Larviculture of the painted river prawn Macrobrachium carcinus in different culture systems

The objective of this study was to evaluate different hatchery systems used for the larviculture of the Macrobrachium carcinus based on survival, larval development and production of post-larvae. The experimental culture was carried out in three phases designated as Phase I (Zoea VI to VIII – Z_{VI – VIII}), Phase II (Zoea VIII to X – Z_{VIII – X}), and Phase III (Zoea X to PL – Z_{X – PL}), with densities of 30, 27.5 and 25 larvae / L, respectively. The M. carcinus larvae (Z_VI) were reared in four culture systems, two being open (Greenwater – GW and Clearwater – CW) and two being closed (Biofloc – BFT and Bio-filter – RAS), distributed in twelve 10 L plastic containers, filled with 20 ppt brackish water, equipped with constant aeration, and water circulated by air lift and heated with thermostat (∼30 °C). The GW treatment was maintained with Chlorophyceae algae in the density of 3–5 × 10⁵ cells/mL. In the CW, the water was previously filtered through a 5 μm mesh screen, sterilized with 10 ppm active chlorine and, dechlorinated with vitamin C and subjected to aeration for 24 h. The BFT received water rich in bioflocs that was matured prior to the experiment and used molasses as a source of organic carbon. In the RAS, the culture water circulated through an external “Dry-Wet” biological filter. The feeding was carried out ad libitum four times daily, alternating a wet diet formula with a commercial diet, which was supplemented with newly hatched Artemia nauplii at a rate of 40–50 per larvae/day. Temperature, dissolved oxygen and pH were monitored daily and the salinity two times per week. Total ammonia, nitrite, nitrate, orthophosphate, alkalinity, total suspended solids, chlorophyll-a, COD and BOD were also analyzed. The best water quality (P < 0.05) was obtained in the RAS, with 0.49 (±0.38), 0.23 (±0.22), and 9.0 (±1.5) mg/L of TAN, NO₂-N and NO₃-N, respectively. In the GW, the nitrogen species showed high fluctuations and higher concentrations at 2.32 (±1.68), 3.53 (±3.53) and 18.2 (±12.9) mg / L of TAN, NO₂-N and NO₃-N, respectively. Considering the three phases (Z_{VI – PL}), the overall survival was 0.03, 1.97, 2.23 and 17.32 % for the BFT, CW, GW and RAS, respectively. When considering the phases separately, the survival in Phase I (Z_{VI – VIII}) was highest in the GW system at 58.7 % while the RAS was the highest in Phases II (Z_{VIII – X}) and III (Z_{X – PL}) at 70.6 % and 60.3 %, respectively. The BFT showed 8.4 (±3.5) PL/L, which was higher (P < 0.05) than that obtained in the RAS (2.8 ± 1.2 PL/L) and the GW (1.3 ± 1.1 PL/L) and similar to that obtained in the CW (5.6 ± 2.0 PL/L). Thus, the larviculture for the M. carcinus may be optimized by adopting a multiphase management strategy, which the intermediate larval stages (Z_{VI – IX}) are reared in the GW system and the final stages (Z_{X – PL}) are reared in the BFT system.     

Influence of storage and drying methods on invertebrate elemental and isotopic measurements

Optimised pre-analytical methods for measuring the chemical properties of soil macro-organisms are needed. We tested the effects of ethanol immersion, freezer storage, and drying method on the reliability of estimates of key stoichiometric elements (carbon [C], nitrogen [N], phosphorus [P]) and abundances of ¹³C and ¹⁵N in samples of crickets (Acheta domestica), cockroaches (Nauphoeta cinerea) and mealworms (larval Tenebrio molitor). Ethanol immersion tended to increase A. domestica C and N, and reduced A. domestica P, relative to the reference treatment (deep freezing and oven drying). For N and P these effects were only present after 28-day ethanol immersion. Nauphoeta cinerea and T. molitor samples were generally unaffected by storage treatments, while δ¹³C and δ¹⁵N were not affected by any storage treatment for any species. Thus, five days of ethanol immersion may be acceptable prior to elemental and stoichiometric analyses of hard-bodied soil invertebrates in comparative studies.     

Modeling the water budget in a deep caldera lake and its hydrologic assessment: Lake Ikeda, Japan

The hydrologic assessment of a lake water budget can be helpful in achieving proper water management and sustainable water use. A model to analyze a lake water budget was developed and verified for Lake Ikeda, Japan. Lake evaporation was estimated by numerical analyses of lake water temperature and the lake energy budget. Inflow from the lake catchment area and leakage from the lake bottom were estimated based on the tank model and Darcy's law, and the model parameters were optimized by the shuffled complex evolution method. The estimated monthly lake evaporation rate is consistent with the evaporation rate estimated by the energy budget Bowen ratio method based on in situ data from 2004 to 2005. Moreover, the calculated time series of daily lake levels agrees well with those of measured lake levels during 1983 to 1999. Thus, the model is useful for evaluating the lake water budget. Numerical analysis reveals seasonal and annual variation characteristics in the water budget components. Precipitation, inflow from the catchment area, and river water supply are generally high during the rainy season from June to July with substantial annual variation. Lake evaporation is greatest in October and least in April, but the annual variation is relatively small. Agricultural water use is relatively high from April to September. There are no marked seasonal changes in leakage and drinking water use. The lake level is generally highest in September and lowest in March, which is characterized by seasonal changes in water budget components. The model was also applied to 17-year simulations under hypothetical hydrologic conditions to examine the effect of water use and agricultural water management on the lake level. Results indicate that river water supply, provided under the agricultural water management system, effectively compensates for the decrease in lake water resulting from agricultural water use.     

The pond's shape matters: differential growth,physiological condition and survival of epibenthic Farfantepenaeus aztecus postlarvae

As a function of the water quality provided by square, circular and oval experimental ponds, the growth, survival and oxygen requirements in epibenthic postlarvae of Farfantepenaeus aztecus were analysed in relation to their routine metabolism and apparent heat increment. Temperature, oxygen concentration, pH and salinity were measured daily in two experimental ponds of each shape. The postlarvae oxygen consumption during two 24‐h cycles, their growth, physiological condition and survival and the productivity in the ponds were estimated. Low values of pH, oxygen concentration and phytobenthos productivity, and reduced postlarvae relative growth and survival were observed in the square ponds. We suggest that the latter results from a deficient water circulation related to the effect of the pond's shape on dissolved oxygen levels and, consequently, on growth and survival. The postlarvae routine metabolism, including feeding, varied between 1.91 and 2.25 mg O₂ h^?1 g^?1 wet weight, whereas the minimum oxygen concentration needed in the ponds is approximately 4.25 mg O₂ L^?1. These conditions were achieved in the oval ponds concurrent with higher survival and growth values, in which individuals distributed randomly, for which we suggest that oval‐shaped ponds could be the most adequate for the culture of this and other penaeid species.     

Spatial integration of freshwater fish markets in the Northern Baltic Sea area

Freshwater fish species and Baltic salmon (Salmo salar) are important to small-scale fisheries in Finland and Sweden. The formerly local markets for these species have expanded as trade has been opened up to international competition. In this study we use cointegration analysis to test the spatial integration of freshwater fish markets in Finland and between Finland and Sweden. The analysed fish species are salmon, perch (Perca fluviatilis), pikeperch (Sander lucioperca), European whitefish (Goregonus lavaretus) and pike (Exos lucius), and the data covers ex-vessel prices from 1993 or 1995 to 2004. We found that the regional prices in Finland were cointegrated. This indicates that the prices are determined on a single market in Finland. Moreover, the study suggests that Finnish and Swedish markets in Baltic salmon, whitefish, pikeperch and perch were partially integrated, while integration of pike markets could not be found. The political implication is that an essential part of the local small-scale fisheries’ operational environment is determined outside the national borders.     

C/N ratio control and substrate addition for periphyton development jointly enhance freshwater prawn Macrobrachium rosenbergii production in ponds

The present research investigated the effect of carbon/nitrogen ratio (C/N ratio) control in ponds with or without substrate addition for periphyton development on production of giant freshwater prawn. C/N ratios of 10, 15 and 20 were investigated in 40 m^− 2 ponds stocked with 2 prawn juveniles (5.023 ± 0.02 g) m^− 2 with or without added substrates for periphyton development. The various treatment combinations of C/N ratio and periphyton substrate addition are abbreviated as ‘CN10’, ‘CN15’, ‘CN20’, ‘CN10 + P’, ‘CN15 + P’ and ‘CN20 + P’, P representing periphyton substrate. A locally formulated and prepared feed containing 30% crude protein with C/N ratio10 was applied. Tapioca starch was used as carbohydrate source for manipulating C/N ratio and applied to the water column separately from the feed. Increasing the C/N ratio from 10 to 20 reduced (P < 0.001) the total ammonia-nitrogen (TAN), nitrite–nitrogen (NO₂–N) and nitrate–nitrogen (NO₃–N) in water column and total Kjeldahl nitrogen (TKN) in sediment. The addition of substrates only influenced the NO₂–N concentration in the water column (P < 0.001). Increasing the C/N ratio raised the total heterotrophic bacterial (THB) population in the water column, sediment and periphyton (P < 0.001). It also increased the dry matter (DM), ash free dry matter (AFDM), and chlorophyll a content of periphyton (P < 0.001). The lowest specific growth rate (SGR), the highest food conversion ratio (FCR), and the lowest protein efficiency ratio (PER) were recorded in treatment CN10 (P < 0.05). The addition of substrates did not influence size at harvest (P > 0.05) but improved the survival from 62.8 to 72% (P < 0.001). Increasing the C/N ratio from 10 to 20 increased the net yield by 40% and addition of substrate increased the net yield by 23%. The combination of C/N ratio control and substrate addition increased the net yield by 75% from 309 (CN10) to 540 (CN20 + P) kg ha^− 1 (120 days)^− 1. This 75% higher production concurred with (1) a lower inorganic nitrogen content in the water column, (2) a higher THB abundance supplying additional single cell protein to augment the prawn production, and (3) an improved periphyton productivity and quality.     

Investigation of Deep-Sea Ecosystems Using Marker Fatty Acids: Sources of Essential Polyunsaturated Fatty Acids in Abyssal Megafauna

Abyssal seafloor ecosystems cover more than 50% of the Earth’s surface. Being formed by mainly heterotrophic organisms, they depend on the flux of particulate organic matter (POM) photosynthetically produced in the surface layer of the ocean. As dead phytoplankton sinks from the euphotic to the abyssal zone, the trophic value of POM and the concentration of essential polyunsaturated fatty acids (PUFA) decrease. This results in pronounced food periodicity and limitations for bottom dwellers. Deep-sea invertebrate seston eaters and surface deposit feeders consume the sinking POM. Other invertebrates utilize different food items that have undergone a trophic upgrade, with PUFA synthesized from saturated and monounsaturated FA. Foraminifera and nematodes can synthesize arachidonic acid (AA), eicosapentaenoic acid (EPA), while some barophylic bacteria produce EPA and/or docosahexaenoic acid. FA analysis of deep-sea invertebrates has shown high levels of PUFA including, in particular, arachidonic acid, bacterial FA, and a vast number of new and uncommon fatty acids such as 21:4(n-7), 22:4(n-8), 23:4(n-9), and 22:5(n-5) characteristic of foraminifera. We suppose that bacteria growing on detritus having a low trophic value provide the first trophic upgrading of organic matter for foraminifera and nematodes. In turn, these metazoans perform the second-stage upgrading for megafauna invertebrates. Deep-sea megafauna, including major members of Echinodermata, Mollusca, and Polychaeta display FA markers characteristic of bacteria, foraminifera, and nematodes and reveal new markers in the food chain.     

崇西潮滩湿地木本工程物种引种的初步研究

崇西湖滩湿地高潮区引种工程物种成活率及生长状况的研究结果表明：（1）根据物种的成活率来看,对潮汐干扰适应性表现最好的物种有落雨杉、沼生栎和喜树;表现较好的有细叶水团花、江南桤木、木麻黄、枫杨、重阳木、鸟桕和白杜;表现一般的有彩叶杞柳、海滨木槿和构树;表现较差的为常青白蜡;不能适应的有美国复叶槭、朴树、榉树、苦楝、枸杞、桑和枣。除了喜树和构树没有变化外,其他工程物种第2年的成活率较第1年都有了不同程度的下降;（2）综合各工程物种引种2年后的生长指标（高度、冠辐和胸径等）,成活的乔木物种中,江南桤木的生长态势最好,生长速度最快,其他生长态势较好的有落雨杉、沼生栎和木麻黄;成活的灌木中,海滨木槿、彩叶杞柳和细叶水团花的生长态势较好;（3）综合引种物种的成活率和生长指标,崇西湿地高潮区在今后大规模营建有林湿地的过程中,江南桤木是应该重点引种的乔木物种,其他推荐的引种乔木还有落雨杉、沼生栎、木麻黄;细叶水团花是最适宜引种的灌木,而彩叶杞柳和海滨木槿可以进行适量的引种,并加以精细的维护和管理,同样可以达到增加景观多样性的效果。     

长江三角洲淡水鱼类区系研究

整理了长江三角洲地区淡水鱼类名录,并对该地区淡水鱼类的区系组成进行了分析。结果表明,长三角地区共有淡水鱼类220种,隶属14目35科109属。该地区淡水鱼类可分为6个区系复合体:中国江河平原鱼类区系复合体,98种;南方热带平原鱼类区系复合体,65种;中印山区鱼类区系复合体,5种;北方平原鱼类区系复合体,5种;北方山区区系复合体,5种;上第三纪鱼类区系复合体,7种。其他种类为河口及洄游性鱼类。长三角地区鱼类区系以东亚特有的江河平原鱼类为主。     

Patterns and impacts of fish bycatch in a scallop dredge fishery

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