On amphidromy, a distinct form of diadromy in aquatic organisms

Amphidromy is a distinctive form of diadromy that involves some fish, decapod crustaceans and gastropod molluscs. Characteristic elements in amphidromy are: reproduction in fresh water, passage to sea by newly hatched larvae, a period of feeding and growing at sea usually a few months long, return to fresh water of well‐grown juveniles, a further period of feeding and growing in fresh water, followed by reproduction there. This life‐history strategy is observed in numerous fish species, primarily in islands of the tropics and subtropics (probably more than 75 species, especially sicydiine gobies), and extends to temperate countries as far as Japan in the north and New Zealand in the south. There has been considerable confusion about the nature of amphidromy and its distinctiveness from anadromy, another category of diadromy. The return to freshwater of small juveniles of amphidromous fishes is functionally and strategically different from the return of large mature adults, as happens in anadromy. The strategy is recognized as distinctive by numerous fish biologists who work with amphidromous fishes, although it has tended to be rejected or ignored by others, typically those who have no personal experience with them.     

Phytase-producing bacteria in the digestive tracts of some freshwater fish

Isolation and enumeration of phytase‐producing bacterial flora in the foregut and hindgut regions of the gastrointestinal tracts of 10 culturable freshwater teleosts of different feeding habits, namely rohu (Labeo rohita), catla (Catla catla), mrigal (Cirrhinus mrigala), bata (Labeo bata), kalbasu (Labeo calbasu), Nile tilapia (Oreochromis niloticus), climbing perch (Anabas testudineus), common carp (Cyprinus carpio), silver carp (Hypophthalmichthys molitrix) and grass carp (Ctenopharyngodon idella), have been carried out. Microbial culture of the gut mucosa on selected nutrient media following the enrichment culture technique was performed for bacterial isolation. The bacterial isolates were screened on the basis of their enzyme‐producing ability. The bacterial population on the tryptone soya agar (TSA) plate was maximum in the hindgut region of bata, followed by mrigal and minimum in the foregut region of Nile tilapia. In modified phytase screening medium (MPSM), phytase‐producing strains were recorded at higher densities in the foregut region of mrigal and grass carp and minimum in the foregut region of bata. In case of the hindgut, maximum phytase‐producing strains were present in grass carp and mrigal and minimum in rohu. In general, in MPSM, the bacterial population was lower in the hindgut region of all the 10 species of fish examined. The phytase‐producing ability of the selected 31 strains (16 from the foregut and 15 from the hindgut region) was determined by clearing zones on phytate‐containing plates. Among these isolates, 22 strains (12 from the foregut and 10 from the hindgut region) were selected as potent phytase producers according to a quantitative enzyme assay. The highest phytase activity was observed in the bacterial strains LF1 and LH1 isolated from the fore and the hindgut regions of rohu respectively. Both the strains were identified as Bacillus licheniformis on the basis of phenotypic characteristics as well as 16S rDNA sequence analysis.     

Natural and artificially-induced habitat complexity and freshwater fish species composition

Abstract  The effects of habitat complexity, induced by construction of artificial reefs, on the fish assemblages in the Barra Bonita reservoir, Brazil, and in the lotic zone immediately below the dam were studied. Four artificial reefs were constructed in each habitat at variable distances from the shore. Multiple correspondence analysis showed that the factors distance from the shore and type of habitat were determinants for the group formation, and artificial reefs had a lesser effect. Fish species composition was about the same at locations with and without reefs.     

Issues for the conservation and management of Falkland Islands freshwater fishes

• 1. The Falkland Islands, in the cool‐temperate south‐western Atlantic Ocean, have an impoverished freshwater fish fauna, with only two indigenous species certainly present there: the Falklands minnow, Galaxias maculatus, and the zebra trout, Aplochiton zebra. Additional species whose presence there is uncertain are the southern pouched lamprey, Geotria australis, and the Patagonian puyen, Galaxias platei. Brown trout, Salmo trutta, were introduced in the mid‐20th century, and sea‐migratory (diadromous) populations are widespread.
• 2. Distributions of zebra trout and brown trout, particularly, are complementary, suggesting that brown trout are having detrimental impacts on zebra trout. Zebra trout have suffered massive decline over the past few decades and remain largely in restricted areas that brown trout have not yet invaded.
• 3. Owing to their sea‐migratory habits, it can be expected that brown trout will eventually invade all significant streams on the Falkland Islands. This raises issues of serious concern since zebra trout are also probably sea‐migratory, and therefore need access to and from the sea to complete their life cycles. Therefore, any streams accessible to zebra trout are potentially accessible also to brown trout, raising the spectre that eventually brown trout will invade all the streams where zebra trout persist.
• 4. The existence of landlocked populations of zebra trout provides some form of protection from brown trout invasion, though a landlocked stock does not represent the full behavioural and genetic diversity of zebra trout in Falkland's waters, and must be regarded as a last resort means for conservation.

Copyright © 2001 John Wiley & Sons, Ltd.     

Spawning, early development and first feeding in the gobiid fish Priolepis nocturna

The reproductive behavior, embryonic development and early larvae of Priolepis nocturna are described. Three pairs of P. nocturna began spawning 41 days after acquisition and maintained a 5–10 day spawning cycle lasting beyond several months. Spawning was initiated by the female who signaled her readiness to spawn by displaying to the male. Egg clutch size averaged 1578 ± 51.23 eggs and ranged from 268 to 3121. Egg length averaged 0.82 ± 0.01 mm total length (TL) and ranged from 0.75 to 0.90 mm. Egg width averaged 0.51 ± 0.51 mm total width (TW) and ranged from 0.49 to 0.52 mm. Fertilized eggs were ovoid in shape and attached to the ceiling of provided shelters via adhesive filaments at the proximal end. Hatching rates averaged 97.3 ± 0.51% and ranged from 91.9 to 99.8%. Larvae measuring 1.89 ± 0.04 mm TL hatched 121 ± 0.5 h post fertilization and did not rotate position prior to hatching. Skeletal elements of the chondrocranium were simplistic and dominated by the hyoid, hyomandibulosymplectic cartilage, ethmoid and Meckel's cartilage in first feeding larvae. No elements were added to the cranial architecture by 5 days post hatch (DPH) when larvae measured 2.05 ± 0.04 mm TL. First feeding larvae consumed only dinoflagellates and tintinnids suggesting that feeding was constrained by a poorly developed feeding mechanism. Embryology and larval development are described to 5 DPH.     

On size and growth in freshwater fish

Patterns of growth and size achieved in freshwater fish are examined with relation to the issues of indeterminate and determinate growth and asymptotic growth. Various authors suggest minimum, average and maximum sizes attained by fish, variously pointing to very small gobies and very large sharks, with most fish being about 150 mm long. Growth in fish is distinctive in that typically it continues throughout life, even though it becomes slower with increasing age and the onset of sexual maturity. Growth rates and size achieved by fish are highly flexible and subject to both genetic and environmental controls, so that size reached may vary with environmental variables such as water temperatures and food availability (both food abundance and prey types and sizes). Frequency distributions of 5 disparate freshwater fish faunas (Papua-New Guinea 267 species and tropical; North America 709 species and subtropical to Arctic; Australia 176 species and tropical to temperate; New Zealand and Great Britain 27 and 39 species and both warm to cool temperate) closely resemble distributions generated by the theoretical model of Hutchinson & MacArthur, and also data on diverse faunas. Frequency distributions in these faunas are closely similar, with a majority of species being small. This similarity would seem to suggest a general explanation. However, examination of the freshwater fish fauna of North America suggests that, rather than showing a predominance of large fish in the Arctic, the fauna has more large fish towards the tropics, though the proportion of large fish there is lower owing to the proliferation of small species in the tropics and a paucity of them towards the Arctic. Analysis shows a shift in the size composition of the fauna with latitude and shows that the general pattern for the whole of North America consists of a composite series of rather different patterns. This suggests that there is probably no meaningful general explanation of the overall patterns seen in these diverse and disparate faunas and that the similarity in overall size distributions between freshwater fish faunas of North America, New Guinea, Australia and New Zealand are of little ecological or evolutionary significance. The generality of Cope's rule is questionable, especially for fish, in which dwarfing and/or evolution towards smaller size are seen to be common phenomena.     

Alien freshwater fish species in the Balkans—Vectors and pathways of introduction

Fish introductions, particularly in areas of high biological diversity and endemism, represent a major threat for biodiversity. In the Balkan Peninsula, 60 fish species have been introduced to date, of which 36 have become naturalized in inland waters. Since the Balkans are one of the world's 35 biodiversity hot spots, this large presence of alien fish species poses a serious threat for the stability of freshwater ecosystems and the survival of the native ichthyofauna and of aquatic biodiversity in general. The motivation for the introductions, and the historical timeline, varies among the Balkan states. Despite recent attempts to implement and align legislation aimed at preventing the introduction of potentially invasive species, and the implementation of rigorous controls of introductions and increased protection of open waters, the majority of current introductions remain intentional, primarily via aquaculture. This review article provides a historical overview of freshwater fish introductions, the motivation behind them and the current distribution of alien freshwater fishes in the Balkans. The ecological implications and future perspectives concerning alien fish species in the region are also discussed.     

Particle size distribution of wastes from freshwater fish farms

Waste water treatment on freshwater fish farms is problematic as waste material and water flows can vary greatly on a daily basis, and, in terms of effluent standards, fish farm effluent represents a dilute waste water output. A study was undertaken to investigate in detail the nature of the waste outputs under field conditions. Waste water samples were split by meshes into the following size ranges: >200μm, 200-100μm, 100-60μm, 60-30μm and <30μm. Waste water quality parameters, suspended solids (SS), biochemical oxygen demand (BOD₅) and total phosphorus (TP) were examined for each size range at two freshwater fish farm sites in Scotland, as part of a wider investigation into waste water quality of aquaculture operations. Results indicated that during periods of peak waste output i.e. tank cleaning, approximately 80% of BOD₅ and SS was present in a particle size range of 100-60μm, but only 66% of TP transport occurred in this size range. At other times, low levels (≤40%) of entrapment of wastes by the chosen meshes was observed, suggesting a reversion to predominantly dissolved material transport. Compared against a larger data set of outflow concentrations obtained from another section of the study, maximum removal rates of 46%, 48% and 30% for BOD₅, SS and TP respectively were determined. The implications for waste water treatment at fish farms are discussed.     

Native and introduced fish community structure in a freshwater swamp forest: Implications for conservation and management

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Effective monitoring of freshwater fish

Freshwater ecosystems constitute only a small fraction of the planet's water resources, yet support much of its diversity, with freshwater fish accounting for more species than birds, mammals, amphibians or reptiles. Fresh waters are, however, particularly vulnerable to anthropogenic impacts, including habitat loss, climate and land use change, pollution and biological invasions. This environmental degradation, combined with unprecedented rates of biodiversity change, highlights the importance of robust and replicable programmes to monitor freshwater fish. Such monitoring programmes can have diverse aims, including confirming the presence of a single species (e.g., early detection of alien species), tracking changes in the abundance of threatened species, or documenting long‐term temporal changes in entire communities. Irrespective of their motivation, monitoring programmes are only fit for purpose if they have clearly articulated aims and collect data that can meet those aims. This review, therefore, highlights the importance of identifying the key aims in monitoring programmes and outlines the different methods of sampling freshwater fish that can be used to meet these aims. We emphasize that investigators must address issues around sampling design, statistical power, species’ detectability, taxonomy and ethics in their monitoring programmes. Additionally, programmes must ensure that high‐quality monitoring data are properly curated and deposited in repositories that will endure. Through fostering improved practice in freshwater fish monitoring, this review aims to help programmes improve understanding of the processes that shape the Earth's freshwater ecosystems and help protect these systems in face of rapid environmental change.     

Influence of larval and juvenile life history on age at first maturity in two tropical amphidromous fish species

This study investigates how age at first maturity of two tropical amphidromous species Sicyopterus lagocephalus (Pallas, 1770) and Cotylopus acutipinnis (Guichenot, 1863) varies in relation to their larval and juvenile life history. Reproductive stage was estimated based on histological observation of ovaries of more than 200 females of each species caught monthly over 1 year. The age of fish was estimated by interpreting the daily increments deposited on otoliths during the oceanic larval phase, and the juvenile phase in the river. The age at first maturity was approximately 9 months for S. lagocephalus and 7 months for C. acutipinnis, corresponding to approximately 70–130 and 90–130 days after they returned to freshwater respectively. For both species, the time spent in freshwater before maturity was significantly influenced by the duration of the pelagic larval stage at sea (PLD) and the season of return in freshwater. Individuals with a long PLD, or returning in freshwater during the warmer season, maturated faster once in freshwater. This reproductive advantage may minimise the risk of extirpation due to catastrophic events at each generation and thus probably benefits amphidromous species living in very unpredictable tropical rivers.     

南美白对虾淡化养殖中的鱼虾混养模式

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An accessory lateral line in some New Zealand and Australian galaxiids (Teleostei: Galaxiidae)

Abstract— Many New Zealand and Australian galaxiids have bilateral accessory lateral lines along the dorso-lateral trunk that consist of widely spaced neuromasts from head to dorsal fin. Dietary studies show that many species feed extensively on terrestrial foods. Some of them are also nocturnally active. The accessory lateral line may assist these fish in locating terrestrial foods at the surface of the water, and perhaps in avoiding predators. Species that lack the accessory lateral line are principally diurnal, mid-water, shoaling species, or small, slender, cryptic, riffle-dwellers.     

Morphological changes during the transition from freshwater to sea water in an amphidromous goby,Sicyopterus lagocephalus (Pallas 1770) (Teleostei)

The widely distributed amphidromous goby Sicyopterus lagocephalus needs drastic change of habitat to fulfil its life cycle: adults live and spawn in rivers, where eggs hatch into prolarvae that have to reach the sea to acquire characteristics of planktonic larvae. Postlarvae return to rivers where they recruit and grow to the adult reproductive stage. Here, we describe the prolarval stages, namely from hatching to first contact with sea water, as well as the first marine larval stages. The observations were made under experimental conditions. We described 3 prolarval substages in freshwater (L1a–L1c). Prolarvae present a slight but visible ontogenetic development in freshwater, during which the yolk sac begins to reduce, the pigmentation increases on the body and in the eyes, and the lenses appear, although the eyes are not functional. Prolarvae need to reach the sea in a maximum of 96 h to pursue their development. Their transfer in sea water at a salinity of 36.5 induces important morphological modifications (i.e. yolk sac full absorption, appearance of pectoral fins, migration of the eyes in anterolateral position of the head, opening of mouth and anus), enabling the organisms to adapt to their new environment. This marine stage is divided into two substages: L2a corresponding to the organisation of the morphological structures adapted to the marine environment and L2b during which these morphological structures become functional. Whether it is in freshwater or sea water, the duration of the substages depends on the water temperature, but is similar for all individuals for a given temperature.     

青藏高原淡水渔业资源及其开发前景

一、青藏高原的水生态环境1、气候与水系青藏高原耸立在中纬度西风带中，海拔较高、气候寒冷、昼夜温差大、降雪较丰富、空气稀薄、多风少雨、降水量不均衡、光照充足以及太阳辐射强等，形成了其独特的高原气候特点。这些特点对生长于青藏高原的淡水鱼类，不仅能影响其形态和生理结构，更对该地区鱼类的生理代谢过程产生诸多影响。青藏高原地区的河流有长江、黄河、雅鲁藏布江、澜沧江、怒江等。湖泊有青海湖、托索湖、鄂陵湖、扎陵湖、西金乌兰湖、可可西里湖、乌兰乌拉湖、库赛湖、卓乃湖、米提江占木错、多尔索洞错、纳木错、错拉、其香…     

淡水鱼产品保鲜技术研究现状

淡水鱼产品中不饱和脂肪酸含量较高,比畜肉和禽肉更容易被氧化,且鱼体细菌繁多,容易引起鱼肉蛋白的腐烂变质,因此淡水鱼产品的防腐保鲜一直是食品行业内的热点研究课题。本文主要介绍目前国内外普遍采用的淡水鱼产品保鲜技术,主要包括低温保鲜技术、包装保鲜技术、辐射杀菌保鲜技术、涂膜保鲜技术以及化学方法保鲜技术。     

First isolation of hirame rhabdovirus from freshwater fish in Europe

A rhabdovirus was isolated in cell culture inoculated with tissue material from diseased grayling, Thymallus thymallus (L.), originating from a fish farm affected by a mortality episode in Poland. Diagnostics tests showed that the virus was not related to novirhabdoviruses known in Europe, nor to vesiculovirus‐like species, except perch rhabdovirus (PRhV) with which it shared moderate serological relations. However, RT‐PCR with PRhV probes gave negative results. To identify the virus, a random‐priming sequence‐independent single primer amplification was adopted. Surprisingly, two of the obtained sequences exhibited a high identity (>99%) with hirame rhabdovirus (HIRRV), a novirhabdovirus usually found in fish in marine Asiatic countries, for instance Japan, China and Korea. The full‐length sequence of the phosphoprotein gene (P) demonstrated a higher identity of the present isolate with HIRRV from China compared with the Korean isolate. An identical viral sequence was also found in brown trout, Salmo trutta trutta L., affected by mortalities in a second farm in the same region, after a likely contamination from the grayling farm. To our knowledge, this is the first report of HIRRV in Europe, and in two hosts from fresh water that have not been described before as susceptible species.     

中国淡水鱼类寄生虫研究七十年

寄生虫是水产养殖中最主要的病原类群之一,对鱼类苗种直至成鱼各个阶段的危害都十分严重。我国的鱼病学即是从鱼类寄生虫的研究发端并逐步发展起来的。本文从病原生物学、生态学、药物学、免疫学四个方面回顾了我国淡水鱼类寄生虫自新中国建立初期至今70年间(1953年—2023年)的研究历程和已取得的成绩,并对未来的发展趋势和前沿热点进行了展望。本文为从事鱼类寄生虫学以及水产其他相关研究的读者提供了关于中国鱼类寄生虫研究的历史、现在发展水平和未来发展动向等较为全面的素材。     

Assessment of year class strength in freshwater recreational fish populations

A method for determining relative year class strength (YCS) in unexploited freshwater fish populations from individual surveys, based on reconstruction of the mortality schedule of the target population, is described. The method was tested against traditional approaches of assessment of YCS and the limitations and applicability discussed. The method is useful for analysing the factors regulating YCS in freshwater fisheries.     

Reducing the mortality of freshwater turtles in commercial fish traps

• 1. Mortality of air‐breathing vertebrates has been recognized for some time as a significant risk in Australian inland fisheries. There has often been conflict between the desires of fishers to maximize catches of their target species and the implementation of effective methods to reduce nontarget bycatch.
• 2. Two trials were conducted to evaluate the effectiveness of modifications to fish traps designed to prevent the capture of freshwater turtles (Emydura macquarii) and to facilitate their release. The first study evaluated the use of 100 mm exclusion rings to prevent turtles entering eel traps. The second study assessed two configurations of a carp trap designed to release the accidental catch of turtles.
• 3. Eel traps fitted with 100 mm exclusion rings significantly reduced the turtle bycatch, with no significant difference being observed between mean size of eels captured in traps fitted with exclusion rings and traps without rings.
• 4. The trials on the modified carp trap confirmed that they effectively retained carp and released a majority (77%) of turtles over a 4 h period. Turtles retained in the carp traps were significantly longer than those that found their way out of the trap.
• 5. This study demonstrates the different approaches that can be taken to achieve a reduction in non‐target bycatch associated with traps, and illustrates the importance of exploiting both the physical and behavioural differences of the target and non‐target species in order to develop appropriate gear designs that effectively restrict the entry, or facilitate the release, of bycatch species.

Copyright © 2004 John Wiley & Sons, Ltd.