Che-Tsung Chen

The whale shark, Rhincodon typus, is a livebearer : 300 embryos found in one 'megamamma' supreme

Shoou-Jeng Joung’, Che-Tsung Chen’, Eugenie Clark’, Senzo Uchida3 & William Y.P. Huang4 I Department of Fishery Science, National Taiwan Ocean University, 2 Pei-Ning Road, Keelung 20224, Taiwan, Republic of China ’ Department of Zoology, University of Maryland, College Park, MD 20742, U.S.A. .’ Okinawa Expo Aquarium, Motobu-Cho, Okinawa Prefecture, Japan 4 R.O.C. Game Fish Association, Taipei, Taiwan, Republic of China

Age, Growth, and Reproduction of the Pelagic Thresher Shark, Alopias pelagicus in the Northwestern Pacific

Age, growth, and reproduction of Alopias pelagicus are described based on 831 specimens (508 females and 323 males) collected from September 1993 to August 1995 in waters off northeastern Taiwan. Alopias pelagicus embryos are oophagous. Five developmental stages (two encapsulated and three posthatching) are recognized. The number of embryos per litter is two, and size at birth is between 158 cm and 190 cm total length (TL). The sex ratio of embryos is 1:1. Total length at maturity is 282-292 cm for females and 267276 cm for males, which corresponds to age of 8.0-9.2 yr and 7.0-8.0 yr, respectively. Gestation period could not be determined from present data because females were in various stages of pregnancy throughout the year. Based on marginal increment analysis and verified by length-frequency analysis, annuli in precaudal vertebrae form once a year and numbered up to 16 and 14 for females and males, respectively. However, extrapolating the growth rates for the largest sharks would yield maximum ages of 28.5 yr and 17.5 yr for females and males, respectively. The von Bertalanffy growth equations in PCL were estimated as Lt = 197.2(1 e-0.085(t+7.67)) for females, and L, = 182.2(1 e-0118(t+5.48)) for males.

Reproduction in the Sandbar Shark, Carcharhinus plumbeus, in the Waters off Northeastern Taiwan

The purpose of this study was to investigate the reproductive biology of sandbar sharks, Carcharhinus plumbeus from northeastern Taiwan waters. A total of 885 sandbar sharks was examined. The size of 50% maturity in sandbar shark is taken to be 170-175 cm and 175 cm for females and males, respectively. The number of embryos per litter ranged from four to 12, with a mean of 7.54. Pregnant individuals containing six, seven, or eight embryos constituted 59 (80%) of the 74 females examined. Of 558 embryos in 74 litters examined, 274 were female and 284 were male. The null hypothesis of a 1:1 sex ratio is not rejected at the 0.05 level. Pups are born from Feb. to April. We estimate the gestation period to be 10-12 months. Most embryos had attained a total length of about 60-65 cm after 10-12 months of development, at which size they could be readily separated from the placenta, suggesting that they were full term and ready to be born. The relationship between the total number of uterine embryos and the total length of mother is roughly described by the regression equation (n = -7.544 + 0.075 TL; n = 74; r = 0.41). Although it is clear from this regression that fecundity is related to the size of the mother, the relationship is not particularly strong. We find that fertilization occurs during April and May, two months prior to the estimate reported by Taniuchi for C. plumbeus in Japanese waters.

Reproductive biology of the bigeye thresher shark,Alopias superciliosus (Lowe, 1839) (Chondrichthyes: Alopiidae), in the northwestern Pacific

Reproductive aspects ofAlopias superciliosus in the northwestern Pacific were described in detail, on the basis of 629 specimens (429 females and 200 males) collected from January 1984 to October 1984 and from October 1992 to March 1994.Alopias superciliosus embryos are oophagous. Six developmental stages (3 encapsulative and 3 posthatching) based on embryonic morphology and source of nutrition were recognized. The species bears 2 embryos per litter, their size at birth being between 135 and 140 cm TL. The sex ratio of embryos was 1∶1. Total length of females at maturity was 332–341. 1. cm; of males 270.1–287.6 cm. The gestation period could not be determined because most adult females were pregnant throughout the year. The typical reproductive strategy ofA. superciliosus is the production of a few large embryos per litter, with no fixed mating or birthing season.

Reproduction of the blacktip sawtail catshark,Galeus sauteri, in the waters off northeastern Taiwan

The reproductive biology of blacktip sawtail catsharks,Galeus sauteri, in northeastern Taiwan waters was investigated. Male catsharks possessed paired testes producing spermatozoa, which were then stored in the epididymides all year round. No spermatophores were observed in the lower ductus deferens. Only the right ovary was functional in females, oogonia being formed in the ovarian cortex and then developing into mature ova. Ova exceeding 17 mm in diameter were ovulated. Pregnant individuals contained one eggcase only, in each side of the uterus. No hatched embryos were observed in such eggcases. The size at which 50% of blacktip sawtail catshark specimens were mature was 410–420 mm and 350–360 mm for females and males, respectively. The species does not have a well-defined reproductive season.

Reproductive biology of Japanese butterfish Psenopsis anomala (Stromateidae) from coastal waters of northeastern Taiwan

Abstract The reproductive biology of Psenopsis anomala was examined from semimonthly trawl samples collected in northeastern Taiwan. Male P. anomala matured at 157 mm fork length (FL) and females were mature at 168 mm FL. Sex ratio of P. anomala was skewed toward females during the spawning season but was dominated by males in non-spawning seasons. Females also dominated the large size classes. The spawning season of P. anomala began in March and lasted for about 6 months (to August). P. anomala decreased in body condition before and during spawning, then increased in condition after spawning, and reached peak condition in early winter (December). The hepatosomatic index increased during late winter (February), peaked in May prior to peak spawning in June–August and decreased to its lowest value immediately after spawning. The patterns indicate that P. anomala reduced feeding activity and used reserved energy in muscle and liver for spawning. The fecundity of P. anomala ranged from 43 to 155 thousand eggs, with a mean of 80 thousand eggs. Batch fecundity ranged from 25 to 62 thousand eggs, which is 31–46% of total fecundity. P. anomala in northeastern Taiwan matured at a smaller size, were more fecund and exhibited an earlier and more protracted spawning season than those found off Japan and in the East China Sea. Geographical variations in reproductive biology suggest that P. anomala is able to adjust phenotypic response to environmental conditions that vary with latitude.

Population structure of yellowfin seabream,acanthopagrus latus, from the waters surrounding taiwan, based on mtDNA sequences

A canthopagrus latus (Houtmyn, 1782) is one of the most valued seabreams in the Acanthopagrus schlegeli species complex, being distributed off southern Japan, southeastern China, Taiwan, southeastern Asia and Australia, and in the Indian Ocean to southeastern Africa (Hayashi, 1993). Around Taiwan, the species has a restricted distribution, from Ilan Bay in the northeast, northward to Tanshui, and southward including the entire sand-muddy-bottom west coast, with a small population present at Tawu on the southeast coast, it is common off the northwest coast of Taiwan, but it is rare off the Penghu Archipelago in the Taiwan Strait and around the remote Matsu Island, off the mainland Chinese coast. It is a popular food fish and a major object for recreational angling in the estuarine and coastal waters :of Taiwan, as welt as being farmed in ponds by the aquaculture industry in Taiwan. Because wild stocks of seabream have declined substantially in recent years, owing to overexploitation, pollution and illegal fishing practices, there is an urgent need to resurrect them through processes of conservation, management, and mariculture. Knowledge of the population structure is a basic prerequisite for rational exploitation and management, and also for correct interpretation of ecological investigations (Ferguson and Mason, 1981). Genetic discrimination of stocks with genetic markers is an essential procedure for planing of any marine fishery resource. Before undertaking any conservation policy, it is necessary to determine the profile of genetic characteristics of natural populations and to understand the extent of genetic variation between them and pondcultivated stocks of Acanthopagrus tatus, by mtDNA sequencing or some other molecular approach. However, mtDNA analysis, which reveals rapid rates of evolution, is more likely to show differences between populations, and is recognized as a good approach for population genetic studies (Ferris and Bergs, !987; Park and Moran, t995). The present study focused on the noncoding region located mainly between the tRNA e~~ and tRNA ~h~ genes with an extension of 48bp at the 12S rRNA gene. This region has a supposedly rapid rate of evolution (Hoetzel et al., 1994)

The Occurrence of Two Lanternsharks of the Genus Etmopterus (Squalidae) in Taiwan

Two forms of the lanternshark,Etmopterus, reported from Taiwan waters under the nameEtmopterus lucifer were reexamined.E. lucifer sensu Teng (1959), Chen (1963) and Shen and Ting (1972) does not conform to the original description ofE. lucifer Jordan et Snyder, 1902. One form described by Shen and Ting (1972) conformsto E. splendidus Yano, 1988, whereas another form reported by Teng (1959) and Chen (1963) agrees well withE. molleri (Whitley, 1939). These were identified based on a combination of the following characters: shape and length of the flank and caudal markings, position of the posterior end of flank markings, shape of the upper teeth, distributional patterns of dermal denticles on the second dorsal fin and preoral area, and length of the caudal peduncle.