Effects of food colorants on photooxidation of lipids added to Alaska pollack <Emphasis Type="Italic">Theragra chalcogramma</Emphasis> surimi

Food colorants including rose bengal, erythrosine B, phloxine B and cochineal extracts were added to Alaska pollack Theragra chalcogramma surimi which was previously added with methyl linoleate (MeLe) or ethyl eicosapentaenoate (EPA Et). All the surimi were exposed to a 100-watt light tungsten bulb (4500 lux) in a cold room at 5°C. Four isomeric hydroperoxides, including 13-cis, trans-, 13-trans, trans-, 9-trans,cis- and 9-trans,trans-MeLe hydroperoxides, were generated by oxidation of MeLe added to surimi with and without cochineal extracts after exposure to light for several hours. For the surimi containing rose bengal, erythrosine B and phloxine B, extracted lipids contained not only the above four hydroperoxide isomers but also 12-cis,trans-as well as 10-trans,cis- MeLe hydroperoxides. EPA Et added to surimi which contained rose bengal, erythrosine B and phloxine B generated characteristic isomeric hydroperoxides, including 6-cis,trans- and 17-cis,trans-EPA Et hydroperoxides due to ¹O₂ mediated oxidation. The pro-oxidative potentials of four food colorants in surimi against added EPA Et or MeLe increased as the order of cochineal extracts < phloxine B<erythrosine B<rose bengal. These results clearly demonstrated that the addition of certain food colorants to surimi accelerated ¹O₂ mediated lipid oxidation to result in the generation of characteristic hydroperoxide isomers.     

Effect of Bay (Laurus nobilis L.) Essential Oil on Surimi Gels Nutritionally Enhanced with Salmon and Flaxseed Oils

Bay essential oil (BEO) at 0.5 and 1 g/100 g was added to surimi gels fortified with omega (ω)-3 rich oils. Although the fortification resulted in increased (P < 0.05) susceptibility of surimi to lipid oxidation, 0.5 g/100 g BEO significantly reduced TBARS (P < 0.05). Addition of ω-3 rich oil or BEO improved the texture. Color values of the surimi seafood were improved particularly when BEO was added. Sensory properties, water activity, and pH values were generally within the acceptable range. These results suggest that the incorporation of BEO may allow food manufacturers to nutritionally enhance surimi seafood with beneficial ω-3 rich oils.     

Functional morphology of chloride cells in killifish Fundulus heteroclitus, a euryhaline teleost with seawater preference

ABSTRACT:   Recent advances in the functional morphology of chloride cells in killifish Fundulus heteroclitus , a euryhaline teleost with seawater (SW) preference, were reviewed. Immunocytochemical detection of chloride cells with anti-Na⁺/K⁺-ATPase revealed transitional processes of the chloride cell distribution during early life stages. Chloride cells first appear in the yolk-sac membrane at an early embryonic stage, followed by their appearance in the body skin in the later embryonic stages. The principal site for the chloride cell distribution then shifts from the yolk-sac membrane and body skin during embryonic stages to the gills and opercular membrane in larval and later developmental stages. Morphologically distinct SW- and freshwater (FW)-type chloride cells were identified in adult killifish adapted to SW and FW, respectively. Both types of chloride cells are equally active in the two environments, but exert different ion-transporting functions. Following direct transfer of killifish from SW to FW, SW-type chloride cells were transformed into FW-type cells as a short-term response, followed by the promotion of chloride cell replacement as a long-term response. In killifish acclimated to low NaCl (0.1 mM) FW, intense immunoreactivity for vacuolar-type proton pump (V-ATPase) was detected in the basolateral membrane of FW-type chloride cells, whereas the immunoreactivity was much weaker in fish acclimated to FW with higher NaCl concentrations (1.0 and 10.0 mM). These results suggest the occurrence of active ion absorption in FW-type chloride cells and the involvement of V-ATPase in ion-absorbing mechanisms. In view of recent advances in this field, future chloride cell research should be considered in relation to the functional diversity of chloride cells.     

Seafood mislabelling: comparisons of two western European case studies assist in defining influencing factors,mechanisms and motives

The global seafood industry, influenced by consumer demand, is closely linked to the global fishing industry, which determines the variety of fish available for consumption. The recently revealed issue of seafood mislabelling threatens to weaken this link by removing consumer power to influence patterns of fisheries exploitation through informed choice. Recognizing this, there is an urgent need to go beyond the mere documentation of the phenomenon and learn more about the origins of this problem and the nature of factors influencing its occurrence to develop solutions. In an attempt to understand seafood mislabelling more thoroughly in Europe, 226 cod products were purchased from Ireland and the UK, genetically identified using a DNA barcoding technique (COI barcoding gene), and species identification results were compared against product labels. Cod mislabelling proved more severe in Ireland than in the UK (28.4% vs. 7.4%). Moreover, whereas data show that in Ireland, cheaper species are sold as cod, in the UK, threatened Atlantic cod (Gadus morhua) may be sold as ‘sustainably sourced’ Pacific cod. Considering these countries operate under the same EU policies for seafood traceability and labelling, it is likely that this situation has been influenced by heightened consumer awareness in the UK, which has created an environment where mislabelling is discouraged. In addition to identifying samples, traceability information from packaged cod was used to trace products back to supplying companies. Although inconclusive in determining blame, this exercise has demonstrated that using traceability information can add explanatory power when attempting to determine responsibility for the occurrence of mislabelling.     

Quality and Shelf Life of Liver of Farmed Cod (Gadus morhua)

ABSTRACT

Livers of Atlantic cod (Gadus morhua) are traditionally used in cod liver oil production or consumed cooked or canned. The farming of cod is a relatively new industry in Norway. The aim of this study was to determine quality and shelf life of fresh liver from farmed cod during chilled storage on ice by hydrolysis and oxidation state and sensory quality and the influence on canned liver. In two experiments, livers from farmed cod were stored chilled and sampled from Days 0 to 13, respectively. Quality, measured as hydrolytic and oxidation degradation, was reduced after 7 days of storage, while sensory quality was reduced after 4 days. Free fatty acids increased from Day 7 in both experiments, while peroxide value and anisidine value showed no change when the livers were single wrapped. Rancid odor was the first sign of oxidation and was registered after three to four days of storage. Canning within 2 days of storage prevented leakage of oil from the canned livers. Sensory analyses of oxidation are recommended as a sensitive and rapid method to detect oxidation of chilled cod liver.     

Solubility of Cod Muscle Myofibrillar Proteins at Alkaline pH

Abstract

The solubility characteristics of proteins are of interest because of their relation to many functional properties. The solubility of the proteins of washed cod muscle mince increased dramatically between pH 8.9 and 9.2 at an ionic strength of 10 mM, whereas a high but constant solubility was observed at 430 mM sodium chloride over the pH range from 7 to 9.5. At pH 9.2, the proteins of the washed cod muscle were greater than 60% soluble at a sodium chloride concentration of 6.6 mM but were salted out at slightly higher concentrations. Above about 100 mM to about 900 mM salt, the proteins were salted in, and greater than 90% solubility was achieved. Maximal extractability was observed with a ratio of 36 volumes of extracting solution to 1 weight of minced muscle at pH 9.2. At pH 8.5, the extractability of the protein increased from 11% to 24% over a range in extraction volumes of 12:1 to 144:1 of volume of extracting solution to muscle tissue weight.     

Occurrence of Francisella piscicida in farmed and wild Atlantic cod, Gadus morhua L., in Norway

Francisellosis, caused by the bacterium Francisella piscicida , has become one of the most serious diseases in Atlantic cod production in Norway. The major aim of this study was to determine the distribution of F. piscicida in farmed and wild fish in areas with cod farming along the Norwegian coast, and its occurrence in cod from areas without cod farming. Two real-time PCR assays, targeting the 16S rRNA gene and the FopA gene of F. piscicida , were developed since sensitive and specific diagnostic tools are required for detecting asymptomatic carriers of the bacterium. A total of 422 wild cod from 13 sampling areas and 955 farmed cod from 10 areas along the coast of Norway were examined. Using the real-time polymerase chain reaction (PCR) assays, F. piscicida was detected in wild populations of cod from all counties examined south of Sogn og Fjordane in southern Norway (overall prevalence 13%, n  = 221). Wild cod north of Sogn og Fjordane were negative for the bacterium ( n  = 201). Farmed cod from most parts of Norway were F. piscicida positive. The apparent absence of the bacterium in wild populations of cod in the northern parts of Norway and its widespread occurrence in wild cod from southern parts of Norway is believed to relate to differences in seawater temperatures.     

Efficacy of various lipid supplements in formulated pellet diets for juvenile Scylla serrata

Efficacy of sunflower oil (diet SF) and soybean oil (diet SB) alone and in combination with cod liver oil (diets M1‐2.80:1.40:1.40, M2‐2.80:2.24:0.56 and M3‐2.80:0.56:2.24; cod liver oil:sunflower oil:soybean oil) as lipid supplements (5.6%) in formulated diets (crude fat ～9.79%) for juvenile Scylla serrata (weight=0.28±0.07 g, carapace width=9.7±0.1 mm) were compared with diet CL, containing cod liver oil alone as the lipid supplement (6 diets × 24 crabs stocked individually, randomized block design). Growth performance, nutrient (protein and lipid) intake and gain of crabs fed M1, M2 and M3 were higher (P≤0.05) than the crabs fed SF and SB, but were not significantly different (P≥0.05) from crabs fed CL. Dietary fatty acids (FAs) are found to influence the FA profile of test crabs. Higher tissue levels of 16:1n‐7, 18:1n‐9 and 18:1n‐7 reflected the essential FA deficiency in crabs fed diets supplemented only with vegetable oils. Results confirmed that S. serrata could utilize vegetable oil supplements in the formulated diets as a partial replacement (50%) of cod liver oil without compromising growth and survival. Partial substitution of marine fish oil with suitable vegetable oils can reduce the feed cost considerably, in the context of rising fish oil prices.     

Effects of environmental Ca2+ levels on branchial chloride cell morphology in freshwater-adapted killifish Fundulus heteroclitus

ABSTRACT: To examine the involvement of chloride cells in the uptake of Ca²⁺ in freshwater (FW) killifish, chloride cell morphology was compared in fish acclimated to different defined FW environments with Ca²⁺ concentrations of either 0.1 mM, 0.5 mM, or 2.5 mM. Numerous chloride cells were detected in whole-mount preparations of the gill filaments, which were stained with an antiserum specific for Na⁺, K⁺-ATPase. Chloride cells, located mostly on the afferent–vascular edge of the filaments, were larger at lower Ca²⁺ concentrations. Electron microscopic observations showed that in the 0.1 mM and 0.5 mM Ca²⁺ experimental groups, the apical membrane of chloride cells were flat or slightly projecting and equipped with numerous microvilli. In the 2.5 mM Ca²⁺ group, some chloride cells formed an apical pit, whereas other cells were similar to those observed in the 0.1 mM and 0.5 mM Ca²⁺ groups. Plasma osmolality decreased with decreasing ambient Ca²⁺ concentration, suggesting that environmental Ca²⁺ affects the permeability of the body surfaces. Gill Na⁺, K⁺-ATPase activity in the 0.1 mM and 0.5 mM Ca²⁺ groups were significantly higher than that in the 2.5 mM Ca²⁺ group, implying the involvement of the Na⁺–Ca²⁺ exchanger in Ca²⁺ uptake in the gills. These findings suggest that chloride cells function as the site for Ca²⁺ uptake in killifish acclimated to low Ca²⁺ environments.     

Enhancing highly unsaturated ω‐3 fatty acids in phase‐fed rainbow trout (Oncorhynchus mykiss) using Alaskan fish oils

Rainbow trout, average weight 185–187 g, were fed feeds containing menhaden oil, canola oil or fish oils (pollock, pink salmon or rockfish) produced from Alaskan seafood processing waste as the added oil for 8 weeks, at which time the fish weighed 391–411 g (average 404 g, pooled SE = 5.7). The fish were previously fed from 75 g average weight fed commercial feed containing poultry oil as the added oil. No significant differences were measured in final weight or feed conversion ratio among dietary treatment groups. Significant differences were found in fillet ω‐3 fatty acid (FA) levels from fish receiving fish oil‐supplemented feeds compared to those from fish receiving feeds containing canola oil. Fillet contents of eicosapentaenoic acid (EPA; 20:5ω3) and decosahexaenoic acid (DHA; 22:6ω3) were highest in the pollock oil treatment group, although all fish oils increased highly unsaturated ω‐3 FA contents (mg 100 g^?1) of fillets. Fish oil used through the production cycle was reduced by 25% by supplementing feeds with poultry oil during the middle phase of production (75–175 g) compared to using feeds containing fish oil throughout the production cycle. Fish oils recovered from Alaskan seafood processing waste were suitable alternatives to conventional fish oil as ingredients in rainbow trout production feeds.     

Pressure Inactivation of Enteric Viruses in a Seafood Salad-Like Product

High pressure processing (HPP) is a nonthermal processing technology that can inactivate foodborne viruses. This study assessed the protective effects of food components on virus inactivation by HPP in a seafood salad model. Virus-inoculated seafood samples (cod, shrimp, tuna, and clams) with or without mayonnaise were pressure-treated at 5°C. The seafood salad provided a protective effect on HPP inactivation compared to cell culture medium. Inactivation in seafood salad varied greatly due to the complex nature of the food matrix. When seafood salad ingredients were isolated, mayonnaise alone had a 2.0-log₁₀ PFU/g protective effect for all viruses, unlike albumin, which did not affect virus inactivation, providing some insight into the roles individual ingredients may play on HPP inactivation of viruses in foods.     

Effects of dietary oxidized oil and vitamin E on the growth,blood parameters and body composition of juvenile Atlantic cod Gadus morhua (Linnaeus 1758)

The effects of oxidized dietary lipid and the role of vitamin E on the growth performance, blood parameters and body composition of juvenile Atlantic cod (Gadus morhua) were evaluated over a 9‐week feeding period. Four isonitrogenous experimental diets containing fresh or oxidized fish oil with or without added vitamin E (α‐tocopherol or mixed tocopherols) were fed to juvenile cod. The oxidized lipid used had a peroxide value of 94 mEq kg^?1 oil. No significant (P>0.05) differences in growth performance (weight gain and specific growth rate) or feed utilization (feed consumption and feed efficiency ratio) were observed when oxidized dietary lipid was used. The hepatosomatic index (HSI), viscerosomatic index (VSI) and haematocrit did not show any significant (P>0.05) differences among the treatments. However, erythrocyte osmotic fragility (EOF), referred to as susceptibility to haemolysis, of fish fed oxidized oil without added vitamin E was high in comparison with those fed unoxidized oil. Supplementation with α‐tocopherol appeared to decrease haemolysis, but mixed tocopherols had no significant (P>0.05) effect on EOF. The proximate composition of fish whole body was also affected by diet treatment. Fatty acid composition of liver total lipid reflected that of dietary lipid. Variations in tissue (liver and muscle) fatty acid composition among the treatments followed the same trend as those of the dietary fatty acids. Fish fed fresh oil had a higher proportion of polyunsaturated fatty acids (PUFA) in muscle and liver lipid than those fed oxidized oil. The results suggest that oxidized dietary oil affected juvenile Atlantic cod in certain tissues and that these effects could be alleviated by supplementation of sufficient amounts of vitamin E in the diet.     

Preparation of algal-oligosaccharide mixtures by bacterial agarases and their antioxidative properties

ABSTRACT:   Algal-oligosaccharide-lysates (AOL), derived from six agars and four algal polysaccharide extracts (APE), were treated with 100–500 activity units (AU) of MA103-agarases or MAEF108-agarases, and their antioxidative properties evaluated. Soluble total polyphenols (TP) were between 462.2 ± 1.6 gallic acid equivalents (GAE, µg/mL) and 70.6 ± 17.4 GAE. The DPPH radical scavenging capacity of all AOL went from 68.3 ± 0.7% to 0.5 ± 0.1%. The ferrous ion chelating capacity of all AOL went from 93.1 ± 0.2% to 21.7 ± 0.9%. Evaluation of the H₂O₂ scavenging capacity of all AOL was between 35.9 ± 5.4% and 0.1 ± 0.2%. The reducing power of all AOL went from 51.3 ± 2.6 to 3.2 ± 6.8 expressed as µg/mL ascorbic acid. In DPPH radical scavenging capacity, ferrous ion chelating capacity and reducing power etc., the AOL derived from the APE of Porphyra dentate (digested by 500 AU of MAEF108-agarases) were highest, in all test sets. However, the AOL derived from the APE of Monostroma nitidum (digested by 500 AU of MAEF108-agarases) had the highest H₂O₂ scavenging capacity in all test sets. The order of antioxidative activity performance of all AOL treated in this experiment, by these four antioxidative methods, is as follows: ferrous ion chelating capacity > DPPH radical scavenging capacity > H₂O₂ scavenging capacity > reducing power; this may be related to their polyphenols, small molecular weight polysaccharides or simple sugar constituents. In this study, it is demonstrated that various agarases derived from algal oligosaccharide mixtures possess good potential for use as a health food, due to their antioxidative capacity.     

The spatial distribution of cod (Gadus morhua L.) spawning grounds in the Kattegat, eastern North Sea

Similar to many other commercial marine fish species, Atlantic cod (Gadus morhua L.) migrate towards specific sites at spawning. These temporal aggregations are generally the most targeted by the commercial fishery. The Kattegat cod has undergone a substantial reduction over the past 25 years and both stock size and spawning stock biomass have remained at very low levels since the end of the 1990s. There is, therefore, an urgent need to map and document spawning grounds still in use. In the present study, spawning sites of Atlantic cod were identified in the Kattegat using a combination of commercial and fishery independent data from 1996 to 2004. Moreover, putative spawning and non-spawning areas were also sampled before and during the reproductive season between 2002 and 2006, and the proportion of mature females together with the individual physiological status were used to validate and strengthen the spatial analyses.

The spatial analyses identified several spawning areas in the region and two areas in the southeastern part of the Kattegat which appeared to be the most important. The results showed the presence of cod spawning aggregations, although reduced in size, in areas that have been utilized for more than 25 years according to historical information. Some local spawning grounds may have also disappeared. The proportion of mature females was higher in putative spawning than in non-spawning areas (p < 0.001) and females from spawning areas had higher gonadosomatic (p < 0.05) and hepatosomatic (p < 0.001) indices than those from non-spawning areas.

Knowledge of stock spatial and temporal distribution is essential in designing recovery strategies for depleted fish populations. The unambiguous stability of the locations of spawning aggregations over time, as shown in this study, represents a useful aid in order to efficiently implement a recovery plan for the collapsing cod stock in this area.     

Inclusion of camelina meal as a protein source in diets for farmed Atlantic cod Gadus morhua

Camelina meal Camelina sativa (CM) is a potential protein source in aquaculture feeds, because of its crude protein level (39%) and essential amino acids. Two feeding experiments were conducted with Atlantic cod Gadus morhua. Cod in Experiment I (19.4 g fish^?1) were fed diets with 0%, 12% or 24% CM for 9.5 weeks at 10°C; and cod in Experiment II (14.4 g fish^?1) were fed diets with 0%, 15%, 30% or 40% CM for 13 weeks at 10°C. Growth, lipid and amino acid tissue composition were compared amongst cod fed varying levels of CM. In Experiment I, cod could tolerate the highest level of CM inclusion (24%) without affecting growth compared to cod fed the control diet. In Experiment II, growth performance was significantly affected at 30% CM inclusion compared to the control treatment, and cod fed 15% CM displayed some signs of depressed growth (reduced feed intake and weight gain). Both treatment and duration were interacting factors (P = 0.015) that determined growth performance when comparing both experiments. Muscle tissue composition was relatively unaltered with less than 30% CM inclusion; however, multivariate statistics revealed significant differences in muscle tissue fatty acid composition between cod fed 40% CM and the control diet. The tissue amino acid profile was generally unaltered because the dietary amino acid profile was consistent after CM inclusion. A few antinutritive compounds in CM may have affected palatability in diets with greater than 30% CM inclusion, which may have resulted in reduced growth performance.     

Murray cod an apex predator in the Murray River, Australia

Abstract –  To determine if the Murray cod Maccullochella peelii peelii is an apex predator in the lowland rivers of the Murray-Darling Basin, its feeding ecology was compared with that of the sympatric top predator, golden perch Macquaria ambigua ambigua based on samples supplied by recreational anglers. Diet and prey size were reconstructed from alimentary tract contents of Murray cod ( N  = 39) and golden perch ( N  = 52), and their feeding morphology was assessed and included calculation of length–gape relationships and relative gut index. Both species fed principally on fish and decapods although Murray cod was the more piscivorous (frequency of occurrence 44% versus 6%, total number 50% versus 2%, total weight 90.4% versus 16.0%). Based on reconstructions of prey sizes, fishes up to 1 kg in weight were preyed on by Murray cod, distinguishing it from other top predatory fishes in the Murray-Darling Basin and supporting its classification as an apex predator.     

Effect of dietary saturated and monounsaturated fatty acids in juvenile barramundi Lates calcarifer

Barramundi (Lates calcarifer), a catadromous teleost of commercial interest, perform well when fed a wide range of dietary oils. However, the range of alternative oils now being explored is typically rich in saturated and monounsaturated fatty acids (SFA and MUFA). In this study, the response of juvenile barramundi (47.0 g per fish initial weight) fed isolipidic and isoenergetic diets with 82 g kg^?1 added oil was tested. The experimental test diets had a 2 : 1 or 1 : 2 ratio of SFA to MUFA (SFA‐D and MUFA‐D, respectively) compared to a control diet (CTRL‐D) fed for 8 weeks. The diets containing mostly olive oil (dietary MUFA‐D) and mostly refined palm oil (dietary SFA‐D) did not impact the growth performance or feed utilization parameters of the barramundi. The in vivo beta‐oxidation activity was consistent with the dietary fatty acid composition, with the most dominant FA being heavily beta‐oxidized. Together, the in vivo whole‐body mass balance of fatty acids showed that n‐3 long‐chain polyunsaturated fatty acids (LC‐PUFA) were most efficiently utilized in the SFA‐D‐ and MUFA‐D‐fed fish. This study provides evidence that additional dietary MUFA and SFA are suitable lipid classes for juvenile barramundi and they are both equally efficient at sparing LC‐PUFA from an oxidative fate.     

Effects of thyroxine,cod liver oil and potassium iodide on growth and survival of juvenile seahorse,Hippocampus barbouri

Low survival at early stage is the bottleneck in seahorse aquaculture, particularly in the feeding aspect since newborn seahorses must feed immediately upon birth to sustain themselves. Seahorses are visual predator, therefore preferred live feed such as zooplankton. In aquaculture, the most common live feed used is Artemia. In this study, two experiments were conducted to determine the effect of different Artemia enrichment on the growth and survival of newborn Hippocampus barbouri. In the first experiment, six treatments using Artemia enriched with Culture Selco Plus? (SELCO), thyroxine (T4), potassium iodide (KI), cod liver oil (CLO), cod liver oil in combination with thyroxine (CLO + T4) and potassium iodide (CLO+KI) were fed to newborn H. barbouri. Newly hatched Artemia were used as control. At the end of first experiment, treatments using CLO + T4 produced juvenile H. barbouri with the best (p < .05) wet weight (0.142 ± 0.000 g), while juvenile in treatment CLO+KI recorded the highest (p < .05) standard length (3.947 ± 0.014 cm). Subsequently, a second experiment was carried out using the two best enrichment (CLO + T4 and CLO + KI) from the first experiment, but given at different frequency (daily, twice a week, once a week, once in 2 weeks). Daily enrichment using both CLO + T4 and CLO + KI showed no significant (p > .05) difference in growth performance and survival of juvenile of H. barbouri. Interestingly, juvenile fed CLO + T4 enriched Artemia at frequency of twice a week also has no significant difference (p > .05) in survival and growth performance (except for final standard length) when compared with treatment CLO + T4 at daily frequency.     

Effects of ontogeny, temperature, and light on vertical movements of larval Pacific cod (Gadus macrocephalus)

The role of behavior, especially vertical migration, is recognized as a critical component of realistic models of larval fish dispersion. Unfortunately, our understanding of these behaviors lags well behind our ability to construct three-dimensional flow-field models. Previous field studies of vertical behavior of larval Pacific cod ( Gadus macrocephalus ) were limited to small, preflexion stages (≤11 mm SL) in a narrow range of thermal conditions. To develop a more complete picture of larval behavior, we examined the effects of ontogeny, temperature, and light on vertical responses of larval Pacific cod in experimental columns. While eggs were strictly demersal, yolk-sac larvae displayed a strong surface orientation as early as 1 day post hatch (∼ 5 mm SL). Consistent with field observations, small preflexion larvae (<10 mm SL) showed no response to varying light levels. However, there was a direct effect of temperature on larval behavior: Pacific cod larvae exhibited a stronger surface orientation at 4°C than at 8°C. The behavior of larger, postflexion larvae (>15 mm SL) in experimental columns was consistent with a diel vertical migration and independent of water temperature: fish were more widely distributed in the column, and median positions were consistently deeper at higher light levels. These laboratory observations are combined with observations from discrete-depth (MOCNESS) sampling in the Gulf of Alaska to characterize the vertical distribution of larval Pacific cod and contrast ontogenetic patterns with walleye pollock ( Theragra chalcogramma ). The vertical movements of larval Pacific cod described here will be applied in the development of dispersal projections from Gulf of Alaska spawning grounds.     

Evaluation of a simple means to reduce discard in the Kattegat-Skagerrak Nephrops (Nephrops norvegicus) fishery: Commercial testing of different codends and square-mesh panels

Discarding of fish species in the Kattegat-Skagerrak Nephrops directed fisheries remains at high levels. In this work we have tested four sets of codends pair-wise with the catch comparison technique under full commercial conditions to assess their potential in reducing the catch of undersized commercial species, in particular cod. We investigate the position of a 90 mm square-mesh panel (SMP), the effect of increasing the mesh size from 90 to 120 mm in the SMP, the effect of inserting a 90 mm SMP in an 80 mm codend and the effect of increasing the codend mesh size from 90 to 120 mm in a total of 89 hauls. Inserting the SMP 3–6 m from the codline compared to 6–9 m from the codline, reduced catches of cod above the minimum landing size (MLS) and Nephrops above and below the MLS. Increasing the mesh size in the SMP from 90 to 120 mm increased the catch of cod above the MLS in weight with an overall increase of 12% in the revenue. The effect of installing a 90 mm SMP 6–9 m from the codline in a nominal 80 mm codend had no effect on the catch of cod. Increasing the nominal codend mesh size from 90 to 120 mm reduced the catch of all species below the MLS, except monkfish. Catches of Nephrops above the MLS were, however, reduced by approximately one third and the total loss in revenue was 21%.