The spawning patterns of two penaeid prawns, Metapenaeus endeavouri (Schmitt) and M. ensis (De Haan), were examined from data collected at 45 stations between March 1986 and March 1992. An index of population fecundity
based on the abundance, proportion and fecundity of sexually mature females was used as a measure of spawning output of the
prawn stock. The population fecundity index for M. ensis was higher than that for M. endeavouri. The monthly population fecundity index for M. endeavouri varied markedly among years, while that for M. ensis was consistent among years. Spawning of M. endeavouri occurred year-round, while that of M. ensis was concentrated mainly in spring (September to November). For M. endeavouri, a minor spawning, derived from a relatively small number of summer spawners, occurred in the 20 to 30 m offshore waters
in summer. In early summer (after May), the major spawning group consisted of large females from the winter-spawning cohort,
and the spawning area shifted to depths of 30 to 60 m. In winter (July), the major spawning, derived from the winter-spawning
cohort, occurred at depths of 20 to 40 m. For M. ensis, the major spawning, derived from the spring-spawning cohort, was observed in depths <50 m and was concentrated particularly
in inshore waters (<20 m) in spring. In autumn, the spawning output was mainly from the autumn-spawning cohort, which comprised
but a small number of individuals. In winter, the major spawning group again consisted of the large females from the spring-spawning
cohort, and spawning increased in the oceanic waters (>50 m). These results suggest that mature female M. endeavouri and M. ensis move offshore (>40 m) by May and July, respectively, and return to shallow waters (<35 m) in July and November, respectively.
The monthly reproduction patterns of both species in the “effective spawning” area showed that the major spawning season for
M. endeavouri is August to October and that for M. ensis is September to December.
Received: 19 February 1999 / Accepted: 18 June 2000 相似文献
A total of 47 passive air samples and 25 soil samples were collected to study the temporal trend, distribution, and air–soil exchange of polychlorinated naphthalenes (PCNs) in Shanghai, China. Atmospheric PCNs ranged from 3.44 to 44.1 pg/m3 (average of 21.9 pg/m3) in summer and 13.6 to 153 pg/m3 (average of 40.0 pg/m3) in winter. In the soil samples, PCN concentrations were 54.7–1382 pg/g dry weight (average of 319 pg/g). Tri-CNs and tetra-CNs were two dominant homolog groups in air samples, while di-CNs were also found at comparable proportions to tri-CNs and tetra-CNs in soil samples. Most air and soil samples from the industrial and urban areas showed higher PCN concentrations than those from suburban areas. However, some soil samples in urban centers presented higher PCN concentrations than industrial areas. Analysis of PCN sources indicated that both industrial thermal process and historical usage of commercial PCN mixtures contributed to the PCN burden in most areas. The fugacity fraction results indicated a strong tendency of volatilization for lighter PCNs (tri- to hexa-CNs) in both seasons, and air–soil deposition for octa-CNs. Moreover, air–soil exchange fluxes indicate that soil was an important source of atmospheric PCNs in some areas. The results of this study provide information for use in the evaluation of the potential impact and human health risk of PCNs around the study areas.