Is the decline of birds and amphibians in a steppe lake of northern Patagonia a consequence of limnological changes following fish introduction?

• 1. Laguna Blanca, in Laguna Blanca National Park, is a lake in Patagonia which has been designated as a Ramsar site since 1971 because of bird diversity and abundance and importance for nesting, particularly for the black neck swan, Cygnus melanocoryphus. It is also valued for its populations of endemic amphibians, Atelognathus patagonicus and Atelognathus praebasalticus.
• 2. Avian and amphibian populations have decreased dramatically in recent years. Percichthys colhuapiensis, Percichthys trucha (Pisces, Percichthyidae), Salmo trutta and Oncorhynchus mykiss (Pisces, Salmonidae) were introduced into Laguna Blanca in 1965. Since 1986, no Atelognathus frogs have been found. The abundance of swans and coots, which are strongly associated with macrophytes for nesting and feeding, has diminished drastically, whereas piscivorous birds have increased.
• 3. The fishless condition of some neighbouring small lakes with abundant pond weeds, aquatic birds and endemic amphibians, was assessed in order to compare the physical and chemical characteristics and the quantitative composition of the benthos among lakes. Fish presence at Laguna Blanca and its absence at El Burro, Antiñir and Jabón lakes, were confirmed. Compared with previous results, it seems that the abundance of Amphipoda (Hyalella), Copepoda and Cladocera at Laguna Blanca has decreased, while Acari has increased and Notostraca has disappeared. Water transparency has diminished in Laguna Blanca and now is lower than that of fishless lakes.
• 4. P. colhuapiensis were captured only in Laguna Blanca, with the highest captures in the littoral zone. The population shows rapid individual growth in the early years and an absence of fish older than 6 years. The preponderance of benthos and the presence of macrophytes in the gut contents of adult P. colhuapiensis appear to indicate that they are important consumers of these resources.
• 5. This paper concludes that fish introduction in Laguna Blanca led to a complex trophic cascade effect (fish predation on tadpoles, fish competition for avian food, bottom disturbance, zooplankton reduction) producing deleterious effects on the amphibian and bird populations.

Copyright © 2006 John Wiley & Sons, Ltd.     

Viability of a Freshwater Mussel (Elliptio complanata) as a Biomechanical Filter for Aquaculture Ponds I: Clearance Rate of Chlorophyll-α

The production and livelihood of aquaculture facilities depend on increased growth of species being harvested. Only 15%-25% of nitrogen and phosphorus are retained in farmed fish even when all feed is consumed. In both marine and freshwater aquaculture systems, bivalves have proven to be an inexpensive method for controlling algal growth through suspension feeding. With 25% of the native U.S. freshwater mussel species under federal protection, their use in aquaculture ponds could lead to further propagation and restoration of natural populations. Elliptio complanata is an important species in Delaware rivers and connected estuaries; a recent two-year study by the United States Geological Survey found that 98% of mussels found in the Delaware River were Elliptio complanata. The objective of this study was to calculate the clearance rate of E. complanata in a laboratory study. This would help us determine if mussels can serve as an addition to chemical and mechanical filtration regiments and thrive in an aquaculture setting. Using feeding chambers we investigated the effect of E. complanata on algae grown from an aquaculture pond and on a cultured alga over a four-hour period. Temperature, dissolved oxygen, and pH were monitored, and samples were than analyzed for total chlorophyll-α. The average of both the single cell using Chlorella vulgaris and mixed assemblage treatments chlorophyll-α clearance rate was 0.187 liters per hour per mussel. Prior to this experiment, these mussels were held for a period for two months in the holding system in the laboratory. The resulting low clearance rate as compared to the previous studies in the field is possibly due to the stress from holding these mussels. However, our study demonstrated that mussels have the potential to be used in an aquaculture setting and/or recreational ponds to help reduce algae populations that can occur as a result of eutrophication.     

Start-up performance of a woodchip bioreactor operated end-of-pipe at a commercial fish farm—A case study

There is a need for simple, maintenance-free technologies for removing nitrogen (N) from aquaculture effluents. Denitrifying woodchip bioreactors have been used successfully to remove nitrate-N (NO₃-N) from ground and surface waters and may potentially be applied to dilute aquaculture effluents as well. Real-life applicability in commercial, outdoor fish farms including practical start-up issues such as e.g. time till stable performance and potential leaching are, however, unknown to the industry.This case study consequently investigated the temporal performance of a woodchip bioreactor (12.5 m³) during start-up. The bioreactor was operated end-of-pipe at a commercial, outdoor rainbow trout (Oncorhynchus mykiss) farm in Denmark operated at low recirculation intensity. Applying an empty bed contact time (EBCT) of 5 h, the specific objectives of the study were to resolve: i) how fast the bioreactor would start to remove NO₃-N; ii) how fast steady state was achieved; iii) which NO₃-N removal rates could be attained at the relatively low effluent temperature (∼8 °C) and iv) to which extent any concomitant leaching of phosphorous (P), ammonia or organic matter would occur.In- and outlet grab samples were obtained every 6 h until the bioreactor was in steady state (2 weeks) followed by weekly 24 h pooled samples for another 3 weeks (5 weeks in total). Additional grab samples were obtained from 9 sampling ports within the bioreactor on 3 consecutive days during steady state. Samples were analyzed for dissolved nutrients (total N, nitrate, nitrite, ammonium, total phosphorous, ortho-phosphorous, BOD₅ and COD). In addition, oxygen, temperature and pH were logged every 30 min while sampling and alkalinity were measured once a week.Removal of NO₃-N started immediately and remained stable at 7.06 ± 0.81 g NO₃-N/m³/d (n = 6) throughout the sampling period. Increased effluent NO₂-N concentrations (peaking at 1.14 mg NO₂-N/l after 4–5 days) were transiently observed during the initial 11 days. After that, the woodchip bioreactor was largely in steady state with respect to N-balances corroborated by a close match between filtered total-N (TN_diss) and NO₃-N removal rates. Measurements within the bed showed that the majority of the influent dissolved oxygen (DO) was consumed within the first part of the bioreactor and that NO₃-N removal thereafter proceeded gradually with distance within the bed. Leaching of non-structural, dissolved organic compounds were observed just after startup, causing a short-term (1 week) increase in effluent concentrations of COD, BOD₅, P and ammonium.Additional measurements carried out until 147 days after start-up showed that the woodchip bioreactor continued to remove TN_diss at an average removal rate of 7.81 ± 0.82 g N/m³/d, and that the initial leakage of P stopped altogether.In summary, the study demonstrated that woodchip bioreactors can effectively remove NO₃-N from dilute aquacultural effluents at low temperatures and commercial conditions and that stable performance is achieved within a few weeks.     

Short-Term Dinoflagellate Bloom in a Shrimp Pond in Bahía de La Paz,Gulf of California

From mid-August to mid-September 1998, a dinoflagellate bloom in a shrimp pond near La Paz, Baja California Sur, was studied. Daily samples were taken of phytoplankton, dissolved oxygen, nutrient concentrations, photosynthetic pigments and proteins. The bloom occurred at temperatures of 29.7 to 33.2?°C. High densities of a Scrippsiella-like dinoflagellate (15.9?×?10⁶ cells/L) occurred on the first day of sampling, reaching a peak of 249?×?10⁶ cells/L on Day 13, and declining to 4 to 7?×?10⁶ cells/L by Day 26. Chlorophyll a varied from 8.63 mg/m³ on Day 4 to 141.38 mg/m³ on Day 13. Total nitrogen varied widely (0.2–11.50 μM) while phosphates peaked only once on Day 13 (4.14 μM). Proteins ranged from 523 to 6387 μg/L; the latter value occurred two days after the maximal peak of nitrates and coinciding with the highest level of phosphates. Fertilizers added to the ponds increased nutrient concentration and stimulated phytoplankton growth. In turn, the food supply to cultured shrimp noticeably increased throughout the bloom.     

Potent activation of tumor necrosis factor-α production by a polysaccharide found in a marine brown alga Chordaria flagelliformis

In a search for new antitumor drugs, we collected 334 species of marine algae from the Japanese coastline and screened these for tumor necrosis factor-alpha (TNF-α) production-promoting activity in an in vitro assay with the mouse macrophage-derived cell line RAW264.7. A phosphate-buffered saline extract from the marine brown alga Chordaria flagelliformis was found to strongly promote TNF-α activity. Further purification of this alga by precipitation with ethanol and two-step chromatography yielded an approximately 3,000-kDa polysaccharide as the active substance, which we designated MC25. MC25 exhibited TNF-α production-promoting activity in RAW264.7 cells in a dose-dependent manner, and we established its temperature and pH stabilities and non-cytotoxic character. Its molecular structure is similar to that of a fucoidan in terms of composition, including glucose, fucose, xylose, and uronic acid. The molecule hydrolyzed to a size of 180–370 kDa still retained strong TNF-α production-promoting activity, suggesting that MC25 might be a promising candidate in the development of novel antitumor agents.     

Towards interactive fish farming governance? a comparison of Finland and Sweden

The neighbouring countries, Finland and Sweden, compete in the same market with their aquaculture. Both countries have had, until recently, stringent environmental policies limiting production volumes. During recent years, however, Swedish fish farmers have been able to increase their production volume, and Finnish fish farmers have also redirected their investments to Sweden. Thus, the strict Finnish environmental permit policy has not benefited the Baltic Sea environment, but has moved the production volumes and employment opportunities to other locations in the Baltic Sea and its drainage basin. By comparing the Finnish and Swedish fish farming governance systems, we found that in Sweden, various types of formal and informal interaction and practice have enhanced the achievement of balanced decisions. This has only rarely been the case in Finland, which features a more authoritative decision-making culture. On the other hand, increased communication across the Finnish administrative sectors raises future prospects for more holistic fish farming governance, which balances economic, social and environmental goals.     

Are River Styles ecologically meaningful? A test of the ecological significance of a geomorphic river characterization scheme

• 1. Classification is a useful tool for researchers and managers wishing to group functionally similar sites or to identify unique or threatened habitats. A process‐based river classification scheme that successfully integrates physical and biological aspects of lotic form and function would enhance conservation and restoration efforts by allowing more meaningful comparisons among sites, and improving functional understanding of lotic ecosystems.
• 2. The River Styles framework provides a geomorphological river characterization scheme in which assemblages of geomorphic units vary for differing River Styles, presenting differing arrays of aquatic habitat diversity for each style.
• 3. The ecological significance of the River Styles framework is tested by comparing the macroinvertebrate assemblages and habitat characteristics of pool and run geomorphic units for three different River Styles on the north coast of New South Wales, Australia.
• 4. Multivariate ordinations and analysis of similarity (ANOSIM) revealed that macroinvertebrate community structure differed between Bedrock‐Controlled Discontinuous Floodplain rivers and Gorge rivers, and between Bedrock‐Controlled Discontinuous Floodplain and Meandering Gravel Bed rivers, especially in pools. Differences between Gorge and Meandering Gravel Bed rivers were less apparent, largely due to variations within the Meandering Gravel Bed rivers group.
• 5. The variability in macroinvertebrate assemblage structure among geomorphic units was most strongly related to variability in substrate and hydraulic variables. Substrate composition differed significantly among all River Styles and geomorphic units, but other habitat variables showed few consistent differences among River Style groups.
• 6. These results suggest that the ecological similarity of macroinvertebrate communities within River Styles may presently be limited because some important large‐scale drivers of local habitat conditions are not included in River Styles designations. Integrating River Styles classification with other large‐scale variables reflecting stream size, temperature and hydrological regime may produce a process‐based physical classification capable of identifying river reaches with similar ecological structure and function.

Copyright © 2003 John Wiley & Sons, Ltd.     

SHADYS (‘simulateur halieutique de dynamiques spatiales’), a GIS based numerical model of fisheries. Example application: The study of a marine protected area

This paper presents the simulator SHADYS (‘simulateur halieutique de dynamiques spatiales’). SHADYS is a tool devoted to the representation of spatial processes involved in fisheries dynamics. It puts together three fundamental entities in an explicit spatio-temporal way: the environment, the fish populations under consideration and the fishing fleet. It is based on simple, realistic and well identified mechanisms (density-dependent habitat selection, advection and diffusion of a fish population, fishermen search strategy, etc.) implemented by interfacing numerical models with a GIS (geographic information system). As a virtual laboratory, SHADYS allows experiments to be performed in a theoretical world, such experiments being generally impossible to perform in reality. As an illustration, different scenarios of a marine refugia-based management have been explored using the SHADYS simulator. Different simulations are conducted to assess the short-term effects on yield of a marine protected area. It is shown that for diffusive or migrator) species, the yield per recruit as a function of the protected surface can reach a maximum. Under this condition, the concept of ‘space overfishing’ is meaningful. Protected areas then behave like ‘sources’ and exploited areas like ‘sinks’. For resident populations, the larger the protected area is, the lower the catches per recruit are. Regarding the spatial distribution of the fishing effort, it is shown that if it is spatially distributed in order to maximize catches, then fishing boats will slowly tend to be distributed all along the boundaries of the protected area.     

Can Different Body Tissues of Two Sea Cucumbers Supply a Fair Amount of Omega 3 for Health Benefit?

The lipid content and fatty acids profile of different tissues of Holothuria tubulosa and H. polii were analyzed to assess the suitability of the central Mediterranean species as a potential marine resource for fatty acids, in particular omega-3 polyunsaturated fatty acids (n-3 PUFAs). Simultaneously, their important indices for human health were evaluated. Gonad and respiratory tree had the highest lipid content, while the body had the lowest values. The results showed significant differences between species and among the different portions analyzed. Internal tunic and longitudinal muscle of H. tubulosa exhibited the highest PUFA proportion (55.3 and 46.4%, respectively). Eicosapentaenoic acid (EPA, C20:5n-3) and arachidonic acid (ARA, C20:4n-6) were the most abundant PUFAs in both species, with a favorable n-3/n-6 ratio in all tissues. The atherogenic and thrombogenicity indices and hypocholesterolaemic/hypercholesterolaemic fatty acid ratio suggested the high-quality of this food, similar to the nutritional values of most popular fish.     

The teleost pseudobranch: a role for preconditioning of ocular blood supply?

The physiological relevance of the teleost pseudobranch as a remnant of a reduced gill arch is still unclear. Numerous hypotheses have been proposed regarding its physiological role, but direct confirmatory evidence is lacking. The close relationship by serial blood flow arrangement with the fish eye’s choroid rete has sparked the idea that pseudobranchial preconditioning of blood pH may facilitate initiation of the Root effect and thus support the establishment of high oxygen tensions for retinal diffusive supply. This idea was critically tested by studies on isolated pseudobranchs in situ (Oncorhynchus mykiss), perfused with RBC/Ringer or RBC/plasma suspensions of widely varied composition (pH 7.4–8.2). Detailed analysis of inflowing as compared to effluent perfusates indicated normal aerobic metabolism expressed by a rise in Pco₂ (+0.39 ± 0.13 mmHg ), an oxygen utilization of 25% and a high oxygen consumption of ∼400 nmol g⁻¹ min⁻¹. Upon passage of the pseudobranch, pH (corrected for Haldane effect) was only slightly acidified (−0.03 to −0.10), [HCO₃ ⁻] and [lactate] were slightly enhanced (+0.51 mmol l⁻¹ or 0.13 mmol l⁻¹, respectively). In order to test for yet unknown plasma components involved in pseudobranch function, a second series of experiments was conducted using RBC-suspensions in fresh plasma instead of Ringer, with results closely resembling those of the RBC/Ringer series. Lacking any physiologically significant correlation with the level of perfusate pH, the obtained data indicate pseudobranchial basic metabolic activity rather than pH regulatory characteristics. Also the observed absolute changes in pH are negligible in terms of pH regulation towards the Root-threshold. Accordingly, the present experiments as well as plausibility evaluation of mechanisms do not support the idea of blood pH pre-adjustment prior to entry into the choroid rete structure of the teleost eye to facilitate the Root-mediated oxygen release.     

Can the presence of a large conspecific improve the production and welfare of groups of smaller self‐feeder competent rainbow trout?

This study examined the production and welfare effects of including a large self‐feeder competent rainbow trout, Oncorhynchus mykiss (Walbaum) (~665 g) in groups of smaller self‐feeder competent conspecifics (~234 g). Costs and benefits were examined for both welfare (aggression, fin damage, condition and mortality) and production (self‐feeder utilization and growth). The 8‐week experiment used six groups of small trout; three treatment groups containing a large trout and three control groups. After 4 weeks the large fish were removed from treatment groups and added to control groups, thus reversing the treatments. Whilst it was thought that the presence of a larger fish would suppress aggression in smaller conspecifics this did not occur. In fact aggression was significantly (P = 0.036) higher when large trout were present during the first 4 weeks. No significant differences were found between other welfare indicators, self‐feeder utilization or production parameters. From a production and welfare perspective these results suggest that with the exception of initially increasing aggression larger fish do not represent a significant benefit or risk to smaller conspecifics being cultured in self‐feeder equipped tanks, when all fish are self‐feeder competent.     

Existence of a 400 kDa glycoprotein in the dermis of sea cucumber Apostichopus armata: partial purification and characterization

A large size (400 kDa) non-collagenous protein was detected as a major component in the extract, with neutral salt solution, from the dermis of sea cucumber Apostichopus armata. On SDS-PAGE analysis, the 400 K component shifted to a lower molecular weight component (about 200 K) by reduction with 2-mercaptoethanol, and they were both reactive for periodic acid-Schiff (PAS) reaction staining. From these results, this protein was suggested to be a glycoprotein consisting of disulfide-bonded two subunits with almost equal molecular weight (200 K). In addition to relatively high contents (>100/1,000 residues) of aspartic and glutamic acids, cysteine was also detected (6.1/1,000 residues) in amino acid analyses of this protein partially purified by anion-exchange column chromatography. These combined results suggest the structural similarity of the 400 K component to fibronectins from other vertebrate and invertebrate animals.     

Optimization of fish to mussel stocking ratio: Development of a state-of-art pearl production mode through fish–mussel integration

Integrated aquaculture has been widely used for pearl production in the freshwater pearl mussel Hyriopsis cumingii farming in China, but the production technology has not reached the state of the art. This study explored the optimal stocking ratio of fish to mussel (fish–mussel) through a 90-day experiment conducted in land-based enclosures. The integrated system included pearl mussel, grass carp, gibel carp, silver carp and bighead carp, with four fish–mussel stocking ratios by number: 1:1 (R1), 2:1 (R2), 3:1 (R3) and 4:1 (R4). The pearl yield was higher in the R2 enclosures than in the R1 and R4 enclosures, whereas the fish yield was higher in the R3 and R4 enclosures than in the R1 and R2 enclosures. The phosphorus (P) utilization efficiency was higher in the R2, R3 and R4 enclosures than in the R1 enclosures. The wastes of nitrogen (N) and P enhanced with the increase of fish–mussel ratio. Regression analyses indicated that the fish–mussel ratio was 2.3:1 for the maximal pearl yield, and 3.6:1 for the maximal fish yield, and 1.6–2.3:1 for the minimal N waste, and 1.9–2.9:1 for the minimal P waste. This study indicated that the suitable fish–mussel stocking ratio was 2:1 in the integrated culture of H. cumingii, grass carp, gibel carp, silver carp and bighead carp.     

Technical efficiency of carp pond culture in South Asia: An application of a stochastic meta‐production frontier model

Abstract

A stochastic meta‐production frontier model is estimated to examine the inter‐country differences in levels of technical efficiency of semi‐intensive/intensive and extensive carp pond culture systems among the major carp producing countries in South Asia, namely India, Bangladesh, Pakistan, and Nepal. The mean technical efficiencies for semi‐intensive/intensive farms vary from 0.68 for Nepal to 0.79 for India, with an overall average of 0.75 and those for extensive farms vary from 0.48 for Bangladesh to 0.62 for Pakistan, with an overall mean of 0.57. Differences in efficiency levels are explained in terms of various farm‐specific and country‐specific factors by estimating a model for technical inefficiency effects. The adoption of recommended fish, water, and feed management practices is found to be critical for improved performance of carp producers. For each country, the study also compares the efficiency scores based on its own production frontier with those obtained from the meta‐production frontier.     

The value of recreational fishing in Sweden – Estimates based on a nationwide survey

A nationwide recreational fishing survey in Sweden was used to estimate the benefits of recreational fishing in Sweden. The survey targeted the Swedish population and, consequently, the sample contained a large fraction of zero fishing days. To consider this, a zero-inflated Poisson model was used in the estimations. Swedes fished about 15.6 million days in 2013, of which two-thirds were spent on inland fishing, and one-third on marine and coastal fishing. Expected consumer surplus per fishing day varied with the season; SEK 193 for winter fishing, SEK 787 for summer fishing and SEK 95 for autumn fishing. Although about 70 per cent of total fishing days were spent on inland fishing, the weighted consumer surplus per fishing day in marine and coastal areas were higher. The results also demonstrated strong positive effects of increases in expected catch per day on number of fishing days demanded and consumer surplus, which have important implications for fishery policies directed at recreational fishing.     

Is the crown-of-thorns starfish a threat to the reefs of Lord Howe Island?

• 1 Lord Howe Island, a World Heritage Area which lies in the southern Pacific Ocean, has the most southern true coral reefs in the world.
• 2 In the past decade, populations of Acanthaster planci, the crown-of-thorns starfish, have significantly reduced coral cover at Elizabeth and Middleton Reefs, approximately 200 km to the north of Lord Howe Island, and a small population has been reported from Lord Howe Island.
• 3 The abundance and distribution of A. planci was evaluated using surveys by the local recreational diving industry and video-transects, and the potential rate of recovery of the coral community following predation was assessed by analysing coral recruitment patterns.
• 4 The starfish population at Lord Howe Island remained relatively small and localized between 1984 and 1993.
• 5 Coral recruitment was dominated by the juveniles of brooding corals, and these same species dominated the established coral community. There was limited recruitment of broadcast-spawning coral species during the study period, suggesting that southern dispersal of coral larvae from more northern sites may be a rare or sporadic event.
• 6 The results indicate that there is only a small probability that the present starfish population will result in a major starfish outbreak. However, the recovery of the coral community from a major outbreak would be slow because of the apparently low rate of input of coral larvae from sources external to the reef.
• 7 Management agencies need to consider whether the present small and localized starfish population should be removed, given the likely ramifications of an infestation and the economic importance of the reef to tourism.

     

Molecular and phenotypic characterization of Vibrio aestuarianus, a pathogen of the cultured tongue sole, Cynoglossus semilaevis Günther

Studies were conducted to determine the cause of high mortalities of cultured half-smooth tongue sole Cynoglossus semilaevis. Gross signs of disease included loss of appetite, erratic swimming, and haemorrhages on the head, opercula and base of fins, dorsal fin rot, swollen abdomen filled with ascitic fluid and herniation of the intestine. Histological examination of the liver showed focal areas of necrosis and extensive haemorrhages. Virtually pure, dense bacterial cultures were obtained from liver, kidney and spleen tissues, and high pathogenicity of the isolates to tongue sole was confirmed. The phenotypic characteristics of the isolates including morphological, physiological and biochemical characteristics were determined. The 16S rRNA and gyrB genes of the isolates were sequenced, and the phylogenetic trees representing genetic relatedness between the isolate and publicly available 16S rRNA and gyrB gene sequences from GenBank were constructed. The results confirmed that the diseased tongue soles were infected with Vibrio aestuarianus. The sequenced 16S rRNA gene of strain TS1 (GenBank Accession No. GQ372983) was 1446bp, the gyrB gene of strain TS1 (GenBank Accession No. GQ372984) was 1200bp and the two genes exhibited high similarity (98~99%) to those of V. aestuarianus from GenBank. In addition, the activities of extracellular enzymes and haemolysin were also studied; the results showed that the isolates produced beta haemolysis on rabbit blood agar, lecithinase, proteinase, DNase and lipase, but gelatinase was not produced.     

Effects of feeding (ω-3) HUFA-enriched Artemia during a progressively increasing period on the larviculture of freshwater prawns

Larvae of the freshwater prawn (Macrobrachium rosenbergii) were reared to post-larvae in a closed recirculation system. Six treatments were designed where freshly-hatched Artemia nauplii were first given to the larvae for 3, 7, 11, 15, 17 and 25 days according to the treatment. After that (-3) HUFA-enriched Artemia were given until the 28th day at which time the test was terminated and evaluated. The requirement for (-3) Highly Unsaturated Fatty Acids (HUFA) for the larval stages of M. rosenbergii was confirmed by this experiment. Moreover, the longer the period of feeding on (-3) HUFA-enriched Artemia nauplii, the better the results in terms of growth, metamorphosis rate, survival and stress resistance.