affects maternal fitness. This study explored the associated prenatal life history traits of cetaceans. Using multivariate analysis and ANCOVA, baleen whales and toothed cetaceans had distinct energy patterns, with two exceptions including beaked whales and eusocial cetaceans. Baleen whales are characterized by fast prenatal growth, which suggests high prenatal energetics, and utilize the capital breeder tactic. Toothed cetaceans, except for beaked whales, utilize income breeder energetics, which yields relatively slow prenatal growth. However, eusocial cetaceans have especially slow prenatal growth, suggesting very low prenatal energetic effort with social compensation. Although beaked whales are behaviorally income breeders, both discriminant analysis and ANCOVA showed that they are energetically similar to baleen whales, utilizing capital energetics. ANCOVA further revealed that beaked whales have comparatively large calf size, suggesting high prenatal investment. Because all cetaceans wean their calves at comparable size, high prenatal investment may further suggest reduced cost of lactation, which may be behaviorally and energetically adaptive to their specific deep-dive-feeding niche.
Summary The cutlassfish is one of the most commercially important continental fishes in the East China Sea. However, the current classification of cutlassfishes is suboptimal and complicates fisheries management. This study investigated the growth and reproduction of three cutlassfish species in the southern East China Sea. Between August 2002 and September 2003, a total of 2717 specimens of Trichiurus japonicus, T. sp.2 (likely synonymous for T. nanhaiensis) and T. lepturus were collected monthly from Daxi, Anping, Nanfangao, Donggang and Xingang fishing ports. The von Bertalanffy growth model in preanal length (PL) resulted in PL (mm) for T. japonicus, PL(mm) for T. sp.2 and PL (mm) for T. lepturus. Their growths were significantly different between sexes for T. japonicus and T. sp.2 and among the three species. From macroscopic examination of ovaries, histological inspection of oocytes, and analyses of gonosomatic and hepatosomatic indices, T. japonicus was likely to spawn all year round, with two peaks in February–July and November–December. T. sp.2 spawned relatively later, between April and August. The length at sexual maturity of T. japonicus females was 264 mm PL or 746 mm total length. The sex ratios of T. japonicus and T. sp.2 were significantly different from 1 : 1 whereas T. lepturus showed no significant difference. The three species of trichiurids have different geographical distributions in this region.
Summary The 72 most important commercial fish species as well as nine unidentified fish groups representing hundreds of fish species as the major and minor target species caught in waters off Taiwan and the East China Sea were selected from the ‘Fisheries Yearbook Taiwan Area.’ All available published and grey literature as well as the Fish Database of Taiwan and Fishbase websites were thoroughly reviewed for a total of 108 fish species, including 51 out of 72 major and 57 minor target fish species, on their reproductive periods in waters off Taiwan and the East China Sea. The spawning periods from these commercial fish species were then summarized. An imperative adjustment was recommended for the established fishing season closure, i.e. for an earlier start, from April to June, in the southern East China Sea. This suggested correction corresponded with the spawning period of most fishes so as to maximize the protection of spawning cohorts for at least 68 major and minor target fish species, which would account for over 53% of the total fish yield in Taiwanese offshore fisheries.
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