The dolphin fish, Corphaena hippurus Linnaeus, is one of the most important migratory fishes on the east coast of Taiwan. Present results are based on an investigation of 1439 specimens caught using long‐line and driftnet, and set net collected monthly between September 1996 and September 1997. The sex ratio of female to male and female combined was 65%, demonstrating a female predominance. Oocytes became mature and transparent when they attained 1.0 mm in diameter. The total number of oocytes per ovary was estimated to range from 2.78 × 105 to 23.48 × 10>5, but batch fecundity was noticeably lower than the total number of ovarian eggs, ranging 5.3–32.7% (average 30.1%), and the relative fecundity ranging 10–344/g bodyweight (mean 111/g bodyweight). Minimum body size at sexual maturity was estimated to be 51 cm for both sexes. Dolphin fish spawned throughout the year with reproductive activity peaking in February to March. It is suggested that the dolphin fish has an extended spawning season, during which it lays eggs almost continuously.

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Reproductive biology of the common ponyfish Leiognathus equulus was described based on 958 specimens caught by otter trawlers in the south-western waters off Taiwan and landed at Tungkang and Linuan fishing ports from March 2000 to February 2001. Macroscopic appearance of the ovary, gonad-somatic index, oocyte diameter frequency distribution, and histological examination suggested that the spawning season of the common ponyfish in south-western Taiwan waters is from May to August. Eight stages of oocyte development were determined based on histological examination, and ovarian development can be divided as immature, early maturing, late maturing, mature and spent stages. The sex ratio of 0.52 was not significantly different from 0.5 using c 2 test, but females were overwhelmingly more when fork length (FL) was greater than 170 mm. The relations between fecundity (F), batch fecundity (BF), and body weight (BW) were estimated to be F = -5328 + 1.2946 BW (n = 132, P < 0.05) and BF = -11.26 + 0.2748 BW (n = 25, P < 0.05), respectively. Mean fecundity and mean batch fecundity (± standard error) were estimated to be 129 955 ± 79 343 and 28 160 ± 14 698, respectively. Sizes at 50% maturity estimated from the Logistic model were 162 mm FL and 158 mm FL for females and males, respectively.KEY WORDS: common ponyfish, Leiognathus equulus, reproductive biology, south-western Taiwan.

The dramatic decline in annual yield of the Japanese butterfish, Psenopsis anomala, in southwestern Taiwan over the past decade suggests that this stock might have been overexploited. However, its fishery biology and stock status is poorly understood. This study therefore provides the first information on P. anomala reproductive biology based on 983 specimens collected by small trawlers in southwestern Taiwan waters between February 1999 and February 2000. The sex ratio, 0.44 (431 ⁄ 983), differed significantly from 0.5 and females predominated in fork length above 180 mm. The relationships between body weight (BW) and fork length (FL) were estimated as BW = 1.62 · 10 )4 · FL 2.637 (r 2 = 0.74; n = 430, P < 0.01) for females and BW = 1.28 · 10 )4 · FL 2.671 (r 2 = 0.82; n = 552, P < 0.01) for males. Oocytes were mature at 0.5 mm in diameter or larger, and transparent eggs were found at diameters of 0.85 mm. Mean fecundity was estimated at 171 900 ± 61 700 and fecundity (F) was found to increase exponentially with gonad weight (GW) F = 5.4967GW 0.511 (n = 132, r 2 = 0.74). Mean batch fecundity was estimated to be 83 400 ± 44 600, and relative fecundity from 377 to 2588 (mean 1040) per gram body weight. Logistic curves describing the relationship between proportion of maturity (Pr) at each length interval and fork length were estimated as Pr = 1 ⁄ (1 + e 11.4194)0.0749FL ) (r 2 = 0.99, n = 351) for females and Pr = 1 ⁄ (1 + e 11.5113)0.0732FL ) (r 2 = 0.99, n = 258) for males. Size at 50% maturity was estimated as 15.7 and 15.3 cm FL for females and males, respectively. A multi-spawning pattern was observed in the Japanese butterfish whereby it spawns throughout the year with a peak from February to July. A seasonal closure from April to July (spawning season for most fish species) can provide better breeding opportunities for adults and is believed to be a good fishery management measure for this species.

ABSTRACT1. In order to promote the establishment of the first marine protected area (MPA) in Taiwan, the conservation values of 12 reef sites in the Penghu Islands were evaluated. The results together with a 6-year surveillance programme revealed that the Chinwan Inner Bay (CIB) possesses the best coral community in the Penghu Islands with the highest coral cover, high species diversity and habitat types, as well as a high conservation value.2. Utilization of biological resources and socio-economic factors of CIB were investigated by intensive field surveys and a complete visit-and-poll survey respectively. Most of the fishing at CIB is for recreational purposes and is characterized by low investment, low harvest rates, high dependence on weather conditions, and self-consumption.3. The socio-economic data showed that there was basically no direct conflict of interests with local communities at two neighbouring villages, and most local residents indicated that they would support the MPA proposal. 4. A blueprint for a CIB MPA based on the results of these biological and socio-economic investigations is proposed. Environmental threats including anchor damage and the predation of Drupella snails need to be ameliorated and monitored through the implementation of appropriate management. The involvement of local communities is key to the success of this MPA and environmental education is recommended to promote public awareness.