On China's lake fisheries development

An account is given of the current situation regarding the lake fisheries and fish culture practices in China. The modern lake fisheries take advantage of the 3-D spaces of lakes to fully develop the resources. Currently, the fisheries concentrate on the following 3 aspects: bringing the water body into full play; various types of aquaculture enclosures; and selective measures in resources protection, stocking and aquaculture.

Recruitment season, size, and age of young American eels (Anguilla rostrata) entering an estuary near Beaufort, North Carolina

Net catches from 1985–86 to 1994–95 at Pivers Island, North Carolina, indicated that glass-eel stage American eels (Anguilla rostrata) were recruited to the estuary from November to early May, with peak numbers in January, February, and March. There was no declining trend in recruitment over the years of sampling. Except for one year, there was no clear seasonal decrease in mean length. But shorter glass eels were older than longer glass eels, as judged by age within the glass eel growth zone of the otolith, suggesting that smaller fish took longer to arrive. The mean age of glass eels collected from the lower estuary and a freshwater site 9.5 km upriver differed by 8.4 d (36.2 vs. 44.6, respectively). Outer increments (30–35) of the otolith growth zone of glass eels from North Carolina were significantly wider than corresponding increments of otoliths from New Brunswick. Mean total ages of North Carolina, New Jersey, and New Brunswick elvers were 175.4, 201.2, and 209.3 d, corresponding to mean lengths of 55.9, 60.9, and 58.1 mm TL, respectively. The mean durations of glass-eel growth zones (44.6, 62.3, and 69.8) were in close agreement with those from previous studies, but total ages were not. This suggested that perhaps some finer (leptocephalus stage) increments were not detected by light microscopy, differences occurred in seasonal increment deposition, or absorption of the otolith material may have taken place during metamorphosis, rendering the aging of larvae inaccurate. Judging from the long recruitment period and seasonal uniformity in both mean age and length found in our study, the spawning period of American eels may be somewhat more protracted than previously considered.

Contribution of zooplankton to the fishery of Dharamtar Creek, adjoining Bombay Harbour

The rich zooplankton standing stock of Dharamtar Creek showed a variation of 8 to 5261 (av. 1032) mg C/100 m super(3)/d which led to a turnover of 29 tonnes C/km super(2)/y. The estimated fishery potential from zooplankton production was 0.079 tonnes C/km super(2) or 29.00 tonnes/km/y. The worked out yield in terms of wet weight of fish was 0.059 tonnes/km2u2/d. Experimental trawling within the creek showed a potential of 0.19 tonnes/km super(2)/d suggesting a transfer coefficient of only 31.4% form secondary to tertiary level. Fish eggs and larvae were very common in the area but contributed collectively only 1% to the total zooplankton population. On an average the outer zone sustained relatively higher population of fish eggs and larvae than the interior zone. The mean population density of larvae (334/100 m super(3)) was 3.5 times higher than fish eggs (93/100 m super(3)) suggesting the good survival rate and a congenial environment for larvae to thrive.

Primary productivity in polluted environments of Bombay

The coastal areas of Bombay are generally turbid and the euphotic zone in these waters hardly exceeds 6 m. Primary productivity is largely confined to surface layers. Nearshore polluted stations have low values of dissolved oxygen, salinity and pH. Nutrients, on the other hand, are high. Primary productivity in these areas was 16.86 mg C m super(-3) d super(-1) in October. Column production for all the 4 stations ranged from 10.32 to 2511.30 mg C m super(-2) d super(-1). A direct correlation was found between nutrients and productivity values.