我国抗风浪网箱现状及发展对策

近年来,我国海水网箱养鱼发展迅速,网箱数量成倍增长。通过几年的调查研究,对目前我国抗风浪网箱养鱼的现状做了分析,指出了存在的一些主要问题,并提出了今后我国抗风浪网箱的发展方向和应采取的措施,旨在为有关部门制定产业政策和发展规划提供参考。     

高原水库目笋白鲑网箱养殖试验探讨

本文首次报道了在我国高原地区目笋白鲑水库网箱养殖试验情况。经过537d和496d网箱养殖，两批目笋白鲑平均规格分别达到441．2g／尾和280．8g／尾。该试验对我国开展白鲑鱼网箱养殖示范推广具有一定借鉴意义。     

Separation of pair housed roosters is associated with transient increased corticosteroid excretion

Immunoreactive corticosterone and corticosterone metabolites (ICCM) were quantified in excreta of permanently single housed (n = 10) and permanently pair housed (n = 20) roosters. The pair housed roosters were separated and single housed, and ICCM were quantified in the droppings before and during 15 days after separation. There was no statistically significant difference in ICCM excretion in the droppings between the permanently single or pair housed roosters. After separation, however, the previously pair housed roosters showed a significantly transient elevated excretion of ICCM in droppings the second day after separation indicating that the separation and relocation is associated with an activation of the hypothalamic-pituitary-adrenal axis.The excretion of ICCM in droppings was not correlated to the concentration of ICCM in droppings. It is thus important that excretion of ICCM be expressed as amount excreted per time unit since the total excretion is dependant on both concentration of ICCM and amount of droppings produced.     

Effect of Using Low-Protein Diets in Semi-Intensive Pond Cage Culture of Tilapia,Tilapia rendalli (Boulenger)

ABSTRACT

An experiment was carried out to determine the effect of using low-protein diets on production of Tilapia rendalli in semi-intensive pond cage culture. This was carried out at Bunda College of Agriculture's fish farm, University of Malawi, where two 200-m² earthen ponds of 1-m depth were used for two months from February 2003 to early April 2003. Each pond had 6 cages of 1 m³ in size stocked with 15 fish, each 4.8 ± 1.2 g average weight and 6.7 ± 0.6 cm average length. Chicken manure was used as the organic manure applied at 500 kg/ha/wk and also acted as a control. All treatments were replicated three times. It was observed that fish growth was higher in the soybean meal-based diet, with final weight of 34.4 g, followed by sunflower cake, with final weight of 23.3 g. The lowest was 14.4 g in the chicken manure only, and cottonseed-based diet had final weight of 19.5 g. These results also agree with the specific growth rate (SGR) that ranged from 2.1%/day in the cages only fertilized with chicken manure to 3.6%/day in the soybean-based dietary treatment. The lowest feed conversion ratio of 1.2 was also observed in the soybean-based dietary treatment. This suggests that the use of lower protein diets that contain soybean would produce better results and may increase yield when combined with fertilization, as evidenced by high fish survival rates of more than 93% in all treatments.     

Drag force acting on biofouled net panels

Measurements were made to assess the increase in drag on aquaculture cage netting due to biofouling. Drag force was obtained by towing net panels, perpendicular to the incident flow, in experiments conducted in a tow tank and in the field. The net panels were fabricated from netting stretched within a 1 m² pipe frame. They were towed at various speeds, and drag force was measured using a bridle-pulley arrangement terminating in a load cell. The frame without netting was also drag tested so that net-only results could be obtained by subtracting out the frame contribution. Measurements of drag force and velocity were processed to yield drag coefficients.

Clean nets were drag tested in the University of New Hampshire (UNH) 36.5 m long tow tank. Nets were then exposed to biofouling during the summer of 2004 at the UNH open ocean aquaculture demonstration site 1.6 km south of the Isles of Shoals, New Hampshire, U.S.A. Nine net panels were recovered on 6 October 2004 and immediately drag tested at sea to minimize disturbing the fouling communities. The majority of the growth was skeleton shrimp (Caprella sp.) with some colonial hydroids (Tubularia sp.), blue mussels (Mytilus edulus) and rock borer clams (Hiatella actica). Since the deployment depth was 15 m (commensurate with submerged cages at the site), no algae were present. The net panels had been subject to several different antifouling treatments, so the extent of growth varied amongst the panels. Drag force measurements were made using a bridle-pulley-load cell configuration similar to that employed in the tow tank. Fixtures and instruments were mounted on an unpowered catamaran that was towed alongside a workboat. Thus, the catamaran served as the “carriage” for field measurements.

Increases in net-only drag coefficient varied from 6 to 240% of the clean net values. The maximum biofouled net drag coefficient was 0.599 based on net outline area. Biofouled drag coefficients generally increased with solidity (projected area of blockage divided by outline area) and volume of growth. There was, however, considerable scatter attributed in part to different mixes of species present.     

不同笼具饲养树鼩繁殖效果研究

[目的]探讨不同笼具对树鼩繁殖效果的影响。[方法]在室内笼养条件下,将120只健康成年树鼩按1∶2雄雌比例,随机分成4组,配对饲养于A、B、C、D 4种笼具,进行为期一年的繁殖效果观察。[结果]笼具A,受孕46次,产仔136只,死产2窝,流产1窝,未出现外伤、死亡。笼具B,受孕42次,产仔126只,死产2窝,流产2窝,未出现外伤、死亡。笼具C,受孕21次,产仔68只,死产1窝,流产1窝,出现1外伤,未出现死亡。笼具D,受孕7次,产仔16只,死产1窝,流产1窝,出现2只外伤。[结论]笼具A、B适合作为繁殖笼;笼具C、D可作为一般饲养笼。     

Adding value to live, commercial size soft-shell clams (Mya arenaria L.) in Maine, USA: results from repeated, small-scale, field impoundment trials

The soft-shell clam (Mya arenaria L.) fishery in the state of Maine, USA, is worth $5–10 million annually and is primarily based on the sale of live individuals. More than 80% of the catch is sold for the “steamer clam” market that is highly seasonal due to supply and demand. Prices paid to harvesters for live clams throughout the year increases by as much as 70% during a 4-month period between early spring and late summer. If clams harvested in the spring could be held until late summer, a value-added product could be developed in this fishery. From April to August 1996, at an intertidal and subtidal location in eastern Maine, I tested whether it was biologically feasible to impound commercially harvested clams (shell LENGTH=44–75 mm) at densities between 720 and 850/m² using cages and nets (1.12 m²) to protect animals from predators. Survival was 91.7% (n=12) and 91.6% (n=6) at the intertidal and subtidal site, respectively. There was no discernible shell growth during this period and there was no difference between initial and final clam weights. The methodology was transferred to commercial harvesters in two Maine communities: Wiscasset (1997 and 1998) and Perry (2000). Impounded clams ( =21.8 kg/cage; n=18) lost, on average, 5 kg/cage in 1997 and 1998, whereas no significant net loss in wet weight occurred in cages deployed in 2000 ( =23.2 kg/cage; n=3). Differing harvesting and handling methods of individual clammers, prior to impounding clams, likely explains the variation in weight lost during the impounding periods. The difference in price per live kilogram between the beginning of the impounding period and the August sale date resulted in an average gain of $13.60/cage for clammers in 1997 and 1998 and $57.73/cage in 2000. Simple culture techniques can be used to increase the value of the live harvest of soft-shell clams along the coast of Maine. Clam impoundments may be a way for communities that co-manage the public clam resource with the state's marine resource agency to generate funds to pay for traditional management schemes, as well as enhancement programs that employ hatchery-reared juveniles. In addition, an indirect benefit of clam impoundments might be to create spawner sanctuaries since animals are impounded during the time when gamete release occurs.     

Effects of stocking density and feeding duration in cage‐cum‐pond‐integrated system on growth performance,water quality and economic benefits of Labeo victorianus (Boulenger 1901) culture

We evaluated the effect of varying cage stocking density (60, 90 and 120 fish m^?3) and feeding duration (10, 30 and 60 min) in a cage‐cum‐pond‐integrated system on growth performance, water quality and economic benefits in Labeo victorianus culture. Interactions between stocking density and feeding duration significantly (P < 0.05) affected the fish growth performance and yields in the cages‐cum‐pond system. Stocking density of 60 fish m^?3 resulted in the highest growth in cages and in ponds regardless of the feeding duration, but produced lower yields than at stocking density 90 fish m^?3_. The lowest Apparent Food Conversion Ratio (AFCR) in cages occurred at stocking density of 60 fish m^?3 and feeding duration of 30 min. Growth performance in the open ponds declined with increased feeding duration of the caged fish. Survival in cages and in the open ponds decreased with increased cage density, but was not affected by feeding duration. Low dissolved oxygen were recorded, at stocking density of 120 fish m^?3, the lowest DO occurred when feeding of caged fish lasted 60 min. Growth performance, water quality and economic benefits in Labeo victorianus culture positively respond to interaction between stocking density and feeding durations.     

浅谈水产健康养殖监管

为促进我省水产养殖持续健康发展,增强水产品质量安全意识,形成从源头到餐桌完整的水产品管理链条,切实保障水产品质量安全。2010年一2012年通过对我省沿黄地区网箱养殖场的监管,主要采取网箱标准化养殖技术、把好三关、建立五项制度、落实六项措施的监管方法,更进一步提高水产品质量安全监督管理体系。     

波浪作用下双层网底鲆鲽网箱水动力特性的数值模拟

根据有限单元法建立了波浪作用下双层网底网箱的受力运动模型,通过数值计算求解双层网底的位移与倾角。先将上层网底与下层网底的计算值进行比较,然后,将双层网底网箱中下层网底与单层网底网箱开展对比分析。计算结果显示,在波浪周期内,双层网底网箱的2层网底能保持相对平行的状态。2层网底的位移与最大倾角随着波高与周期的增大而增加,并且2层网底的倾斜方向一致。在相同波浪条件作用下,下层网底的水平位移大于上层网底,二者垂直位移差异较小,下层网底最大倾角值大于上层网底。研究发现,当波高为15 cm、周期为1.4 s时,双层网底网箱的2层网底的倾角相差最大,但并未发生接触碰撞,网底可以保持相对稳定。此外,双层网底网箱的下层网底的最大位移值小于单层网底网箱,最大倾角值大于单层网底网箱。研究表明,当波浪一定时,双层网底网箱的最大锚绳力均大于单层网底网箱。