Local Fish Farm Research Articles

Lactococcus lactis BFE920 activates the innate immune system of olive flounder (Paralichthys olivaceus), resulting in protection against Streptococcus iniae infection and enhancing feed efficiency and weight gain in large-scale field studies

The protective effect of a food-grade lactic acid bacterium Lactococcus lactis BFE920 against disease of olive flounder (Paralichthys olivaceus) cultivated on a large scale was studied. Initially, antimicrobial activity of L. lactis against several fish pathogens was evaluated in vitro; the probiotic showed strong antibacterial activity against Streptococcus iniae, Streptococcus parauberis and Enterococcus viikkiensis, and moderate activity against Lactococcus garviae. When olive flounders were fed for two weeks with experimental diets containing varying concentrations of L. lactis (1 × 106, 5 × 106, 2.5 × 107 and 1.25 × 108 CFU/g feed), all the experimental feed groups showed 68–77% survival upon challenge with S. iniae. A field-scale feeding trial with L. lactis dietary supplement was conducted in a local fish farm (n = 12,000) for three months, and disease resistance, innate immune parameters and growth performance were evaluated. The average weight gain and feed efficiency were increased up to 6.8% and 8.5%, respectively. At the end of the feeding trial, the olive flounders were challenged with S. iniae. The L. lactis-fed group was protected from S. iniae challenge with a 66% survival rate. This disease protection is due to the flounder's innate immunity activated by the L. lactis administration: increased lysosomal activities and production of IL-12 and IFN-γ. These data clearly indicated that L. lactis BFE920 may be developed as a functional feed additive for protection against diseases, and for enhancement of feed efficiency and weight gain in olive flounder farming.

Stress Modulated Physiological Responses in Nile Tilapia, Oreochromisniloticus, Treated with Non-Ascorbic Acid Supplemented Feed

Stress caused by the aquaculture environment hampers normal growth and immune response of fish and makes them susceptible to diseases. Ascorbic acid (vitamin C), on the other hand, has been known to improve the immune response. Experiments were conducted to investigate the effects of the absence of vitamin C in fish dietgrown in stressed condition induced by crowding. Fish fingerlings were obtained from a local fish farm and were acclimated in the new environment for two weeks. After the acclimation period, fish were maintained in two different conditions: controlled and stressed (density > 50 g/l). Within each condition, fish were further divided into two diet groups, each with two replicates. The experimental groups were fed vitamin C supplemented (1000 mg/kg) feed and the control groups were fed vitamin C free feed for fifteen days. Six fish from each group were sampled to assess the physiological parameters: plasmacortisol, blood glucose, plasma protein, packed cell volume, spleen somatic index, and condition factor. Fish in the stressed conditions showed significantly higher level (p<0.05) of plasma cortisol, blood glucose indicating stress, both of which were reduced when fed vitamin C supplemented diet. Significantly higher (p<0.05) hematocrit concentration was observed in the vitamin C fed group indicating better physiological adaptation.

Paratrichodina africana (Ciliophora: Trichodinidae) of wild and cultured Nile tilapia in the Northern Brazil

The present work morphologically characterizes Paratrichodina africana from the gills of wild and farmed Nile tilapia from Northern Brazil (eastern Amazonia). Ninety fish were captured for parasitological analysis in Macapá, State of Amapá, from a wetland area bathed by the Amazon River commonly called 'Ressaca do Zerão' (n = 52), as well as from a local fish farm (n = 38). Wet smears of the skin and gills of the captured fish were air dried at room temperature and impregnated with silver nitrate by Klein's method for posterior examination of the adhesive disc structures. Total prevalence of parasitism was 16.6% (23% in fish from wetland and 7.8% in farmed fish). Characterized as a small-sized trichodinid, it presented the following measures: 33.2 ± 4.7 µm body diameter, 17.5 ± 2.1 µm adhesive disc, 10.0 ± 0.9 µm denticulate ring, and 22.6 ± 2.0 denticles. Paratrichodina africana reported in this study strongly resembles those described for other localities, but it differs by presenting greater body length. This is the fourth report of P. africana parasitizing a host fish.

Isolation and validation of microsatellite markers from a depleted South African sciaenid species, the dusky kob (Argyrosomus japonicus), by means of the FIASCO/454 approach

The dusky kob (Argyrosomus japonicus) is a large, estuarine-dependent sciaenid fish that has been severely depleted in South African waters and that, in recent years, has received considerable attention from the local fish farming industry. Discovery and application of appropriate molecular markers is necessary to improve the understanding of wild population structure, assist the effectiveness of broodstock and breeding programmes, and ensure monitoring of potential interactions between wild and farmed fish. The present study uses a recently tested approach that combines the FIASCO enrichment protocol with 454 GS-FLX Next Generation Sequencing, to identify large numbers of microsatellite-containing sequences at a low cost and high discovery rate from the dusky kob genome. Following the FIASCO enrichment (targeting specifically tetranucleotide repeats), 2,355 potential tetranucleotide microsatellites (perfect repeat motifs including eight or more repeat units flanked by regions for primer design) were identified from 1/5th of a single 454 lane. From these sequences, a test panel of 60 potential markers was selected for validation. A total of eight (13 %) markers were successfully amplified from a test sample of wild dusky kob individuals and showed high levels of polymorphism (observed heterozygosity per locus ranging between 0.375 and 0.905). Cross-species amplification of seven of these markers was also successfully carried out in another closely related and commercially important South African sciaenid species, the silver kob (A. inodorus). The microsatellite markers developed in the present study are readily available tools suitable to address genetic variability of Argyrosomus species of southern Africa.

Molecular Genetic Analysis of Stomach Contents Reveals Wild Atlantic Cod Feeding on Piscine Reovirus (PRV) Infected Atlantic Salmon Originating from a Commercial Fish Farm

In March 2012, fishermen operating in a fjord in Northern Norway reported catching Atlantic cod, a native fish forming an economically important marine fishery in this region, with unusual prey in their stomachs. It was speculated that these could be Atlantic salmon, which is not typical prey for cod at this time of the year in the coastal zone. These observations were therefore reported to the Norwegian Directorate of Fisheries as a suspected interaction between a local fish farm and this commercial fishery. Statistical analyses of genetic data from 17 microsatellite markers genotyped on 36 partially-degraded prey, samples of salmon from a local fish farm, and samples from the nearest wild population permitted the following conclusions: 1. The prey were Atlantic salmon, 2. These salmon did not originate from the local wild population, and 3. The local farm was the most probable source of these prey. Additional tests demonstrated that 21 of the 36 prey were infected with piscine reovirus. While the potential link between piscine reovirus and the disease heart and skeletal muscle inflammation is still under scientific debate, this disease had caused mortality of large numbers of salmon in the farm in the month prior to the fishermen's observations. These analyses provide new insights into interactions between domesticated and wild fish.

English

A major agricultural sub-sector where achieving food security has become elusive in Nigeria is the fish production subsector. Demand for fish in Nigeria stands at about 1.5 million metric tonnes per annum while domestic production is just 511,700 metric tonnes. The wide gap between demand and supply is attributed to increasing population, improved nutrition, underdeveloped local fish farming potentials and depletion of artisanal sources resulting from unsustainable fishing. The nation spends about N150 billion (US$1billion) annually to bridge the gap between supply and demand. This huge amount spent annually constitutes enormous strain and drain on the nation&rsquo;s foreign reserves especially when the potentials for local production to meet the domestic market and for export exist in abundance. Consequently, several policy measures have been put in place to stimulate local fish farming. Till date, the results from the colossal investment and policy have not yielded the desired results. Hence, this study attempted to examine the factors determining the sustainability of fish farming in Nigeria with a view to stimulating private investment in the sector, meet national market demand through domestic production and export the excess to enhance the income of farmers. Regression and budgetary analyses were used to analyze data obtained from 100 fish farmers in ten local government areas of Osun State. The result showed that the average net income in the study area was N318,640.75 while the gross margin was N457,327.95. The benefit-cost ratio was 1.5 indicating that for every N100 invested, the enterprise yields additional N50. The regression analysis showed that experience of farmers in fish farming, quantity of feed used, access to credit and size of pond were significant determinants of fish farm production in Nigeria. Major challenges confronting fish farming in the study area are lack of access to credit, high cost of inputs and poor extension services. &nbsp; Key words: Fish farming, inland waters, nutrition, employment, poverty, sustainable, pond.

The use of two enrichment forms (Brachionus plicatilis enrichment and rearing water enrichment) with probiotic bacilli spore on growth and survival of Silver carp (Hypophthalmichthys molitrix)

Summary This study was carried out to evaluate the effect of probiotic (Bacillus latrospores and Bacillus licheniformis) on growth and survival of Silver carp larvae (Hypophthalmichthys molitrix). Rotifers (Brachionus plicatilis) were used as live prey vehicle for probiotic transport. They were cultured in sea water with 15 ppt salinity and Nannochloropsis oculata microalgae was used as feed. Five treatments were prepared with three replicates (four experimental treatments and one control). Silver carp larvae were obtained from a local fish farm (Golestan, Iran). Rotifers were filtered from intensive cultivation tanks with 200 rotifer/ml density and then transferred to conical glasses for the enrichment process, and were kept under enrichment conditions for 24 h. Two forms of enrichment were carried out: rotifer biocapsulation and rearing water enrichment. T1 and T2 were fed with biocapsulated rotifers and T3 and T4 were fed non-biocapsulated rotifers. Instead of biocapsulation, the same density of bacteria was injected directly into the rearing water of T3 and T4. T3 (4.4 ± 1.2 mg) and T4 (5.05 ± 1.95 mg) treatments of probiotic injected water had significantly higher growth rates than T1 (2.21 ± 0.94 mg) and T2 (3.9 ± 0.36 mg), (P<0.05). T1 (3.9 ± 1.03 mg) and T2 (3.3 ± 0.36 mg) had higher growth rates than the control (2.21 ± 0.94 mg) and were also significantly different from each other (P<0.05).

Maslinic acid, a natural triterpene, and ration size increased growth and protein turnover of white muscle in gilthead sea bream (Sparus aurata)

Maslinic acid (MA) is a pentacyclic triterpene used, at experimental level, as an additive to stimulate growth, protein-turnover rates and hyperplasia in fish. In this experiment we have studied the effects of feeding with MA at daily fixed ration of 10 g kg−1 of body mass, on growth, protein-turnover rates and nucleic acid concentration in white muscle of gilthead sea bream grown in a local fish farm. The experimental groups contained 0 (control), 50 (MA50) and 100 (MA100) mg MA per kg of diet. Two groups were provided feed ad libitum (control AL and MA100AL), while three were given a fixed ration (control R, MA50R, and MA100R). We have determined the following: growth rate; nucleic acid and protein levels; relative and absolute protein-accumulation (KG, AG), synthesis (KS, AS) and degradation (KD, AD) rate, protein-synthesis capacity (CS), protein-synthesis efficiency (KRNA), protein-synthesis rate per DNA (KDNA) and protein-retention efficiency. At the end of the experiment, higher body weights and muscle growth rates were found in both groups of fish fed with 100 mg MA per kg of diet. Feed-efficiency rate, protein-efficiency ratio and protein productive value, were higher in the MA100AL group than in control AL. Fractional and absolute protein-synthesis and degradation rates in white muscle of MA100AL and MA100R fish were higher than in the control, resulting in a higher protein-accumulation rate and tissue growth. Total DNA content, indicated cell hyperplasia, was higher in MA100AL and MA100R than its respective controls. Studies of optical and electronic microscopy corroborated these results. These findings indicate that MA added to the diet can stimulate the growth, white-muscle protein-turnover rates and tissue hyperplasia in gilthead sea bream.

Investigation of some diseases of carp at Al-Shamiya city/Iraq

The present study was conducted during (March,April,May,June ,July and August-2009) months to investigate some diseases infected the carp fish at Al shamiya city/Diwaniya provence,715 samples of common carp ,grass carp and silver carp were examined from local market and fish farms . The diagnosis based on case history, clinical&amp; necropsy findings , bacterial culture and wet mount . Recorded results shows, there are 46(6.43%) cases of acute and chronic form of heamorrhagic septicemia , 57(7.97%)caeses of bacterial enteritis, 76 (10.63%)of anchor worms( Lernaea),4 (0.56%) of lice infestation, 3 (0.4%) of cestodes and 65 (9%) cases of Diplostomum spp., the total infection are 251(35.1%) from 715 investigated samples. The study showed there are diversity forms of diseases among carp spp. in which the percentage of parasitic infections is the most abundant form of diseases(20.7%) followed by diseases caused by bacterial infections (14.4%) .

Contrasting effects of water stress on wetland‐obligated birds in a semi‐natural Mediterranean wetland

This study evaluated the effects of seasonal water level changes on two foraging guilds of water-related bird species in a remnant coastal wetland of central Italy. Data were obtained by point count method. During the seasonal water-level decrease in wetland channels, the Diversity Index and Species Richness of the entire assemblage dropped significantly between May and July. A significant decrease in the number of species was observed in the middle of May, attributed to decreasing water levels related to natural (climatic) and anthropogenic (local fish farming) causes, and the subsequent drying of surrounding marshes and meadows. A first phenological threshold was observed in May, when the water level decreased to 70 cm in channels. A high species turnover occurred in the entire assemblage during this period. The herbivorous-omnivorous species (Anatidae and Rallidae) and zoophagous species (Ardeidae and Podicipedidae) during the study period exhibited opposite trends in the diversity index values. The diversity index progressively decreased for the herbivorous-omnivorous species in the late spring, while increasing for the zoophagous species, due to a greater availability of food (increased fish density due to decreased water level). These contrasting results are a consequence of ecological and phenological (sedentary vs. migrants) traits of the species belonging to these guilds. These data represent useful information for elaborating management strategies focused on the water level regime in Mediterranean small wetlands in which fish-farming activities also occur.

Detection of DNA damage in fish Oreochromis mossambicus induced by co-exposure to phenanthrene and nitrite by ESI-MS/MS

Mutagenic nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) have been known to arise in the environment through direct emissions from combustion sources and nitration of PAHs, primarily in the atmosphere. In the marine environment, PAHs are one of the classic anthropogenic organic pollutants, while nitrite (NO(2)(-)) is produced naturally via various biological processes like imbalance in nitrification/denitrification or eutrophication and subsequent oxygen depletion from an oversupply of nutrients. In this paper, we report the formation of PAH-DNA adducts in fish contaminated with PAHs and exposed to NO(2)(-) in the ambient water. Electrospray ionization tandem mass spectrometric (ESI-MS/MS) analysis of the bile of the euryhaline fish Oreochromis mossambicus exposed simultaneously to field relevant sublethal concentrations of phenanthrene and NO(2)(-) and collision-induced dissociation of selected ions revealed the presence of DNA-PAH adducts. The present study indicates that, although several high sensitivity techniques have been developed for the analysis of PAH derived DNA adducts, MS/MS has emerged as a powerful tool in the detection and structure elucidation of DNA adducts. Juvenile O. mossambicus from a local estuarine fish farm were used with increasing frequency for carcinogenicity testing and comparative cancer research. The fish were exposed to the alkylating agent phenanthrene in the presence of NO(2)(-). Composite untreated bile samples after dilution with methanol: water (1:1; v/v) were analyzed by ESI-MS. Several adducts could be evidenced in the bile by MS/MS. Deoxyadenosine/deoxyguanosine having a mass in the range of 450-650 amu is detected. In addition, a segment of modified dinucleotide with a mass that corresponds to a dimer consisting of a modified guanosine and a normal guanosine has also been identified in the bile. The formation of certain types of DNA adducts is a crucial step in the induction of cancer and a primary stage in mutagenesis. Phenanthrene injected by i.p. route led to the transformation of phenanthrene to N-formyl amino phenanthrene-N(6)-deoxyadenosine adduct, whereas the fish co-exposed to phenanthrene and ambient nitrite metabolizes PAH to mono-, di- as well as trinitro derivatives, which then react with DNA leading to the formation of mainly modified guanosine and adenosine adducts. In the present investigation, dinitrophenanthrene diol epoxide (DNPDE) adduct with guanosine (m/z 587) seems to be the dominant adduct in the mixture, and its presence is shown first as a comparatively less stable adduct, which decomposes to give a more stable N(2) adduct (m/z 567). MS/MS has proved to be useful in the rapid determination and discrimination of structurally different phenanthrene/derivatives DNA adducts in a complex mixture of fish bile co-exposed to phenanthrene and nitrite. However, the nature of metabolites formed is likely determined by the route of PAH administration, and there is a need to further define the early biochemical events of carcinogenesis in these species. DNA adduct analysis in fish bile offers a promising approach to study the risk of potentiation of anthropogenic chemicals into genotoxic compounds in the presence of nitrite in the marine environment. We believe this is the first report on the formation of DNA-phenanthrene adducts on co-exposure of the fish to PAH and nitrite.

Diet of the Neotropic CormorantPhalacrocorax olivaceusat West Chubut, Patagonia, Argentina

Fil: Casaux, Ricardo Jorge. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Direccion Nacional del Antartico. Instituto Antartico Argentino; Argentina. Universidad Nacional de la Patagonia San Juan Bosco; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas; Argentina

Preliminary Morphometrics of Spleen and Kidney Macrophage Aggregates in Clinically Normal Blue Gourami Trichogaster trichopterus and Freshwater Angelfish Pterophyllum scalare

Macrophage aggregate (MA) morphometry and pigment composition are believed to be dependent on the species, age, and health status of the fish. The aim of this study was to characterize a "normal" morphometry baseline of spleen and kidney MAs in blue gourami Trichogaster trichopterus and freshwater angelfish Pterophyllum scalare. Three size-classes of clinically normal fish were analyzed. Blue gourami and freshwater angelfish were obtained from three local ornamental fish farms; for each size-class, 10 fish from each farm were analyzed. Hematoxylin- and eosin-stained tissue sections were analyzed by light microscopy at 100x magnification and an image analysis program. The percentage of tissue occupied by MAs, MA size, and MA number were calculated on three arbitrarily selected fields of view from each spleen and kidney. In clinically normal blue gourami, increases in the percentage of tissue occupied by MAs and in MA size were associated with an increase in fish size, but in clinically normal angelfish no correlation was observed. Furthermore, in angelfish, a high variability in MA morphometry was observed, even among fish from the same sample group. In both species, a significant difference in the value of the morphometric parameters was observed among farms. Because iridoviruses inhibit macrophage activity and (possibly) proliferation, MAs in 25 clinical cases of iridovirus-infected blue gourami were analyzed. Preliminary data indicate that in iridovirus-infected blue gourami, there is a decrease in MA size and MA number compared with those of healthy fish.

Characterization of Streptococcus iniae isolated from ornamental cyprinid fishes and development of challenge models

Streptococcus iniae was isolated from red-tail black shark(RTB shark) Epalzeorhynchos bicolor, and rainbow shark, E. erythrurus (fam: Cyprinidae), obtained from a local freshwater ornamental fish farm in Hillsborough county (FL). Darkening of the skin and lethargy were the first signs observed in infected sharks. Hemorrhages were observed on the ventral side of the body, on the head, and at the base of the pelvic and pectoral fins. Exophthalmia was observed in a low percentage of fish (∼ 10%). Moribund fish demonstrated the characteristic spinning, swimming pattern observed during streptococcal infections. Histological analysis revealed leukocyte infiltration in the intestinal area, spleen, posterior kidney, and brain. Necrosis and tissue degeneration were observed in the same organs in addition to degeneration of the renal tubules. Gram positive cocci were isolated from the cultures of brain and kidney tissues. Bacterial identification was obtained with the BIOLOG MicroLog3 version 4.00 System (Biolog, Inc., Hayward, California) and with standard microbiological tests. S. iniae-free RTB and rainbow sharks were used for developing a challenge model with the isolated bacteria strain. The experiments were conducted in two separate recirculating systems each with 25 tanks, 38 L volume per tank. In all experiments, the water in the system was maintained at 25 ± 1 °C. For each treatment, there were 3 replicate tanks, each stocked with 25 fish. Tanks were randomly assigned to treatment or control groups. Sharks were challenged by intracoelomic injection of S. iniae, and mortality was recorded for 14 days. Moribund fish showed classical signs of streptococcosis and S. iniae was isolated from moribund and dead fish. Differences in susceptibility to S. iniae were observed between the two species. An injection of 1.5 × 10 4 colony forming units (CFUs)/fish caused mortality close to 70% in RTB shark, and a higher mortality rate in rainbow shark. Mortalities ceased in 11–12 days after bacterial challenge in RTB shark, and in 3–4 days in rainbow shark. In this report, the pathology of S. iniae infections in two ornamental freshwater sharks and the development of a challenge model are described.

Studies on the biofiltration capacity of Gracilariopsis longissima: From microscale to macroscale

The potential of the red agarophyte Gracilariopsis longissima as biofilter for phosphate and ammonium in effluents outflowing intensive marine fish cultures was assessed at different scales. Previous studies showed that both laboratory (microscale level) and outdoor cultivation (mesoscale level) were feasible, with a maximum sustainable yield of 270 g fresh wt m − 2 day − 1 approximately, at a biomass higher than that predicted in a logistic model, a deviation attributable to an improvement of the culture conditions during the monitoring period. At a mesoscale level, a 34-h cycle suggested that the nitrification rate on the seaweed fronds showed diel fluctuations, with rates peaking early in the morning, when ammonium uptake rates were negligible. Mean nitrification rates were similar to ammonium uptake rates, suggesting that nitrifyers outcompete G. longissima for the use of ammonium; especially when mean biofiltering efficiencies were less than 15% during the 34-h period. G. longissima thrives naturally in different earthen ponds of a fish farm in Cádiz Bay Natural Park, Southern Spain, especially in the outflowing reservoir earthen ponds, where biomass reached values up to 278 g dry wt m − 2 during the spring. A field cultivation system for G. longissima (macroscale level) was designed to find the best scenario in terms of earthen pond, season or current conditions. The best cultivation method was the growth of vegetative cuttings on suspended braided nylon ropes. The highest growth rates (up to 6% day − 1 ) and biomass (up to 10 g fresh wt cm − 1 rope) were obtained in ponds receiving outflow waters, suggesting a nutrient effect. The net P production reached 24.9 μg P cm − 1 rope day −1 and was also higher on braided nylon suspended ropes placed at the outflowing reservoir earthen ponds. A similar result was found regarding net N production. However, in this case, mean production (≈ 170 μg N cm − 1 rope day − 1 ) was similar in the different earthen ponds and channels. The increase in P and N biomass suggested that G. longissima was biofiltering efficiently nutrient wastes from the fish farm. The results pointed out the high potential ability of G. longissima to biofilter waste waters from a fish farm, encouraging a large scale cultivation of this species. Future practices using this macroalgae may be implemented in local fish farms, resulting in both environmental and economic advantages.

FISHY REFLEX

Everyone knows that familiar wobbly feeling when you've bounced out of bed too fast. But with a slight thumping of your heart and a gentle squeezing of the veins in your legs, you've effortlessly got your blood back to where it is needed, and you're on your way. For a long time researchers assumed that this`baroreceptor reflex', which helps our bodies maintain a stable blood pressure, evolved so that terrestrial creatures like us could deal with gravity constantly dragging our blood into our boots. But now it looks like fish are in on the trick too. Erik Sandblom and Michael Axelsson of Göteborg University in Sweden have shown conclusively that rainbow trout also have a `baroreceptor reflex'(p. 821).Sandblom has always loved fish and is intrigued by the mechanisms that allow these creatures to keep their blood pressure stable. Fish circulatory systems differ from mammalian systems: their heart only has two chambers instead of four. Fish oxygenate their blood by directing it through their delicate gills before pumping it around the body. Trout don't usually have to cope with blood pooling in their tails – their blood is the same density as the water they swim in – but they still need to regulate blood flow to their organs.To find out how fish regulate their blood pressure, Sandblom and Axelsson needed to find a way to control blood flow in free-swimming fish. Studying a non-anaesthetised fish's intricate system of blood vessels is notoriously difficult, but Sandblom and Axelsson weren't put off. Sandblom popped down to the local fish farm, loaded up a shoal of rainbow trout and headed back to the lab. After months of intensive work, the team finally developed a method that enabled them to increase or decrease gill blood pressure. They were ready to test the trout's `baroreceptor reflex'.Placing a few trout in the spotlight, Sandblom put them through their paces. He first temporarily closed the ventral aorta that sends blood to the gills, and noticed that, within seconds, a reflex had kicked in and the trout's heart was thumping faster and its veins were constricting to compensate for the drop in blood pressure. The opposite happened when Sandblom blocked the dorsal aorta that takes blood away from the gills. The forced pressure increase in the gills caused the trout's heartbeat to gently decrease. Sandblom and Axelsson are convinced that this is truly a reflex response and that they have hit on what might be driving the trout's`baroreceptor reflex'. Using the drugs prazosin and atropine, they went a step further and showed that the distinct blood vessel and heart rate responses are controlled by different nervous control systems.Sandblom is pretty excited about his technique. `It's a neat tool that can be used for many different purposes' he enthuses. He now wants to see what happens to the veins when fish are a little low on oxygen. Sandblom suspects that since fish live in a gravity-free environment the `baroreceptor reflex'simply evolved to keep arterial blood pressure at a certain level, and not just to help us legged creatures defy gravity and saunter around on land.

Distributions of planktonic sea lice larvae Lepeophtheirus salmonis in the inter-tidal zone in Loch Torridon, Western Scotland in relation to salmon farm production cycles

This study examines the relative density of sea lice, Lepeophtheirus salmonis (Krøyer), larvae in the inter-tidal areas of Loch Torridon, a fjordic sea loch in Western Scotland and the site of several commercial salmon farms. Samples of planktonic sea lice were collected in each spring from 1999 to 2003 near the mouth of the River Shieldaig, where sea trout have been shown to congregate in the first few days after going to sea, and from 2001 to 2003 near the mouth of the River Balgy. No larval sea lice were found near the mouth of the River Shieldaig in spring 2000 or 2002, when gravid female sea lice were absent on local fish farms. The same finding was observed in 2002 at the mouth of the River Balgy. In springs of 1999, 2001 and 2003, peak densities of larval sea lice of 33, 94 and 143 m−3, respectively, were observed at the mouth of the river Shieldaig. At the mouth of the River Balgy, peak densities of 74 and 78 lice m−3 were observed in 2001 and 2003 respectively. At the time these samples were collected, the two local salmon farms were in the second year of their production cycle and gravid female sea lice were present. Samples of larval sea lice were also obtained year round, at approximately weekly intervals, from a 50-m transect at the mouth of the River Shieldaig, from March 2001 to June 2003, and compared with frequencies of gravid female sea lice on the two local salmon farms. High levels were found in the winter. No planktonic sea lice were found in this transect when gravid females were not present on the local fish farms.

The expression of gill Na, K-ATPase in milkfish, Chanos chanos, acclimated to seawater, brackish water and fresh water

Juvenile milkfish Chanos chanos (Forsskål, 1775) were transferred from a local fish farm to fresh water (FW; 0‰), brackish water (BW; 10‰, 20‰) and seawater (SW; 35‰) conditions in the laboratory and reared for at least two weeks. The blood and gill of the fish adapted to various salinities were analyzed to determine the osmoregulatory ability of this euryhaline species. No significant difference was found in plasma osmolality, sodium or chloride concentrations of milkfish adapted to various salinities. In FW, the fish exhibited the highest specific activity of Na, K-ATPase (NKA) in gills, while the SW group was found to have the lowest. Relative abundance of branchial NKA α-subunit revealed similar profiles. However, in contrary to other euryhaline teleosts, i.e. tilapia, salmon and eel, the naturally SW-dwelling milkfish expresses higher activity of NKA in BW and FW. Immunocytochemical staining has shown that most Na, K-ATPase immunoreactive (NKIR) cells in fish adapted to BW and SW were localized to the filaments with very few on the lamellae. Moreover, in FW-adapted milkfish, the number of NKIR cells found on the lamellae increased significantly. Such responses as elevated NKIR cell number and NKA activity are thought to improve the osmoregulatory capacity of the milkfish in hyposaline environments.

Trichodinid ciliates (Peritrichia: Trichodinidae) from the Bay of Kiel, with description of Trichodina claviformis sp. n.

Investigations on the epizoic fauna of Gadus morhua (L.), Platichthys flesus (L.) and Oncorhynchus mykiss (Walbaum) from the Kiel Fjord and Kiel Bight were carried out from September 1996 to March 1997. Smears from 120 G. morhua and 92 P. flesus caught using fish traps and trammel nets, and of 35 O. mykiss obtained from a local fish farm in the Kiel Fjord revealed the presence of three species of trichodinid ciliates, Trichodina claviformiis sp. n., Trichodina jadranica Haider, 1964 and Trichodina raabei Lom, 1962. The new species can be distinguished from other trichodinids by its large size in combination with the characteristically shaped adhesive disc containing denticles with club-like formed thorns. The thorns are directed anteriorly and not towards the centre of the adhesive disc. As the Kiel Bight and Kiel Fjord are new locality records for T. jadranica and T. raabei, morphological data are provided for both species. Trichodina claviformis is the first record of a peritrichous mobiline ciliate from Atlantic cod of the Baltic Sea. An identification key for 16 Trichodina species occurring on Baltic Sea fishes is provided based on the morphology of the adhesive disc and other well-established features. The occurrence of trichodinid ciliates on G. morhua and P. flesus in the Baltic Sea is discussed, especially considering the biology of the host and a possible host specificity of the species.

Evaluation of immunoglobulins produced in vitro by head-kidney leucocytes of sea bass Dicentrarchus labrax by immunoenzymatic assay

Fish, like other vertebrates, posses an e$cient immune system based on humoral and cellular reactions (Manning, 1994). An antibody response is mounted in fish after immunisation with acellular antigens (Joosten et al., 1997; Palm et al., 1998) and in response to vaccination (Boesen et al., 1997; Marsden & Secombes, 1997; Palm et al., 1998). The kinetics of production of antigen-specific immunoglobulins (Ig) in teleosts shows a primary and secondary humoral response (van Muiswinkel, 1995). The cells responsible for antibody production are plasma cells and B cells (Koumans-Van Diepen et al., 1994), and they have traditionally been enumerated by the plaque-forming assay (PFA) (Jerne & Nordin, 1963; Rijkers et al., 1980). In recent years, the evaluation of antibody-secreting cells has been conveniently achieved using the ELISPOT assay in fish (Boesen et al., 1997; Joosten et al., 1997; Bandin et al., 1997; Davidson et al., 1997), as well as in other vertebrates (Wu et al., 1998; Chen et al., 1995; Hogenesch et al., 1996; Yoo et al., 1998; Kim et al., 1999). This assay can also be used to study Ig synthesis in fish in response to environmental pollutants (Aaltonen et al., 1997), and in mammals has been adapted to detect individual cytokine-secreting cells (Vandermeide et al., 1995). The aim of the present work was to study the humoral immune response of the Mediterranean sea bass Dicentrarchus labrax by means of a simplified ELISPOT that would allow quantitative data on B cell activities in vitro (production of antigenspecific Ig) without manual counting of the read out at a microscope. Such an assay would allow manipulation of a large number of samples and reduce assay time. Sea bass were produced and reared in seawater aquaculture in a local fish farm (La rosa S.r.l., Orbetello, Italy). Eighteen month old animals, 298 76 g in weight, were used in all experiments. Prior to handling, fish were anaesthetised with 1 mg ml 1 of tricaine methanesulphonate (Sigma). Fish (n=6) were injected intraperitoneally (i.p.) with 250 l of 0·15 M NaCl, 2·7 mM KCI, 1·5 mM KH2PO4 and 8 mM Na2HPO4, pH 7·4 (PBS) containing 250 g of dinitrophenylated keyhole limpet haemocyanin (DNP-KLH, Sigma) emulsified with 100 l of Freund’s complete adjuvant (Serva, Heidelberg, Germany) (Findlay & Tatner, 1996). Alternatively, fish (n=4) were injected i.p. with 250 l fish 1 of PBS containing bacteria centrifuged from a 0·5 ml solution (ca. 2·5 10 cells) of Vibrio Anguillarum serotype 1 and serotype 2 vaccine (Microtek Europe, Brambles, U.K.) without adjuvant. Control fish (n=10) were injected i.p. with