Study on fish life history traits and variation in the Taiwan Strait and its adjacent waters

Large portions of the world＇s fishery resources are overexploited. Life history traits of fish species are important indicators to reveal different life history strategies and to indicate population responses to fishing pressures. For this study, empirical data on fishing grounds located in the coastal area between Fujian Coast and Taiwan Island were collected. These areas have experienced severe overfishing in the past 30 years, leading to changes in the structure and function of the fish communities. Fifty-one commercial fish species in this fishing ground were selected to study the life history traits. Using the life history traits, all the species were grouped into five different life history strategies by principle component analysis. More than 60% of the species were categorized in Group 5 that was similar to r-strategists. Twenty-five commercial species were selected for further analysis of changes in life history variables, and to discuss the population responses to exploitation. Results showed that most of the species appeared to become smaller size, shorter life, earlier maturation and faster growing under long-term exploitation. The exploitation rate of each species was also calculated to further discuss the impacts of fishing pressures to fish populations. Four species were found with the severest changes on life history traits indicating some of the species might be more susceptible to exploitation. This study on fish life history traits and their long-term variations under fishing pressures could provide important scientific implications for fishery management and conservation.

Calculation of current in the Taiwan Strait during summerⅡ. Three-dimensional semidiagnostic and prognostic calculations

The semidiagnostic and prognostic models are used to compute the current in the Taiwan Strait with wind and hydrographic data collected during August, 1984 and September 1 ~ 6, 1988. This calculation can be divided into two stages, i. e. (1 ) the adjustable stage; (2) prognostic calculation. The computed result shows tha the density and velocity fields etc. have been adjusted when t = 2. 5 d, namely the solution of semidignostic calculation is obtained,and the quasi-steady state solution have been reached after about 40 d. Comparing the results of diagncotic calculation with those of semidiagnortic and prognostic calculations indicates that they agree qualitatively. For example, they all have the following common features: (1 ) there is a persistent northward fiow with a volume transport of 0. 8 × 10 6 m3/s through the Taiwan Strait in summer; (2 ) the current near the western coas of Taiwan is stronger than that in other regiona; (3) the upweiling occurs near the Fujian coast and so on. However, there is a quantitative difference between them as follows. For example, the horizotal velocity near the westem cot of Taiwan and the upwelling speed near the Fujian aret both are underestimaed in the diagnestic calculation, because the data used in which is smoothed, and they both are intensified in the solutions of semidiagnostic and prognostic calculations. For example, the maximum velocity near the western coast of Taiwan at t = 0 d (diagnostic), 2. 5 d (semidiagnostic) and 300 d (prognostic) is 59.1, 62. 1 and 62. 0 cm/s, respectively. From the above comparison we see it is quite necessary that a semidiagnostic model be used to compute the currents when the data have been smoothed.

Primary production processes in the Taiwan Strait──Spatial and temporal variations of phytoplankton biomass and productivity

The abundance,diurnal variation features of phytoplankton biomass and the horizontal distribution patterns of Chl. a and primary productivity in the Taiwan Strait were investigated during a summer and a winter cruise inAugust 1994 and February 1995, respectively. Results show that the horizontal distribution of phytoplankton biomasswas quite similar to that of productivity.In summer, there was a relatively barren, low priductive region in the centallocation of the northern Taiwan Starit (NTS), and high productive regions were located at the nearshore and to thenorth of Cape Fugui of Taiwan Island; meanwhile, high productivity regions were only located at coastal waters of thesouthern Taiwan Strait (STS). In winter, high productive regions of NTS occurred off northwestern coast of TaiwanIsland, while that of STS was located along the southem edge of Minnan (South Fujian) - Taiwan Bank. Vertical patterns of the diurnal variation of Chl. a indicated that in non-stratified waters, phytoplankton biomass changed in tiedrhythm; as for the stratified waters, the depth at which the highest variation amplitude located located coincided with thedepth where the highest variation frequency occurred. The grazing pressure of zooplankton strongly influenced the diurnal variation of size-fractionated structure of phytoplankton biomass. As a result of our investgitions, we concludethat in the Taiwan Strait, biological porcesses may be more important at smaller scales where behaviors such as verticalmigration and predation may control the phytoplankton production, whereas physical processes may be more importantat larger scales in structuring phytoplankton patchness.

Dynamics of DOC of euphotic layer in the Taiwan Strait─—Diurnal variation of large range

Three oceanographic investigations from 1994 to 1995 in the Taiwan Strait show that the dissolved organic carbon (DOC) in the euphotic layer has a large-scale diurnal variation [2 ~ 4 mg/dm3], and its amplitude range has spatial and seasonal changes. Generally, the DOC in the euphotic layer is higher at day than that at night. According to the diurnal variations, DOC can be divided into two parts: new DOC and old DOC. The content of new DOC varies rapidly every day but the content of old DOC does not. Though there is still not a good explanation for this diurnal variation of DOC, it may call attention to the study of organic carbon dynamics, especially the DOC primary production of phytoplankton, the DOC utilization of bacteria, and the flux of DOC in coastal sea water.

Test of numerical prediction of sea water temperature in the Taiwan Strait

A dynamic numerical prediction model of sea water temperature for limited sea area is used to predict the sea water temperature at the sea area near Fujian. Essential adjustments have been made in accordance with the characteristics of this region. Two Tests have been made. One is in summer (3 d) and the other is in winter (10 d). In the summer test, a typhoon is just passing by and the calculated current field well responds to typhoon. In the winter test, variation tendency of the predicted sea water temperature field agrees with that of the observation basically, the absolute mean error in the whole sea area is 0 .6 ℃. The variation of the sea water temperature is mostly af- fected by entrainment and pumping, which is related to the topography of the strait.

Species composition and distribution of marine nematode community in the North Taiwan Strait

Marine free-living nematodes were investigated at 13 sampling stations divided into three transects in the northern Taiwan Strait in February 1998. One hundred species of marine nematodes belonging to 91 Genera 28 Families 3 Orders were identified and were first recorded in the northern Taiwan Strait. The dominant species were Vasostoma sp., Sabatieria sp. 1, Linhystera sp. 1, Spilophorella sp., Daptonema sp., Halalaimus sp. and Dorylaimopsis variabilis. Their main densities were all over 4 950 ind./m2. According to mean density at transects, marine nematode density decreased from coastal Weitou to off Minjiang Estuary, which was similar to polychaete distribution in northern Taiwan Strait. The selective deposit feeder (1A) was the dominant food type of marine nematodes in the northern Taiwan Strait, but non-selective deposit feeders (1B) and epigrowth feeders (2A) occupied high proportion, indicating diverse feeding types of marine nematodes in the northern Taiwan Strait. Some environmental factors such as currents are discussed.

Chemical characteristics and estimation on the vertical flux of N，P，Si in upwelling area of Taiwan Strait

Based on the data obtained from oceanographic surveys at the central and northern parts of the TaiwanStrait during the period from 1983 to 1988, it is showed that the nutrient content in the coastal and bottom waters isrelatively high with an upward and offward decrease, and that the upwelling in the Fujian coastal area controls the distribution of nutrients in summer.The upwelling water is characterized by 2. 29 μmol/dm￣3 of nitrate; 2. 83 μmol/dm￣3of silicate; 0. 20 μmol/dm￣3 of dissolved inorganic phosphate,respectively. Significant correlation between nutrientsand dissolved oxygen content and its degree of saturation, temperature, and salinity, respectively are found in the upweiling area. Average of N/P ratio in the area(15. 9) approaches to Redfield ratio. Their vertical flux is estimated tobe 23. 6 mg/(m￣2·d) for - P, 223 mg/(m￣2·d) for NO-N, 302 mg/(m￣2·d) for SiO-Si, respectively,which is the main source Of nutients in the areas in summer. The mean of the flux of P and NO-N is about86 % and 73% necessary for phytoplankton in the euphotic zone.

Characteristics of metals in atmosphere over the western Taiwan Strait─Ⅰ. Concentrations and distributions

One hundred and eighty-one aerosol samples, and two cascade impector samples were collected in the atmosphere over the western Taiwan Strait from 1991 to 1993. Concentrations of Al, Fe, Cu, Pb, Cd and Na were determined by an atomic absorption spectrophotometry. The contents of Fe, Cu, Pb and Cd in the atmosphere over thewestern Taiwan Strait were lower than those over inland cities in China, Europe or North America . Annual and seaed variations of concentrations of the metals could be primarily attributed to washout or monsoon for non-sea-saltmetals. Fe was presented in bimodel distributions with size around 3. 6 and o. 52 μp, As was chieny distributed on theparticles with being greater than 2. 1 μm, Na on the particles with being greater or equal to 3. 6 μp, and the size distributions of Cu, Pb and Cd were presented in small particles, chiefly on those with being smaller than or equal to0.52 μp.

Mazu Culture Links the Two Sides of the Taiwan Straits

THE goddess Mazu has been held in great esteem by emperors since the Song Dynasty (960-1279). Wherever the Chinese live, in Asia, Africa, South America and North America, there are worshipers of Mazu. According to statistics, there are more than 1,500 Mazu temples and more than 200 million Mazu devotees in the world. Mazu culture, with its unique style, affects people and promotes friendly relations of compatriots on both sides of the Taiwan Straits.