Dietary essentiality of ascorbic acid in rohu larvae: Quantification with ascorbic acid enriched zooplankton

Carp larvae, like any other fish larvae dependon natural food during first few days of theirlife. In nursery conditions, high mortality andslow larval growth are of common occurrence;sub-optimal nutrition might be a possiblereason for such consequences. To improve thesituation the effect of feeding ascorbicacid-enriched live food on survival, growth,tissue biochemical composition includingascorbate level was evaluated in first feeding(3 days old) larvae (av. wt. 2.2 mg) of therohu carp, Labeo rohita (Ham.) for aperiod of 15 days (temp. 28.6 ± 1 °C)under natural photoperiod. The larvae (stockingdensity 10 l^–1) were offered enriched andnon-enriched zooplankton ad libitumfollowing a rigid schedule with four feedingregimes, each having 3 replicates. In treatmentT₁, non-enriched zooplankton (Moina,Daphnia, Cyclops, Diaptomus) and in T₂,T₃, T₄ ascorbic acid enriched (12 henrichment) zooplankton [@10%, 20% and 30%ascorbyl palmitate (AP) inclusion in diet ofzooplankton] were offered. Highest survival(90%) and growth (9563% live weight gain)could be seen in T₃ group and the lowestin T₁ (62% survival and 805% live weightgain), thus confirming the dietary essentialityof ascorbic acid for rohu larvae. Therequirement has been shown to be 1409 µg/gdry diet. Whole body tissue analyses for crudeprotein, total lipid and RNA: DNA ratiofollowed the same trend as that of growthresponse and percent survival. Significantpositive correlation (r = 0.949 and 0.861) couldbe found with muscle RNA/DNA ratio and muscleRNA content with specific growth rate indifferent treatments. Significant differencewas found in tissue ascorbate levels betweenenriched plankton fed groups, being highest in T₃. Such live foodmediated vitamin transfer might be an effectivemeans to provide higher plane of nutrition forhigh survival and rapid growth for rohu larva.     

Comparison of environmental conditions in two representative oyster farming areas: Hiroshima Bay,western Japan and Oginoham a Bay (a branch of Ishinomaki Bay), northern Japan

ABSTRACT:   Sea water environmental conditions over annual cycles were investigated and compared between two oyster farming areas, western Hiroshima Bay and Oginohama Bay (a branch of Ishinomaki Bay) in Miyagi Prefecture, to appropriately manage oyster culture or more efficiently utilize farming areas. The environmental parameters of temperature, salinity, nutrient concentrations (NO₂–N, NO₃–N, NH₄–N, PO₄–P, and SiO₂–Si) and size-fractionated chlorophyll- a (<0.2, 2–20, >20µm), and abundances of microzooplankton were measured in each bay at the surface, and 2 and 5 m depth layers. Differences in the annual mean values and results with monthly paired Student's t -tests showed that salinity was lower, and temperature, nutrient (especially PO₄–P) and chlorophyll- a concentrations, and abundance of microzooplankton, were higher in Hiroshima Bay than in Oginohama Bay. Differences in environmental conditions between inshore and offshore areas of each bay suggest that inflows of river water in western Hiroshima Bay and sea water from offshore had the most significant effects on the environmental conditions. It is concluded that such oceanographic and biological differences strongly affect the oyster farming system, especially regarding the optimum usage of offshore areas in Summer under clean, cold and stable seawater conditions, rather than food quantity in Hiroshima Bay, and under more abundant food conditions in Oginohama Bay.     

Breeding and larval rearing of threatened, endemic fish stonesucker, Garra ceylonensis (Bleeker)

This study was aimed to develop captive breeding and nurture the young of stonesucker (Garra ceylonensis, Bleeker), a small threatened freshwater fish species endemic to Sri Lanka. Breeding of stonesucker was possible under indoor conditions without hormonal stimulation. They were single spawners having a fecundity of 562±176 eggs per fish (total length of 7.9±0.6 cm) with an egg size of 770–1877 μm. Duration of development stages were, egg to hatchling 36–48 h, hatchling to postlarva stage 3–4 days, postlarva to juvenile stage 5–64 days and adult stage in 300–365 days at 26–28°C. Juveniles exhibited bottom dwelling habit in 70–75 days. Postlarva fed with formulated feed exhibited the highest growth (P<0.05) compared with live diets, Artemia and microworm (Anguillula sp.). Although the juveniles revealed a significantly high growth performance (P<0.05) with swine liver diet up to day 45 compared with formulated feed and combination of detritus and plankton, formulated feed exhibited an increase in growth from day 50. Therefore, formulated feed could be used for rearing of postlarva and juvenile stages without any live feeds.     

刺参养殖池塘不同粒级浮游生物呼吸率和初级生产率的研究

于2008年1—6月对大连壹桥海洋苗业股份有限公司4个刺参Apostichopus japonicus养殖池塘不同粒级浮游生物的呼吸率和初级生产率进行了测定。结果表明:(1)小型、微型及超微型浮游生物的呼吸率平均值分别为0.31、0.63、0.80 mg/(L.d)(以O2计,下同),分别占各粒级浮游生物总呼吸率的17.88%、36.10%和46.02%;小型、微型及超微型浮游植物生产率平均值分别为0.27、0.59、0.64mg/(L.d),占各粒级浮游植物总生产率的18.18%、38.98%和42.84%;小型、微型及超微型浮游生物呼吸率占相应粒级浮游植物生产率的比例分别为113.90%、107.24%、124.39%。(2)>200μm、20~200μm、2~20μm和<2μm的4个粒级浮游植物叶绿素a含量的平均值分别为0.75、0.65、3.08、1.26μg/L,分别占总叶绿素a含量的13.15%、11.30%、53.63%和21.92%。     

北太平洋(160°E～170°E)大型柔鱼渔场的初步研究

本文根据1997年6月～7月北太平洋（16°E～170°E）海域柔鱼探捕调查的资料，对渔场形成的海洋环境条件进行了初步分析。160°E～170°E海域的大型柔鱼渔场主要由亲潮策3和第4分支与黑潮的第4和第5分支交汇形成，特别是在深层（100米水层）的暖水域前端形成。其表层水温一般为11～13°，100米水层水温约为9～10℃。其中167°E～170°E海域的渔场较为稳定，可供北太平洋鱿钓船的前期生产。中心渔场形成时常有浮游生物层。浮游生物层越厚实，渔获量越高，但有关浮游生物层的形成原因需作进一步的研究与探讨。     

Effect of horizontal advection induced by intrusion of the Kuroshio water on plankton biomass in the spring fishing period of shirasu on the Pacific coast of Japan

ABSTRACT:   This study explored the fundamental process that controls interannual change in plankton biomass on the Pacific coast of Japan, focusing on the spring period of shirasu fishery. A 1-D model of primary production revealed that the strength of horizontal advection induced by warm water intrusion from the Kuroshio into the Pacific coast is the most critical for plankton biomass compared with other factors such as diffusion and production. This conclusion was also confirmed by a sensitivity analysis of the model.     

天津天嘉湖渔业生物学基础调查

按照《内陆水域渔业自然资源调查手册》对天嘉湖水化学、浮游生物、底栖动物、鱼类状况进行了调查。结果表明:天嘉湖水质良好,适合鱼类生长;鱼类天然饵料生物量相对较低,不适合鲢鳙生长;主要渔获物为人工放养的异育银鲫Carassiusauratusgibelio.,今后应依据其自然条件以放养异育银鲫为主,少放鲢鳙;放养12cm以上的大规格的鱼种,提高成活率和回捕率;控制凶猛鱼类的种群数量。     

Recent changes in the trophic structure of the Black Sea

During the past few decades, the Black Sea has been subjected to various human impacts that have led to changes in the ecology of this inland sea. River runoff has introduced high levels of certain heavy metals and other toxic substances as well as detergents. Ship traffic has led to the introduction of new species, and fishing pressures have also altered the ecology of the area.
This paper reviews major ecological changes over the past 40 years. An increase in nutrients has caused eutrophication, with outbursts of phytoplankton blooms and changes in the species composition of these algae. Small-sized zooplankton species and gelatinous zooplankton have become more common, while many of the herbivorous copepods have decreased in abundance or have disappeared. The introduction of the predatory ctenophore Mnemiopsis leidyi in the 1980s has had significant impact on the plankton community and has led to a sharp decline in anchovy stocks. Decreased water transparency has led to a loss of macrophytic algae, except in shallow waters, and to a subsequent decline in the zoobenthos associated with this flora. Eutrophication has also led to decreased oxygen concentrations in the near-bottom water due to large amounts of decomposing phytoplankton, and regions of hypoxia and anoxia now appear on the shelf, with consequent reduction in benthic populations of invertebrates and demersal fish. The numbers of fish species harvested commercially have fallen from 26 to 5, but the total catch has increased, owing to increases in abundance of small fish (e.g., sprat) and horse mackerel, and to increased fishing effort.     

大房郢水库浮游生物群落结构变化与环境因子关系研究

为了更好地了解合肥市饮用水源地水生态环境状况,于2020年夏季、秋季、冬季及2021年春季对大房郢水库的水质、浮游植物和浮游动物进行监测,对比浮游生物群落现存量与历史变化,并使用冗余分析（RDA）以及蒙特卡洛置换检验探究环境因子对浮游生物群落的影响。结果表明,研究区域浮游植物以蓝藻门为主要优势种属,密度及生物量较2005年分别增加37.7%和7.0%,浮游动物以桡足类为主要优势种,密度较2005年大幅度下降了77.5%,生物量多样性增加了47.8%,影响浮游生物群落结构的主要环境因子为NH3-N、T（温度）、pH和TN。此外,研究也揭示了季节变化对水库浮游生物的物种组成影响小,但对浮游生物的丰度及多样性影响显著。