Population dynamics of O-group plaice, Pleuronectes platessa L., on sandy beach nursery grounds in Galway Bay, the West Coast of Ireland, 2002 to 2006.

The recruitment of 0-group plaice to sandy beach nursery grounds in Galway Bay was examined, using a Riley push-net, from February to June in 2005 and 2006. Sampling was carried out every two weeks on spring tides. Three beaches were sampled, Ballyloughan, Silverstrand and Glann na Ri. Archived 0-group plaice, for Ballyloughan and Silverstrand, from 2004, were processed. Results were compared to findings from a previous study carried out in 2002 and 2003 (Allen 2004). Otolith microstructure analysis was used to determine hatching dates, larval duration, settlement dates, post-larval age and daily growth rates of 0-group plaice in April and May 2005. Results were compared to a previous study (Allen 2004). Hatching dates in Galway Bay ranged from late January to early April in 2005. No significant difference in hatching dates was observed between years or between beaches sampled. Larval duration of 0-group plaice in Galway Bay ranged from 21 to 45 days for fish sampled in April and May 2005. No significant difference was observed in larval age between beaches sampled in Galway Bay or between years in April 2003 and 2005. A significant difference was observed between larval age and years in May 2003 and 2005, however no significant difference was observed between beaches. Settlement timing was calculated using push-net data and otolith microstructure analysis. Settlement of 0-group plaice in Galway Bay generally started in early March and finished in May. Settlement patterns, calculated using otolith microstructure analysis, in 2003 and 2005, were not significantly different to one another. There was also no difference in settlement patterns between the beaches sampled. Results from the present study showed no spatial difference in the pelagic life cycle stages of fish caught in April and May 2003 and 2005.

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

Data for the sustainable management of an emerging fishery: Age, growth and stock structure of Atlantic saury Scomberesox saurus saurus (Walbaum), in the Northeastern Atlantic Ocean

Almost half of Ireland’s commercial stocks face overexploitation. As traditional species decrease in abundance and become less profitable, the industry is increasingly turning to alternate species. Atlantic saury (Scomberesox saurus saurus (Walbaum)) has been identified as a potential species for exploitation. Very little information is available on its biology or population dynamics, especially for Irish waters. This thesis aims to obtain sound scientific data, which will help to ensure that a future Atlantic saury fishery can be sustainably managed. The research has produced valuable data, some of which contradicts previous studies. Growth of Atlantic saury measured using otolith microstructure is found to be more than twice that previously calculated from annual structures on scales and otoliths. This results in a significant reduction of the expected life span from five to about two years. Investigation of maturity stage at age indicates that Atlantic saury will reproduce for the first time at age one and will survive for one or at most two reproduction seasons. It is concluded that a future Irish fishery will target mostly fish prior to their first reproduction. Finally the thesis gives some insights into the population structure of Atlantic saury, by analysis of otolith morphometric. Significant differences are detected between Northeastern Atlantic and western Mediterranean Sea specimens of the 0+ age class (less than one year old). The implications of these results for the management of an emerging fishery are discussed.