Nutritional composition, quality and spoilage capacity of orange roughy (Hoplostethus atlanticus) from the North East Atlantic

The nutritional composition o f orange roughy (collected from the Northeast Atlantic near the Rockall Trough) was studied on a seasonal basis. In addition samples were aged and stability assessed. Protein levels (16.68-16.21% w/w) were found to be slightly higher than those recorded for the N ew Zealand species o f orange roughy and compared favourably with protein values for fish muscle in general. Statistically results show a significant seasonal variation with no variation from fish to fish or in the location within the fish. Lipid content (3.6-4.5% w/w) was found to be much lower than that recorded for New Zealand. As with protein statistically results show a significant seasonal variation and no variation from fish to fish or in the location within the fish. Moisture levels (77.3_79.6%w/w) compared favourably with values obtained from other studies. Again statistically results show a significant seasonal variation with no variation from fish to fish or within the fish. Iodine values (74.63-79.54) indicate the likely presence o f a high level o f mono unsaturated fatty acids. Statistically results show no significant seasonal variation and no sample variation or variation within fish. Thin layer chromatography o f the extracted fat showed the major type to be wax esters with a much lower amount o f triglycerides and smaller amounts of polar lipids, free sterols and free fatty acids. Total fatty acid composition was found to be very similar to that recorded from other studies and showed that most o f the oils extracted from the fish muscle contained a high percentage o f mono unsaturates namely 16:1,18:1, 20:1 and 22:1 (85.63 - 91.14% ) with 16:1 present in the smallest amounts and 18:1 the major one. The only saturated fatty M.Sc. in Biochemistry III Nutritional Composition, Quality and Spoilage Capacity of Specific Deep Sea Fish acids present in significant quantities were 14:0, 16:0 and 18:0, the total varied from a seasonal average high o f 4.05 % to an average low o f 2.27%. The polyunsaturated fatty acids linoleic and arachidonic acid were present in small quantities varying in total from 0.89% to 1.50%. Docosapentaenoic acid (D P A ) was found only in trace quantities in spring, autumn and winter samples and undetected in summer. Levels o f Eicosapentaenoic acid (EPA ) and Docosahexaenoic acid (D H A ) were also found in very low percentages and varied on a seasonal basis with average values ranging from 0.41% in summer to 1.03 % in autumn for EPA and from 1.44 % in summer to3.20 % in autumn for D H A . Again statistically results show a significant seasonal variation with no variation from fish to fish or location within the fish. Levels o f freshness were measured using the Thiobarbituric acid (T B A ), Total volatile base nitrogen (T V B -N ) and Trimethylamine (T M A ) techniques. The quality o f the fish upon arrival was excellent and well below legal/acceptable lim its.T V B -N values ranged from 6.88-8.91 mg/lOOg and T M A values from 4.82-6.46 mg/lOOg Values for T B A ranged from 0.18-0.35 mg Malonaldehyde/kg fish. The summer values were higher than the other seasons. Seasonal variation was significant for all methods with no variation from fish to fish or within the fish. Fish aged at +4°C in air did not exceed the T V B N lim it o f 35mg/100g until day 6 whereas the T V B N lim it was extended to 8 days for fish aged at +4°C in vacuum. However the T M A lim it o f 12mg/100g was reached on day 4 for fish stored at +4°C in air and on day 5 for vacuum packed samples stored at +4°C . Fish stored at -5°C in air and vacuum packed did not reach the T V B N lim it until day 61 but the T M A limit was reached on day 24 for fish stored at -5°C in air and was extended to 31 days for vacuum packed fish stored at-5°C. Prolonged storage at -18°C caused some deterioration o f the frozen fish muscle. Upon thawing the shelf life o f fish stored for 12 months was much shorter than that stored for 6 M.Sc. in Biochemistry IV Nutritional Composition, Quality and Spoilage Capacity of Specific Deep Sea Fish months. This in turn deteriorated faster than fresh fish held at refridgeration temperature in air. Orange roughy were found to be a good source of protein with moisture levels similar to that o f other fish. They were o f medium fat content but have a very poor content o f the essential omega 3 and omega 6 fatty acids. Orange roughy can be stored at -18°C but its subsequent refridgerated shelf life will be shorter than that o f unfrozen orange roughy stored at refridgeration temperature. Orange roughy are a very important part o f the ecosystem. Their composition is less nutritionally beneficial than more readily available fish for human consumption and therefore should not be fished at all

Evaluation of fish pots as a feasible fishing method in Irish waters, with specific reference to the physiological effects of common and alternate pots on the lesser spotted dogfish (Scyliorhinus canicula).

Finfish pots have emerged as a “responsible” gear, when used in combination with conservational and technical measures to sustain fisheries. Previous trials in Irish waters have offered no published reported data and so three designs tested in the current study provide new information on this gear. The most successful traps in terms of fish catch were rigid steel framed rectangular pots used to target Conger eel. Although commercial yield was low (0.2 per trap haul), potential existed for a viable pot fishery. Deployment and storage of Norwegian floating pots was conducted with relative ease but performance in the water was poor resulting in loss of gear. Catch returns were notable even though effort was restricted as mega-faunal by-catch was a problem, which lead to ending this trial. From these initial trials it was evident that catch rates were low compared to established Norwegian fisheries (3.6 cod per pot), which resulted in the utilisation of pots, already established in the crustacean fishery, to find species readily accessible to pot capture. Although fished and designed differently, these gears provided an opportunity to establish the benefits of pot fishing to fish quality and to determine the effects on by-catch. The fishing effects of three catching methods (pots, angling and trawl) and the effects of air exposure on the physiological status of a common by-catch, the lesser spotted dogfish Scyliorhinus canícula (L.) were examined using a range of physiological biomarkers (plasma catecholamine, glucose, lactate, muscle pH and muscle lactate). Physiological responses of fish to an emersion stress regime resulted in a significant metabolic disturbance in groups, but may not have weakened the overall health of these fish, as signified in the revival of some metabolites. Plasma glucose and lactate concentrations did not however recovery to baseline levels indicating that to achieve an accurate profile, responses should be determined by a suite of biomarkers. Responses did not demonstrate that samples from the pots were significantly less stressed than for the other two methods; angling and trawling, which are in contrast to many other studies. Employment of finfish potting therefore in Irish waters needs further consideration before further promotion as a more responsible method to supplement or replace established techniques.

Effects of selected post harvest processes on brown crab (Cancerpagurus L.) and European lobster (Homarus gammarus L.) from Irish Crustacean Fisheries

The crustacean fishery is important to the socio economics of rural and island communities around Ireland; with brown crab (Cancer pagurus) and European lobster (.Homarus gammarus) being the most valuable shellfish species. Brown crab and lobster are marketed live with the majority being exported from Ireland to southern Europe. Post capture processes used in Ireland are very subjective but promote fresh, live products. Common practices used in the crustacean fishery include nicking of brown crab and long term storage of lobster. This study showed that nicking resulted in elevated mean lactate levels of 17.90% (StDev ± 1.74) and elevated mean glucose levels of 120.55 % (StDev ± 0.26) with mean circulating bacteria levels 9 times greater in nicked crab. Nicking resulted in 96.3% increase in tissue necrosis and a subsequent reduction in product quality. These factors possibly compromise the host’s defense system, which may ultimately reduce the animal’s ability to cope with additional stressors caused by post-harvest processes. Long term storage allows lobster to be stored until the market is less saturated and prices are higher. This investigation found that some lobsters contracted bacterial biofilms as a result of long term storage. Bacteria isolated from biofilms were identified as Arcobacter and Campylobacterales with identity and alignment scores of 80% andd 88% respectively.

Age, growth and reproductive biology of Plaice, (Pleuronectes platessa L.) in Irish waters, 2003-2005

The current study presents data on age and growth for plaice (Pleuronectes platessa L.) sampled between November 2003 and February 2005 in ICES areas Via (northwest coast of Ireland), Vila (Irish Sea), Vllg (Celtic Sea), VDj (southwest coast of Ireland) and VHb (west coast of Ireland), and data on the reproductive biology and maturity of plaice in ICES area Vllb (west coast of Ireland). This is the first detailed account of the biology of plaice for some of these areas. It is intended that this study will improve understanding of the life cycle of plaice and help fisheries scientists to better predict the effect of fishing effort on Irish plaice stocks. The overall length range found for plaice was 9-51.99cm TL, with a length range of 9-5 lcm TL for females and 9-40cm for males. In all ICES areas the length range for female fish was larger than for male fish. The age range of plaice sampled during this study was 1 to 16 years. In all ICES areas females had a greater range in ages and fish in the larger age groups. From analysis of length and age data it was concluded that there was a significant difference (P=0.000) in growth rate of males and females between ICES areas sampled in March 2004. The highest rate of fishing mortality was determined for ICES area Via (F=1.06) and the lowest for ICES area Vila (F=0.56). In each ICES area male and female plaice have fully recruited to the population by age 4, with the exception of females in ICES area Via, for which a tr value of 5 years was determined. Length at first maturity (L50%) was determined to be 23cm and 21cm for males and females respectively. Age at first maturity (A50%) was determined to be 3 years for both males and females. It was found that males and females in ICES areas Vllb, Vila and Via are well above the length and age at first maturity when they are recruited to the fishery. In ICES area Vllb female plaice spawn from November to March, with peak spawning occurring in February, and male plaice spawn from November to April, with peak spawning occurring in November. Spawning females had an age range of 2 to 10 years and spawning males had an age range of 2 to 7 years. From the oocyte length frequency distributions, it was determined that the plaice is a determinate batch spawner. During this investigation a total of 177 ovaries and 127 testes were staged using both macroscopic and histological criteria. The overall percentage of maturity stages which compared favorably between the two assessment methods was 22.03% for female plaice and 37.80% for male plaice. In general, the findings of this study indicate that there was a very poor match between the macroscopic and histological assessment methods. Given that the histological determination of these stages is based on the observation of a distinct set of developmental features, it is expected that it would be more accurate to use histologically assessed gonads to calculate the annual percentage maturity assessment. The biology of plaice in the areas studied is compared with previous studies of plaice in Irish and European waters.