Nutrient composition and metamorphosis success of Atlantic halibut (Hippoglossus hippoglossus, L.) larvae fed natural zooplankton or Artemia

Atlantic halibut larvae were fed docosohexanoic acid- (DHA) selco enriched Artemia (RH-cysts) or wild zooplankton in duplicate tanks from first-feeding and 60 days onward. The zooplankton were collected from a fertilized sea water pond and consisted mainly of different stages of Eurytemora affinis and Centropages hamatus . There were no differences in survival, or in growth during the first 45 days of feeding, between larvae fed the two prey items, but the larvae fed Artemia showed much higher incidence of malpigmentation and impaired eye migration than larvae fed zooplankton. The prey organisms contained similar amounts of dry matter and protein, but Artemia was higher in lipid and glycogen than the zooplankton. Larvae fed Artemia were higher in both glycogen and lipid than the zooplankton-fed larvae towards the end of the feeding period. There were large differences between the prey organisms in the concentrations of essential fatty acids (% of total fatty acids) which was reflected in the fatty acid composition of the larval body. It is concluded that the macronutrient composition of Artemia in the present study was probably within the optimal range for promotion of growth and survival in young Atlantic halibut. The concentration of n-3 HUFA, and especially DHA, is however, very much lower in enriched Artemia than in copepods, and may be one of the factors triggering developmental errors in Atlantic halibut.     

鱼类早期生活史研究与其进展

鱼类早期生活史的研究，主要涉及卵和仔鱼发育，仔鱼最佳饲养条件、饵料密度、营养、生长、临界期、饥饿、捕食、环境耐力和毒性反应等和渔业密切相关的诸因子，是鱼类自然资源繁殖保护和养殖业苗种培育的基础。近二、三十年来，鱼类早期生活史研究已成为水产科学的一个崭新领域，在国际上受到广泛重视并迅速发展。国际海洋开发理事会(ICES)曾三次举行鱼类早期生活史学术讨论会，     

鱼类细菌性败血症发病鱼池细菌数量及致病性气单胞菌的初步研究

本文对细菌性败血症发病鱼池细菌数量及气单胞菌的数量、溶血性及致病力进行了研究。结果表明:水温在28.5℃以下时,细菌数量与水温基本成正比,发病池与不发病池的细菌数量无显著性差异;水体中广泛存在气单胞菌,其占水体总菌量比例随水温的上升而升高;发病池及未发病池中均存在能产生hec毒素和不产生hec毒素的嗜水气单胞菌株,两者数量上无显著差异;水体中存在血清型为TPS—30及PBJS—76的嗜水气单胞菌,且大多数对鱼体有毒力,以5×10~7CFU/尾腹腔注射,可使试验鱼大部分或全部发病死亡。     

Growth and production of the Amazonian tambaqui in fixed cages under different feeding regimes

Experimental culture of the native Amazonian fish tambaqui, Colossoma macropomum, in fixed cages was carried out over a period of 8 months, in Lake Urubu (Rio Grande do Norte, Brazil), to assess the viability of fixed cage culture of tambaqui and to test the influence of diet on growth rates. Nine synthetic net cages (1 m³) were each stocked with 45-day-old fish (mean weight 3 g; mean total body length 51 mm) at a density of 34 fry m^–3. During the first 2 months of culture, fish were fed a balanced formulated feed on an as-fed basis at the rate of 5% body weight day^–1. During months 3–8 this continued for fish in treatment 1 while those in treatment 2 were fed tropical regional fruits, on a wet weight basis at the rate of 5% body wt day^–1. Fish in treatment 3 were given no supplementary feed. Monthly biometric measurements were made on all fish. Fixed cage fish culture was shown to be a viable and simple technique. Survival in all treatments was 100%. With balanced supplementary feed, production was 14.4 kg m^–3, compared with 4.9 kg m^–3 and 2.1 kg m^–3, respectively, in the treatments where fish were fed with fruits and were not given any supplementary feed.     

Electromechanical effects of acetylcholine on the atrial tissues of the cultured tilapia (Oreochromis nilotica × O. aureus)

The effects of acetylcholine (ACh) on the action potential and twitch force of atrial tissues isolated from 15 tilapia (Oreochromis nilotica × O. aureus) were studied by means of conventional microelectrode techniques. In isolated whole atrium or sinoatrial tissue, scattered pacemaker-like cells with spontaneous diastolic depolarization were found mainly near the sinoatrial junction but also occasionally throughout the atrial wall. However, most of the atrial cells recorded were myocardial fibers as judged by a stable diastolic potential and a markedly reduced action potential duration (APD) in response to low concentrations of ACh (0.1–1 M). The shortening in APD in atrial myocardial fibers was correlated with a significant fall in twitch force in the atrial preparations. ACh at high concentrations (10–300 M) decreased moderately the APD and the slope of diastolic depolarization of the pacemakers and prolonged the spontaneous cycle length but did not induce hyperpolarization. The negative chronotropic action of ACh was competitively inhibited by atropine, a muscarinic antagonist. The means (± SEM) negative logarithm of the dissociation constant (pK_b or pA₂ value) for atropine against the ACh action on muscarinic receptors were 9.10 (± 0.13) (n = 6), similar to those values obtained in mammalian atria. The present findings indicate that while the negative inotropic effects of ACh in tilapia atria are comparable to those observed in mammalian hearts, unique electrophysiological responses to ACh exist in different types of tilapia atrial cells.     

养殖密度对鱼类福利影响的研究进展I．死亡率、生长、摄食以及应激反应

养殖密度影响鱼类福利是鱼类生理生态学、福利学和种群生态学研究中的关键问题,已受到各国学者的关注。文章综述了养殖密度影响鱼类福利的主要研究进展,讨论了鱼类死亡率、生长、摄食以及应激反应等福利指标随养殖密度变化的规律及其描述方法；在此基础上,对鱼类福利指标随不同放养密度变化规律的研究以及应用前景进行了展望。     

Cryopreservation of dead fish spermatozoa several hours after death of Indian major carp, Labeo rohita and its successful utilization in fish production

Cryopreservation of semen collected from dead fishes showed that it is possible to use it for fish production. We humanely killed individuals of the Indian major carp rohu, Labeo rohita and stored at different temperature regimes of 31 °C, 0 °C, − 10 °C and − 30 °C till 8 h. At every one hour interval semen from these fishes were collected by Pasteur pipette and evaluated for sperm yield/kg body weight, motility, pH, spermatocrit (%) and sperm count. The semen having suitable characteristics such as; 70% spermatocrit or above and motility index of 4 or above was cryopreserved by following a specific protocol. The cryopreserved semen of the dead fishes was stored for 7 days and then thawed in a water bath at 37 °C for 50 s. It was found that up to 8 h, spermatozoa of rohu were viable when stored at 0 °C or − 10 °C. Sperm collected after 8 h of fish death and maintained at 0 °C was the best stored condition that showed 30% larval survival. The spermatozoa collected 8 h after fish death was mostly normal as observed under scanning electron microscope and the total length of rohu spermatozoa was 25-30 μm. The hatchlings produced with this cryopreserved semen grew normally and juvenile fishes of rohu could be produced. This study suggests that germ cells such as spermatozoa of dead fishes can be cryopreserved and utilized for restoration of a species. It has the potential use in cryo-conservation of endangered fishes, restoration of animals through fertilization and genetic manipulation studies.     

The status of host fish populations and fish species richness in European freshwater pearl mussel (Margaritifera margaritifera) streams

• 1. The status of host fish populations and fish species richness was investigated at 36 sites of 20 extant freshwater pearl mussel populations, including the drainages of the Elbe, Danube, Rhine, Weser, Aulne, Kemijoki and Tuuloma in Germany, the Czech Republic, France and Finland, by carrying out comparative electrofishings.
• 2. Brown trout (Salmo trutta f. fario) were found to be the available host fish for pearl mussels in all except one of the streams investigated with mean densities of 2861 ha^?1 (range 0–8710 ha^?1) and a mean biomass of 119 kg ha^?1 (range 0–478 kg ha^?1). Streams that had been frequently stocked with brown trout had higher trout biomass and densities of host fish than natural populations, but trout stocking had no positive effect in two of the streams investigated.
• 3. Fish species richness ranged from 2 to 16 species per stream and showed a negative correlation with host fish biomass and host fish densities. Undisturbed oligotrophic pearl mussel headwater streams usually only yielded a low number of fish species. Habitat degradation can reduce competitiveness of specialized trout and result in an increased abundance of ubiquitous or atypical species.
• 4. A link between the lack of juvenile pearl mussels and a lack of suitable host fish was only rarely observed. Functional pearl mussel populations with relatively high numbers of juveniles had significantly lower densities and biomass of host fish than pearl mussel populations without recent recruitment.
• 5. This study suggests that 0+ host fish are not necessarily required to sustain functional pearl mussel populations. Low densities of host fish can be compensated by the higher glochidia carrying capacity of older host fish with limited previous contact with pearl mussel glochidia, by the long reproductive period of mussels, and by low mortality rates of juvenile mussels during their post‐parasitic phase.

Copyright © 2005 John Wiley & Sons, Ltd.     

Linking geomorphic character,behaviour and condition to fluvial biodiversity: implications for river management

• 1. The River Styles^® framework is a geomorphic approach to the classification of river types, assessment of the physical condition of rivers, and planning of physical rehabilitation. However, the linkages between River Styles and aquatic biodiversity conservation are still only weakly developed.
• 2. In this study, 41 sites in the Bega River basin in New South Wales, Australia, were classified according to River Style and geomorphic condition, and surveyed for four biological assemblages: diatoms, aquatic and semi‐aquatic macrophytes, aquatic macroinvertebrates and fish.
• 3. Each assemblage differed significantly among River Styles. However, in the case of diatoms and fish, these differences could be accounted for by geographic clustering of sites in the same River Style, and a tendency for River Styles to occupy particular altitudinal zones and sizes of streams. This result was attributed to the overriding influences of water quality on diatoms and of altitude‐related variation in water temperature and distance from the ocean on fish. For macrophytes and macroinvertebrates, geomorphic river type appeared to exert a direct influence, probably via variation in physical habitat characteristics.
• 4. Geomorphic condition, judged as good, moderate or poor by reference to the inferred natural condition of each River Style, was also significantly associated with differences in biological assemblages other than fish. Twice as many taxa appeared to favour sites in good geomorphic condition as favoured sites in poor condition. Many of the taxa associated with sites in poor condition are alien taxa introduced to Australia since European settlement.
• 5. These findings imply that protection of reaches that are in good geomorphic condition is likely to be critical for the maintenance of indigenous biodiversity, and that rehabilitation of geomorphic condition can assist in the rehabilitation of native riverine biota.

Copyright © 2006 John Wiley & Sons, Ltd.     

Stand basal area as an index of tree competitiveness in timber intercropping

To derive optimal benefits from intercropping timber, farmers should make important initial decisions on tree species and planting density with a good understanding of their tradeoffs. Complex and data-intensive models used by researchers should be supplemented with simpler models based on easily measured parameters and easily understood competition functions. In experiments in the Philippine uplands, growth parameters of three popular farm-forestry species (Eucalyptus deglupta, E. torelliana, and Paraserianthes falcataria) were measured, along with intercropped and non-intercropped yields of maize and vegetables. The commonly used forestry parameter of stand basal area had a significant negative correlation with intercrop yields (as a percentage of non-intercropped yields). The slope of the regression line differed between species; in this study, percent yield loss per unit stem basal area growth was in the order E. deglupta > E. torelliana > P. falcataria. The relationship between stand basal area and intercrop-yield decline was tested on an independent data set from China. Intercrop yields had significant negative correlations with stand basal area of Paulownia elongata. We propose that adaptive tree-screening trials evaluate competitiveness in addition to evaluating growth and mortality. Stand basal area may be better suited to this task than more mechanistic indices such as leaf-area index as it is easy to measure, calculate, and understand, and it may serve as a better index of total (aboveground + belowground) competition. Basal area is also directly related to tree volume, and allows farmers to more easily evaluate the economic tradeoffs between tree growth and intercrop-yield declines. This revised version was published online in June 2006 with corrections to the Cover Date.