Food and feeding habits of Tilapia aurea (Steindachner) (Cichlidae) in Lake Kinneret (Israel)

An analysis of the food of 274 specimens of Tilapia aurea (Steindachner), which had been collected in Lake Kinneret, showed that this species is mainly a zooplankton consumer.A study of the quantitative dynamics of the food components in the course of a year has proved that the species in question feeds more intensely in spring, this being the time when zooplankton forms are more abundant in the water of the lake. Vegetable detritus, mixed with plankton and benthos forms, served as additional and alternative food.The lack of clearly positive degree of food component selectivity, as well as the low values of the intestine repletion index and of the condition coefficient, account for the slowness in growth of Tilapia aurea in Lake Kinneret.The low values of the growth and feeding indices are due, according to the authors, to the pressure brought to bear by the other local fish species, which are competitors for the same food.     

Food and feeding habits of Tilapia zillii (Gervais) (Cichlidae) in Lake Kinneret (Israel)

Analysis of the gut content of 329 specimens of T. zillii (Cichlidae) collected from Lake Kinneret, has shown great variation in the sorts of food.A study of seasonal dynamics has proved the prevalence in the food of Chironomida pupae (Diptera) in winter and spring and of zooplankton forms in summer and autumn. The additional food consisted of the various groups of algae, the most frequently found being Cyanophyta (100%) and Pyrrophyta (64.16%). An extremely voraceous species, it consumes — while searching for its preferred food — anything that comes its way in the water: algae, scraps of macrophytes, autochthonous and allochthonous insects, and forms of benthic origin, such as Nematoda, Ostracoda, Porifera and Chironomida (larvae).The satiation index is high (between 4.08 and 5.63), in contradiction to the low values of the coefficient of condition (between 3.05 and 3.51), and with the slow rate of growth in Lake Kinneret. The main food of Tilapia zillii, consists of arthropod species with a chitin content (which is eliminated unchanged) of more than 50% of the total weight, and this may account for the poor exploitation of the trophic base.This species of fish may be considered as being detrimental to others (i.e. commercially important species) because of its successful competition for food, and not, as is often incorrectly assumed, because it is an aggressive consumer of their spawn and fry.     

叶尔羌高原鳅胚胎发育与胚后发育观察

采用形态学和生态学方法,对叶尔羌高原鳅[Triplophysa(Hedinichthys)yarkandensis(Day)]胚胎发育和胚后发育阶段全过程进行观察、拍照并测量。结果显示:叶尔羌高原鳅,卵微黏性,略有沉性,受精卵呈卵圆形,卵径为(0.60±0.052)mm,在水温(20.0±1.0)℃下,历时65 h 34 min完成整个胚胎发育分为7个生理阶段过程;胚后发育主要根据卵黄囊、体色、鼓鳔和须的变化分为仔鱼期、稚鱼期、幼鱼期。初孵卵黄囊仔鱼全长(2.0±0.65)mm,出膜后7 d,卵黄囊吸收完毕,完全消失;初孵仔鱼继续培育至16日龄,仔鱼鳃盖后缘鼓鳔明显长出,须清晰可辨,体色加深,心脏红色素明显,体色与成体相似,标志后期仔鱼发育完全进入稚鱼期,此时鱼苗全长(8.0±0.45)mm;培育至30日龄,仔鱼鼓鳔完全,鳃盖张合明显,身体透明特征消失,稚鱼阶段完成发育进入幼鱼期,此时全长达(13.0±0.55)mm,其外部形态和生态习性均与成鱼相似。试验中,卵黄囊长度(LY)和出膜天数(D)的关系式:LY=0.0286D2–0.0636D+3.1196(R2=0.9050);用直线方程拟合卵黄囊长度(LY)和卵黄囊仔鱼全长(LT)的关系式:LY=–1.315LT+5.368(R2=0.8199);拟合卵黄囊仔鱼全长(LT)和出膜后仔稚鱼天数(D)的关系式:LT=–0.0263D2+0.5113D+1.6169(R2=0.9890)。本研究旨在通过了解叶尔羌高原鳅的早期发育特征为该物种的保护和增殖对策提供科学依据,并对其苗种生产提供理论指导。     

Global conservation status and research needs for tarpons (Megalopidae), ladyfishes (Elopidae) and bonefishes (Albulidae)

We assessed the taxonomic diversity, geographic distributions, life history, ecology and fisheries of tarpons, ladyfishes and bonefishes (members of the subdivision Elopomorpha), which share many life history and habitat use characteristics that make them vulnerable to environmental and anthropogenic stresses in coastal environments. This assessment of Red List status for the International Union for the Conservation of Nature reveals three species considered near threatened or vulnerable, three species of least concern, and 11 data‐deficient species. Although the taxonomy of tarpons appears stable, it is less so for ladyfishes and bonefishes. In aggregate, these species are distributed circumtropically and foray into temperate zones. Although they spawn in marine habitats, larvae of many species disperse into estuarine habitats, which are declining in area or degrading in quality. Several species support high‐value recreational fisheries, or culturally important small‐scale commercial and artisanal fisheries. Nonetheless, no formal stock assessment exists for any species, so improved data collection, information sharing and assessment techniques should facilitate socio‐economic development of individual fisheries. Catch‐and‐release recreational fisheries that promote conservation of tarpon and bonefishes in some regions are promising models to improve the conservation status of these fishes elsewhere, as well as the economic development of these fishing communities. Most tarpons, ladyfishes and bonefishes likely face significant challenges from anthropogenically mediated habitat loss and alteration, and several are vulnerable to both habitat degradation and overfishing. Broader protection and enhancements to fisheries habitat in all regions will benefit these as well as many other coastal fishery species.     

Using fatty acid markers to distinguish between effects of salmon (Salmo salar) and halibut (Hippoglossus hippoglossus) farming on mackerel (Scomber scombrus) and whiting (Merlangius merlangus)

Presence of coastal aquaculture activities in marine landscapes is growing with impacts on the wild fish that share these habitats. However, it is difficult to disentangle subsequent ecological interactions between these activities and marine fish communities. We evaluated the impact of both salmon and halibut farms on mackerel (Scomber scombrus) and whiting (Merlangius merlangus) sampled near sea cages using condition indices and fatty acid (FA) biomarkers. Results of the stomach content analysis indicated that mackerel and whiting consumed waste feed which was also reflected in their modified FA profiles. Both mackerel and whiting had elevated levels of FAs that are of vegetable oils origin. The use of vegetable oils as replacement for marine oils is a lot more common in salmon farming than halibut farming. Additionally, the overall effects of the two fish farms were more pronounced in whiting than in mackerel sampled near the sea cages. By allowing discrimination between sources of trophic interactions, this method could lead to more informed decisions in managing different farming activities.     

鱼体内环境激素ＤＭＰ和ＤＥＰ的检测方法

建立同时检测鲫(Carassuys auratus Linnaeus)血浆和肌肉中邻苯二甲酸二甲酯(DMP)和邻苯二甲酸二乙酯(DEP)的高效液相色谱方法,进行初步的代谢动力学研究.血浆样品经液-液萃取,肌肉样品经液-液萃取和固相小柱处理后,以乙腈:水= 40:60(V/V)为流动相,流速1.0 mL/min,采用SHIMADZU ODS柱(150 mm×4.6 mm; i.d., 5 μm)色谱柱分离.测定鲫经口染毒后血浆和肌肉中DMP和DEP的浓度.结果表明,标准曲线线性范围为0.05～10.0 μg/mL,线性关系良好(r>0.99),定量限为0.05 μg/mL,回收率95%以上,日内变异系数和日间变异系数均低于15%.经口染毒48 h内,鲫血浆和肌肉中均能检测到DMP和DEP的残留.该法操作简便、快速、灵敏、准确,已经初步用于鲫血浆和肌肉中DMP和DEP的代谢动力学和残留研究.     

鱼体内环境激素DMP和DEP的检测方法

建立同时检测鲫(Carassuys auratus Linnaeus)血浆和肌肉中邻苯二甲酸二甲酯(DMP)和邻苯二甲酸二乙酯(DEP)的高效液相色谱方法,进行初步的代谢动力学研究。血浆样品经液-液萃取,肌肉样品经液-液萃取和固相小柱处理后,以乙腈∶水=40∶60(V/V)为流动相,流速1.0mL/min,采用SHIMADZU ODS柱(150mm×4.6mm;i.d.,5μm)色谱柱分离。测定鲫经口染毒后血浆和肌肉中DMP和DEP的浓度。结果表明,标准曲线线性范围为0.05~10.0μg/mL,线性关系良好(r>0.99),定量限为0.05μg/mL,回收率95%以上,日内变异系数和日间变异系数均低于15%。经口染毒48h内,鲫血浆和肌肉中均能检测到DMP和DEP的残留。该法操作简便、快速、灵敏、准确,已经初步用于鲫血浆和肌肉中DMP和DEP的代谢动力学和残留研究。     

泰山赤鳞鱼生物学特性及其人工繁殖技术

泰山赤鳞鱼与富春江的鲥鱼、青海湖的湟鱼、渤海的油鱼和弓鱼并称为我国“五大贡鱼”,近年来由于生态环境的恶化而使这一珍贵鱼种濒临灭绝。为了保护和开发利用这一珍稀的物种资源,笔者经过多年精心研究,取得了泰山赤鳞鱼人工繁殖实验的成功,通过撰写该稿希望能引起业内有关人士的重视。一、泰山赤鳞鱼生物学特性1.形态泰山赤鳞鱼为小型鱼类,多数个体体重为50g~120g,个别个体体重可达150g,成鱼全长20cm左右,体窄长且略侧扁,头顶钝圆,口下位呈弧形横裂。有上颌须2对,上吻部略向体前方突出,下颌有角质缘,各鳍无棘。在自然环境中,体背侧面沙黄…     

Carbohydrate Metabolism of Vitellogenic Follicles and Eggs of Serranus cabrilla (Serranidae) and Mullus barbatus (Mullidae) and of Embryos of Sparus aurata (Sparidae)

The present study compared the carbohydrate metabolism of pelagic eggs of three marine species, Serranus cabrilla (Serranidae), Mullus barbatus (Mullidae) and Sparus aurata (Sparidae). In particular, in Serranus cabrilla and Mullus barbatus the changes in carbohydrate metabolism from the vitellogenic follicle stage to the ovulated egg stage (final maturation of the egg) were investigated, and in Sparus aurata the changes from the unfertilized egg stage to the late-embryo stage just before hatching were observed. In mature, unfertilized eggs of these three species the qualitative and quantitative composition of carbohydrates, enzymes and metabolites were similar, indicating no differences in carbohydrate metabolism. Glycolysis, gluconeogenesis and the pentose phosphate pathway occurred in the follicles and eggs. From the vitellogenic follicle stage to the mature egg stage glycolytic activity was constant in S. cabrilla and M. barbatus, while the activity of the pentose phosphate pathway and of gluconeogenesis decreased. Quantitative carbohydrate composition changed as the levels of hexose, ketose, 6-deoxyhexose, uronic acid and fructose-6-phosphate increased from the vitellogenic follicle stage to the mature egg stage, while the levels of D-glycerate-2-phosphate and phosphoenolpyruvate decreased. In S. aurata, the investigated parameters of carbohydrate metabolism were similar between unfertilized eggs and eggs in the first cleavage stage. From the first cleavage stage to the late embryo stage the levels of hexose, 2-deoxyhexose, ketose, ribose, uronic acid and phosphoenolpyruvate increased, while the levels of D-glycerate-2-phosphate decreased.     

褐牙鲆(♀)×犬齿牙鲆(♂)杂交F1及其亲本肌肉营养成分分析与比较

褐牙鲆(Paralichthys olivaceus)为东亚地区重要的海水养殖鱼类,在中国、日本和韩国海水养殖业中占有重要的地位.目前,褐牙鲆经过连续多代缺乏选择的人工繁育和养殖,造成养殖群体种质发生退化,生长速度和抗逆性下降,极大制约了牙鲆养殖业发展.以选育生长迅速、抗逆性强、饵料转化率高的牙鲆类养殖新品种为目的,作者对褐牙鲆(♀)×犬齿牙鲆(Paralichthys dentatus)(♂)的杂交育种进行了研究.本实验对褐牙鲆(♀)×犬齿牙鲆(♂)杂交F1及其亲本肌肉营养成分进行测定.结果显示,杂交F1含水率显著低于双亲(P＜0.05),粗蛋白含量显著高于双亲(P＜0.05),粗脂肪含量介于二者之间;杂交F1的氨基酸总量、必需氨基酸、非必需氨基酸、半必需氨基酸与鲜味氨基酸总量都显著高于褐牙鲆与犬齿牙鲆(P＜0.05);脂肪酸含量方面,脂肪酸总量、不饱和脂肪酸总量3种鱼由高到低排列顺序为褐牙鲆、犬齿牙鲆、杂交F1,三者饱和脂肪酸总量差异不显著(P＜0.05).对3种鱼肌肉的营养品质进行了评价,杂交F1的必需氨基酸指数EAAI(90.30)明显高于褐牙鲆(77.75)与犬齿牙鲆(79.34),在蛋白质品质上表现出一定杂种优势.上述结果表明,杂交F1的肌肉具有蛋白和氨基酸含量较高、脂肪酸含量较低的特点.     

Comparative gonad histology and semen quality of normal (XY) and neo‐males (XX) of Atlantic salmon (Salmo salar)

With an overarching objective of improving the hatchery production of Atlantic salmon (Salmo salar) all‐female progeny, this study comparatively evaluated the reproductive parameters between normal (genotype XY) and neo‐males (genotype XX). Four normal (XY) and seven neo‐ (XX) males, from the same brood stock, distinguished by their ability to or lack of expressing semen, respectively, were comparatively evaluated. The left testicular lobe was used for histomorphometric analyses, while the right for semen collection and sperm quality analyses. Histomorphometric observations revealed that neo‐male testes are irregularly shaped, and have poorly formed seminiferous ducts, higher proportions of interstitial tissue and lower gonadosomatic index (p < .05). In addition, hypertrophied and cyst forming Sertoli cells were found in these individuals which collectively appear to form a physical barrier, precluding the semen collection by standard stripping techniques and reducing sperm quality. Particularly, semen motility (80.69 ± 2.4% and 57.2 ± 36.5% for XY and XX respectively) and duration of motility (99.31 ± 28.03 s and 66.84 ± 23.83 s for XY and XX respectively) of neo‐males were most compromised (p < .05). Interestingly, the TUNEL assay indicated no signs of apoptotic tissue suggesting that the histological differences may relate to delayed physiological/sexual maturity of neo‐males.     

Impact of freshwater input and wind on landings of anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus) in shelf waters surrounding the Ebre (Ebro) River delta (north-western Mediterranean)

Time series analyses (Box–Jenkins models) were used to study the influence of river runoff and wind mixing index on the productivity of the two most abundant species of small pelagic fish exploited in waters surrounding the Ebre (Ebro) River continental shelf (north‐western Mediterranean): anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus). River flow and wind were selected because they are known to enhance fertilization and local planktonic production, thus being crucial for the survival of fish larvae. Time series of the two environmental variables and landings of the two species were analysed to extract the trend and seasonality. All series displayed important seasonal and interannual fluctuations. In the long term, landings of anchovy declined while those of sardine increased. At the seasonal scale, landings of anchovy peaked during spring/summer while those of sardine peaked during spring and autumn. Seasonality in landings of anchovy was stronger than in sardine. Concerning the environmental series, monthly average Ebre runoff showed a progressive decline from 1960 until the late 1980s, and the wind mixing index was highest during 1994–96. Within the annual cycle, the minimum river flow occurs from July to October and the wind mixing peaks in winter (December–April, excluding January). The results of the analyses showed a significant correlation between monthly landings of anchovy and freshwater input of the Ebre River during the spawning season of this species (April–August), with a time lag of 12 months. In contrast, monthly landings of sardine were significantly positively correlated with the wind mixing index during the spawning season of this species (November–March), with a lag of 18 months. The results provide evidence of the influence of riverine inputs and wind mixing on the productivity of small pelagic fish in the north‐western Mediterranean. The time lags obtained in the relationships stress the importance of river runoff and wind mixing for the early stages of anchovy and sardine, respectively, and their impact on recruitment.     

Ontogenetic changes in the diet of the black-stripe minnow Galaxiella nigrostriata (Shipway, 1953) (Galaxiidae) and the salamanderfish Lepidogalaxias salamandroides (Mees, 1961) (Lepidogalaxiidae)

Abstract –  Similarities in the diets of larval, juvenile and adult black-stripe minnow ( Galaxiella nigrostriata ) and salamanderfish ( Lepidogalaxias salamandroides ), collected from ephemeral pools in south-western Australia during the mid-wet, late-wet and dry seasons, were assessed. During the mid-wet season, both intra- and interspecific competition for a diminishing food supply was minimised through differences in prey utilisation by the various developmental stages of both species. During the late-wet season, the pools contained only juvenile G. nigrostriata and juvenile and adult L. salamandroides , the diets of which were vastly different. A shift towards terrestrial fauna by G. nigrostriata and the ingestion of greater proportions of larger benthic prey taxa by L. salamandroides minimised interspecific competition for food at a time when densities of zooplanktors were rapidly declining. Timing differences in the onset of aestivation ensures that no interspecific competition for food occurs during the dry season.     

Substitution effect of sea tangle (ST) (Laminaria japonica) with tunic of sea squirt (SS) (Halocynthia roretzi) in diet on growth and carcass composition of juvenile abalone (Haliotis discus,Reeve 1846)

Substitution effect of sea tangle (ST) with tunic of sea squirt (SS) in diet on growth and carcass composition of juvenile abalone was determined. One thousand four hundred and seventy abalones were distributed into 21 containers. Six formulated diets in triplicate were prepared. A 200 g/kg ST was included into the ST0 diet. The 200, 400, 600, 800 and 1000 g/kg of ST were substituted with the same amount of tunic of SS, referred to as the ST200, ST400, ST600, ST800 and ST1000 diets, respectively. Finally, Undaria was prepared to compare effect of the formulated diets on performance of abalone. The experimental diets were fed to abalone for 16 weeks. Weight gain of abalone fed the ST400 diet was higher than that of abalone fed the ST0, ST600, ST800 and ST1000 diets and Undaria. Weight gain of abalone fed the formulated diets was higher than that of abalone fed the Undaria. The chemical composition of the carcass of abalone was affected by dietary substitution of ST with tunic of SS. In conclusion, ST could be completely substituted with tunic of SS without retardation in performance of abalone. Abalone fed the ST400 diet substituting 400 g/kg ST with tunic of SS achieved the best growth.     

Karyotype analysis of Oreochromis mortimeri (Trewavas) and Sarotherodon melanotheron (Rüppell)

The karyotypes of both Oreochromis mortimeri (Trewavas) and Sarotherodon melanotheron (Rüppell) are shown to consist of 22 pairs of chromosomes (2n = 44). In O. mortimeri, the karyotype is composed of 9 sm/st and 13 t chromosomes. In the case of S. melanotheron, the karyotype is composed of 15 sm/st, 2 m and 5 t chromosomes. The karyotypes of these species are therefore similar to those of the majority of other tilapia species, with that of S. melanotheron being considerably different from that previously reported for this species.     

Salinity studies on the clams Katelysia rhytiphora (Lamy) and Tapes dorsatus (Lamarck)

The estuarine clams Katelysia rhytiphora (Lamy) and Tapes dorsatus (Lamarck) require salinities of 20–45%₀ for survival and of 25–35%₀ and 30–40%₀ respectively for best growth. The highest 24-h algae clearance rates for K. rhytiphora and T. dorsatus were observed at salinities of 25–35%₀ and 30–35%₀ respectively. Neither species survived longer than 7 days at salinities <20%₀ and they can. therefore, only be grown in the high-salinity parts of estuaries. The salinity requirements of these clams should be a primary consideration when selecting farming sites. Other species of bivalves that tolerate lower salinities should also be considered for farming in brackish water areas of New South Wales, Australia.     

Incorporation and metabolism of (n-3) and (n-6) polyunsaturated fatty acids in phospholipid classes in cultured turbot (Scophthalmus maximus) cells

The incorporation and metabolism of various (n-3) and (n-6) polyunsaturated fatty acids (PUFA) supplemented to the culture medium was investigated in a turbot cell line (TF). The distribution, and the occurrence and extent of further metabolism of incorporated PUFA via desaturation/elongation mechanisms in specific phospholipid classes was determined from the different fatty acid compositions. The cells contained Δ6 and Δ4 desaturase activities but were generally deficient in C18–20 elongase activity. Δ5 Desaturase activity was generally masked by this deficiency but was present. The compositional data indicated that there was a high degree of specificity between individual phospholipid classes and particular fatty acids probably driven by the specificities of the acylating enzymes. The highest percentages of the supplemented acids were generally observed in the phosphatidic acid/cardiolipin fraction (PA/CL), suggesting a role for PA in the incorporation of the supplemented acids into the phospholipid pool. PI had a characteristic composition consistent with a putative role as a pool of precursor fatty acid for eicosanoid synthesis. Mechanisms were evident for generating and/or maintaining this composition.     

卵形鲳鲹碱性磷酸酶和酸性磷酸酶的分布及其低温保存

测定了卵形鲳鲹（Trachinotus ovatus）的碱性磷酸酶（AKP）和酸性磷酸酶（ACP）在不同器官和肌肉中的活性;将样品分别置于4℃、-20℃和-80℃下保存3 d、7 d、15 d和30 d,研究不同保存温度和保存时间对样品中AKP和ACP酶活性的影响。结果表明,在卵形鲳鲹胃中未检测到AKP活性,其他器官中均检测到AKP活性,AKP活性大小顺序依次为后肠〉幽门盲囊〉肾〉中肠〉肝〉前肠〉心〉肌肉;ACP在卵形鲳鲹体内分布较广,所测器官中均有ACP活性,其活性大小顺序为肝〉肌肉〉后肠〉中肠〉幽门盲囊〉肾〉心〉前肠〉胃。低温保存试验结果表明,AKP和ACP在4℃和-20℃下保存,时间越长,活力越低;在-80℃下保存,AKP和ACP活力在30 d内基本稳定,只有幽门盲囊的AKP和ACP在长时间保存后活力明显下降。     

Hematological Parameters and Blood Cell Morphology of Male and Female Schizothorax (Racoma) davidi (Sauvage)

The aim of this study was to obtain a basic knowledge of the hematology of Schizothorax (Racoma) davidi (Sauvage). The results showed that red blood cell and white blood cell counts as well as mean cellular hemoglobin concentration were significantly higher in females than in males, while mean cell volumes were significantly lower in females than in males. No significant differences were seen in other hematological parameters in relation with gender. Under light microscope, erythrocytes (mature and immature), leukocytes (neutrophils, lymphocytes, and monocytes), and thrombocytes were distinguished. Mature erythrocytes were ellipsoidal cells with oval, central nucleus. Neutrophils contained banded or segmented nuclei. Small lymphocytes had a very thin rim of basophilic cytoplasm. Monocytes often possessed vacuoles in their cytoplasm. Thrombocytes existed in several forms with relatively large nucleus surrounded by a pink‐stained or hyaline cytoplasm. The percentage of the different leukocytes revealed predominance of neutrophils and small lymphocytes, followed by monocytes and large lymphocytes. The neutrophil percentages of each stage showed that metamyelocyte accounted for the most, followed by banded neutrophils. This investigation could be used for evaluation of the health status of cultured male and female S. davidi and will provide early detection of clinical pathology.     

Incorporation and metabolism of (n-3) and (n-6) polyunsaturated fatty acids in phospholipid classes in cultured rainbow trout (Salmo gairdneri) cells

The incorporation and metabolism of various (n-3) and (n-6) polyunsaturated fatty acids supplemented to the culture medium was investigated in the rainbow trout cell line, RTG-2. The distribution, and the occurrence and relative extent of further desaturation and elongation of the incorporated acids was determined in individual phospholipid classes by analysis of the fatty acid compositions. RTG-2 cells exhibited Δ6 and Δ5 desaturase activities whereas Δ4 desaturase activity was almost totally absent. The percentage of precursor acids was greatest in the phosphatidic acid/cardiolipin fraction (PA/CL), suggesting a role for possibly PA in the initial incorporation of these acids into the phospholipid pool. The compositional data indicated that individual intermediates and products of the desaturation pathways were associated with specific phospholipid classes probably via mechanisms depending upon the specificities of the acylating enzymes. The composition of phosphatidylinositol (PI) and the tightly controlled mechanisms for generating/maintaining it are consistent with a role for this phospholipid in providing precursor fatty acid for eicosanoid synthesis.