Distribution patterns of settlement-stage juveniles of <Emphasis Type="Italic">Girella punctata</Emphasis> and <Emphasis Type="Italic">Girella leonina</Emphasis> on the rocky coast of the Kanto–Izu region,Japan

The early life history of girellid fishes in Japanese waters is unclear, and little is known about their species-specific reproductive strategies. We examined seasonal changes of distribution patterns for settlement-stage juveniles of Girella punctata and Girella leonina on the rocky shore in the regions of Kanto and Izu, Japan, to infer the influence of the Kuroshio Current on their reproduction. We collected 813 settlement-stage juveniles mainly in Sagami Bay and genetically identified the species. The juveniles of G. punctata were collected on the rocky shore in Sagami Bay during April to August, with the abundant catch in May and June. Thus, we infer that juvenile G. punctata ubiquitously inhabit the rocky shore in the area in spring and summer. By contrast, juveniles of G. leonina were rarely collected in Sagami Bay, with a total catch of only 66. Notably, no juveniles were collected during the wintertime in Sagami Bay, although an abundant catch of G. leonina had been previously reported for Sagami Nada off Sagami Bay during January to March. This clear-cut difference between the areas likely reflects the difference in proximity to the path of the Kuroshio Current. We expect that the Kuroshio Current strongly influences the reproductive success of G. leonina.     

The presence and expression of the HIF-1α in the respiratory intestine of the bronze Corydoras <Emphasis Type="Italic">Corydoras aeneus</Emphasis> (Callichthyidae Teleostei)

Bronze corydoras (Corydoras aeneus) is a small diurnal activity fish from South America. Under hypoxia conditions, it uses the posterior part of the intestine as an accessory respiratory organ. The present PCR studies demonstrated higher expression of HIF-1α (hypoxia-inducible factor) gene in the respiratory than that in digestive part of bronze corydoras intestine. Further, immunolocalization studies using antibodies specific to HIF-1α and transmission electron microscopy (TEM) revealed the presence of HIF-1α epitopes in the intestine of Corydoras aeneus. In the respiratory intestine, the numerous clusters of gold particles visualizing HIF-1α antibody were observed within fibroblasts, whereas in the digestive tract of this species, single gold grains in the epithelial cells were noted. On the other hand, the presence of HIF-1α and the cytoplasmic domain of the epidermal growth factor receptor (EGFR) in the respiratory intestine of bronze corydoras assumes their interactions in the system where these factors appeared for the first time. The non-obligatory air-breathing fishes using their digestive tract as an accessory respiratory organ during hypoxia conditions are very interesting for the studies of the processes that control HIF-1α expression and squamous cell proliferation.     

The “tsunami break:” impact of the Great East Japan Earthquake and the accompanying tsunamis on the shell growth of the invasive clam-eating snail <Emphasis Type="Italic">Laguncula pulchella</Emphasis>

The Great East Japan Earthquake and accompanying tsunamis occurred on 11 March 2011, causing huge damage to marine organisms. The invasive naticid gastropod Laguncula pulchella (Euspira fortunei), which was introduced with the imported clam Ruditapes philippinarum from China and Korea, survived the earthquake. The “growth break line” observed on the shell surface in over 90% of the individuals collected in Matsushima Bay and Matsukawa-ura Lagoon after the tsunamis was examined by scanning electron microscopy. Each shell presented three layers before and three after the growth break. However, the fracture surface consisted of five layers—two prismatic and three crossed lamellar—around the growth break line. This suggests that shell formation temporarily ceased following the tsunamis and that the five-layered shell may have developed in response to the stress caused by the tsunamis. The newly formed middle layer became thinner after the “tsunami break,” which may be the result of a rapid change in the mineralization process, including rapid shell growth and/or repair. These results suggest that the damage to and forcible removal of habitats by the tsunamis was stressful for L. pulchella. A decrease in or the cessation of shell formation after a tsunami may be a common phenomenon in mollusks that inhabit tidal flats.     

Can we increase haddock yield within the constraints of the Magnuson–Stevens Act?

Georges Bank haddock is a recently recovered fish stock in the New England groundfish fishery. Due to federal constraints under the Magnuson–Steven Act, however, this stock cannot be optimally exploited due to the bycatch of other critical species in the New England groundfishery such as cod and yellowtail flounder which are overfished. The Ruhle trawl and Separator trawl are examples of recent advances in gear technology that have been shown to significantly increase haddock to bycatch ratios. This study models the groundfish fishery through a mixed-stock yield model which incorporates technological interactions. We also develop a socio-economic model that quantifies the amount of employment and producer surplus associated with three trawl types. Our results explore policy situations regarding the use of the new trawls. By bridging the biological and socio-economic models, we are able to view the fishery as a system that more accurately represents stakeholder views. Our model shows that each trawl, when used exclusively, produces different optimum strategies and therefore an optimum management strategy would most likely include a combination of trawl types. Our results also support the logic of using modified trawls for haddock fishing trips in which bycatch is strictly regulated (“B days”) as the Ruhle trawl is able to maintain 80% of catches caught by a conventional trawl while reducing bycatch up to over 60%. This paper is a first step towards an aid for policy makers to examine fishery gear trade-offs and the resulting biological and socio-economic consequences of different management actions within the constraints of the Magnuson–Stevens Act.     

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.     

Use of biomarkers to assess the welfare of the edible clam, <Emphasis Type="Italic">Ruditapes philippinarum</Emphasis>: may it be a tool for proving areas of origin?

The use of biomarkers as early-warning signals to assess the impact of pollutants and other environmental stressors in coastal habitats has been internationally recognized as a useful tool in marine coastal monitoring. We propose a similar approach to verify the welfare of edible shellfish, Ruditapes philippinarum, thus exploiting its possible application as an effective tool to verify the origin of fishing/aquaculture products. A selected battery of biomarkers was chosen and applied to organisms from two different habitats in the Lagoon of Venice (a farming site and a natural area where fishing is currently banned, because of pollution problems) and from a local market. Biological responses were evaluated physiologically (survival in air test and condition index), behaviourally (reburrowing rate), and histochemically (quantification of neutral lipids and lipofuscin). Micropollutants (heavy metals, PCBs, and PAHs) were also determined in the soft tissues. Results indicated clams from the farming site were in the best condition with regard to both chemical and biological measurements. In contrast, the market sample contained the highest concentrations of PAHs. PCBs and heavy metals varied slightly and quite irregularly among the three samples. The worst values of the biomarkers were observed for clams collected at the polluted site, where, in particular, the lowest physiological and behavioural indexes and the highest accumulation of lipofuscin in the digestive tissue were recorded.     

Effects of dietary riboflavin levels on antioxidant defense of the juvenile grouper <Emphasis Type="Italic">Epinephelus coioides</Emphasis>

This study was conducted to evaluate the effects of dietary riboflavin on antioxidant defense in the juvenile grouper Epinephelus coioides. Graded levels of riboflavin (0.9, 1.6, 4.4, 6.7, 12.9 and 19.4 mg kg⁻¹ dry diet) were fed to grouper juveniles (mean weight: 14.90 ± 0.46 g) for 12 weeks. Higher levels of liver thiobarbituric acid reactive substances (TBARS) content were observed in grouper fed low doses (0.9 and 1.6 mg kg⁻¹ diet) of riboflavin. Both liver glutathione reductase (GR) activity and its activation coefficient (GR-AC) poorly responded to riboflavin deficiency. In addition, other indices of the glutathione-dependent defense system, including the activities of glutathione peroxidase (GSH-PX) and glutathione-S-transferase (GST), and the content of glutathione (GSH), were also non-significantly affected by dietary riboflavin levels. However, the activities of liver superoxide dismutase (SOD) and catalase (CAT) were significantly lower in fish fed 0.9 mg kg⁻¹ diet, with a positive correlation between the different groups. In conclusion, the present study indicated that the juvenile grouper fed the riboflavin-unsupplemented diet was susceptible to lipid peroxidation (LPO), with lower SOD and CAT activities in the liver. However, the glutathione-dependent defense system of grouper was not affected by dietary riboflavin levels.     

Determination of poly-β-hydroxybutyrate production by <Emphasis Type="Italic">Bacillus</Emphasis> spp. isolated from the intestines of various fishes

In this study, 30 strains of the genus Bacillus were isolated from various fresh fishes obtained from fish markets in Ankara, Turkey. They were identified as Bacillus pasteurii, Bacillus badius, Bacillus circulans, Bacillus licheniformis, Bacillus megaterium, Bacillus thuringiensis, Bacillus brevis, Bacillus cereus, Bacillus sphaericus, Bacillus subtilis, Bacillus coagulans, Bacillus lentus, and Bacillus pumilus. When poly-β-hydroxybutyrate (PHB) production by these strains was determined by spectrophotometry, it was found that PHB production ranged from 0.81–23.38% (w/v). PHB production and productivity were highest for B. pasteurii P2 (20.58% w/v) and B. lentus P18 (23.38% w/v). Furthermore, B. pasteurii P2 and B. lentus P18 were examined for PHB production using different carbon and nitrogen sources and in combined medium containing both carbon and nitrogen sources. The amounts of PHB produced by the strains in these media were more different than the amounts of PHB produced in nutrient broth medium.     

Do active‐dispersing insects dominate the invertebrate fauna of rock pools in the wet–dry tropics,Kimberley, Australia?

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Seasonal dynamics and yearly change in the abundance of metacercariae of <Emphasis Type="Italic">Parabucephalopsis parasiluri</Emphasis> (Trematoda: Bucephalidae) in the second intermediate host in the Uji–Yodo River,central Japan

An introduced pathogenic fish trematode, Parabucephalopsis parasiluri Wang, 1985 (Digenea: Bucephalidae), was studied to determine the seasonal fluctuation in its metacercariae abundance. The timing of the recruitment period of the metacercariae and the relationship between yearly fluctuation in metacercarial abundance and some environmental factors were also examined to develop an effective plan for disease control. Monthly changes in metacercarial abundance in the caudal fin of pale chub (Zacco platypus) and of the prevalence of the first intermediate host (golden mussel Limnoperna fortunei) suggest that P. parasiluri generally has an annual life cycle. The metacercarial abundance in chub increased when the water temperature fell below 7°C in winter, but the rapidity of the increase varied between 2007 and 2008. The fluctuations in the abundance of metacercariae in winter from 2001 to 2008 showed that mean flow rate and mean water level in January were negatively related to the infection level each year, and positively related to the mean water temperature. Based on these results, we propose a control plan for parabucephalopsiosis involving discharge control; that is, more than 50 m³/s (corresponding to 150 m³/s in the Yodo River) of water should be flushed from upstream dams for a period of at least one week starting on the day when the water temperature falls below 7°C.     

Effect of dietary components on the gut microbiota of aquatic animals. A never‐ending story?

It is well known that healthy gut microbiota is essential to promote host health and well‐being. The intestinal microbiota of endothermic animals as well as fish are classified as autochthonous or indigenous, when they are able to colonize the host's epithelial surface or are associated with the microvilli, or as allochthonous or transient (associated with digesta or are present in the lumen). Furthermore, the gut microbiota of aquatic animals is more fluidic than that of terrestrial vertebrates and is highly sensitive to dietary changes. In fish, it is demonstrated that [a] dietary form (live feeds or pelleted diets), [b] dietary lipid (lipid levels, lipid sources and polyunsaturated fatty acids), [c] protein sources (soybean meal, krill meal and other meal products), [d] functional glycomic ingredients (chitin and cellulose), [e] nutraceuticals (probiotics, prebiotics, synbiotics and immunostimulants), [f] antibiotics, [g] dietary iron and [h] chromic oxide affect the gut microbiota. Furthermore, some information is available on bacterial colonization of the gut enterocyte surface as a result of dietary manipulation which indicates that changes in indigenous microbial populations may have repercussion on secondary host–microbe interactions. The effect of dietary components on the gut microbiota is important to investigate, as the gastrointestinal tract has been suggested as one of the major routes of infection in fish. Possible interactions between dietary components and the protective microbiota colonizing the digestive tract are discussed.     

Estimation of the spawning grounds of chub mackerel <Emphasis Type="Italic">Scomber japonicus</Emphasis> and spotted mackerel <Emphasis Type="Italic">Scomber australasicus</Emphasis> in the East China Sea based on catch statistics and biometric data

The spawning grounds of the chub mackerel (Scomber japonicus) and spotted mackerel (Scomber australasicus) in the East China Sea were estimated based on catch statistics of the Japanese large- and medium-type purse seine fishery from 1992 to 2006. Biometric data were obtained from specimens caught by purse seiners in the East China Sea from 1998 to 2006. Gonadosomatic index (GSI) at 50% sexual maturity of chub mackerel and spotted mackerel females was 2.5 and 2.6, respectively. Using this criterion for GSI, chub mackerel larger than 275 mm and spotted mackerel larger than 310 mm in fork length were considered to be mature. Mature chub mackerel was observed in the area of 15–22°C sea surface temperature (SST), and mature spotted mackerel was observed in the area of 17–25°C SST. The spawning period of chub mackerel ranged from February to June, and that of spotted mackerel ranged from February to May in the East China Sea. The spawning grounds were estimated from the distributions of catch per unit effort (CPUE) of spawners and SST. As a result, the spawning ground of chub mackerel was estimated to be in the central and southern part of the East China Sea and the area west of Kyushu in February, March, and April, and in the central part of the East China Sea, the area west of Kyushu and Tsushima Straight in May, and in Tsushima Straight and western part of the Sea of Japan in June. The spawning ground of spotted mackerel was estimated to be in the central and southern part of the East China Sea and southern coastal area of Kyushu in February, March, and April, and the central and southern part of the East China Sea and the area west of Kyushu in May.     

Effects of light and temperature conditions on the expression of GnRH and GtH genes and levels of plasma steroids in <Emphasis Type="Italic">Odontesthes bonariensis</Emphasis> females

In this study we examined the endocrine mediation between environmental factors (temperature and photoperiod) and the brain–pituitary–gonadal axis in females of pejerrey Odontesthes bonariensis. Changes in the expression of brain gonadotropin-releasing hormones (GnRHs) and gonadotropin (GtH) subunit [follicle stimulating-β (FSH-β), luteinizing hormone-β (LH-β), glycoprotein hormone-α (GPH-α)] genes, plasma gonadal steroids [estradiol (E₂) and testosterone (T)], gonadal histology, and gonadosomatic index (GSI) in adult females exposed to combinations of short-day (8 h) or long-day (16 h) photoperiods and low (12°C) or high (20°C) temperatures after winter conditions (8 h light, 12°C) were analyzed. Pejerrey females kept under the short photoperiod had low GSIs, and their ovaries contained only previtellogenic oocytes regardless of the experimental temperature. In contrast, females exposed to the long photoperiod had high GSIs and ovaries with vitellogenic oocytes at both temperatures. These fish also showed a significantly higher expression of sGnRH, pjGnRH, cGnRH-II (the three different GnRH variants found to date in the pejerrey brain), FSH-β, LH-β and GPH-α genes and plasma E₂ levels than those at the shorter photoperiod. No significant changes were observed in plasma T levels. Based on these results, we concluded that the increase in day length but not that of temperature triggers the maturation of pejerrey females after the winter period of gonadal rest and that this occurs by an integrated stimulation of the various components of the brain–pituitary–gonad axis.     

Are hatchery‐reared abalone naïve of predators? Comparing the behaviours of wild and hatchery‐reared northern abalone,Haliotis kamtschatkana (Jonas, 1845)

Abalone populations have declined worldwide, generating interest in enhancement using hatchery‐reared individuals. In many cases, such restoration efforts have met with limited success due to high predator‐induced mortality rates. Furthermore, the mortality rates of outplanted hatchery abalone are often considerably higher than for wild individuals. This study uses northern abalone (Haliotis kamtschatkana) as a case study to determine whether hatchery‐reared abalone behave differently than their wild counterparts. In the field, outplanted hatchery‐reared abalone were significantly less responsive than wild abalone, in terms of number of abalone responding and intensity of response, to nearby movement and to physical contact with an inert probe. Also, when encountering a cue to which all abalone responded (a seastar predator), hatchery‐reared individuals remained subdued. Anti‐predator behavioural deficits in hatchery‐reared abalone were more pronounced in 4‐year‐old individuals than in 1‐year‐old individuals, suggesting an influence of either age or amount of time spent in the hatchery environment. These behavioural differences are expected to increase the vulnerability of hatchery‐reared abalone to predators, and are likely a major cause of their elevated predator‐induced mortality when outplanted.     

What are the drivers of the occurrence of illegal fishing and conservation barriers of sturgeons in the Caspian Sea?

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‘Whales eat fish’? Demystifying the myth in the Caribbean marine ecosystem

There has been much recent discussion about the idea that large whales are potential competitors with fisheries for available marine resources. Based on this idea, often referred to as the ‘whales eat fish’ conflict, culling whales has been proposed as a way to increase resources available for human consumption and thereby ensuring global food security. However, the scientific basis for such arguments remains unclear, especially in the Caribbean waters where baleen whales generally do not feed. In this article, we (i) develop an ecosystem model describing the trophic interactions between whales, fish and fisheries in the Caribbean waters, (ii) calculate the level of overlap between cetaceans and fisheries for food resources, and (iii) simulate the removal of cetaceans from the Caribbean waters in order to quantify the potential increase in available biomass of commercially important fish. Ten groups of cetaceans are considered in the model, including baleen whales, toothed whales and small cetaceans. Our results suggest that baleen whales are not a threat to fisheries in Caribbean waters, while toothed cetaceans seem to be more impacted by fisheries than they actually impacting them. Whales target different types of food resources and consume significantly less than what is taken by fisheries. Moreover, simulated reductions in large whale abundance do not produce any appreciable increase in biomass of the commercially important fish species. In some cases, the presence of some whales actually improves fishery yield as a result of indirect predation effects.     

Effect of dietary nutrient composition on the growth of olive flounder (<Emphasis Type="Italic">Paralichthys olivaceus</Emphasis>) with different feeding regimes

We have examined the effect of dietary nutrient composition on the growth, body composition and blood chemistry of juvenile olive flounder (Paralichthys olivaceus) maintained on two different feeding regimes. Three experimental diets [HP (high protein), HE (high energy) and IPE (intermediate protein and energy)] were crossed in a two-factor design with the two feeding regimes, which consisted of 2WS + 2WF (2-week starvation and then 2-week feeding) and 4WS + 4WF (4-week starvation and then 4-week feeding)], for 8 weeks. The total days of feeding in all treatments were the same. The final weight of fish was affected by feeding regime, but not by dietary nutrient composition. Long-term starving and feeding (the 4WS + 4WF treatments) yielded higher growth than the alternating short-term starving and feeding regime (2WS + 2WF treatments). The feed consumption of fish was affected by dietary nutrient composition, but not by feeding regime, while the feed efficiency of fish was affected by feeding regime, but not by dietary nutrient composition. Moisture, crude protein and crude lipid contents of the liver of the fish were affected by dietary nutrient composition, but not by feeding regime.