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.

Studies on the effects of selected trace metals on Matapenaeus Dobsoni (MIERS)

This thesis is an attempt by the author to assess the suitability of Metapenaeus dobsoni (Miers), an economically important crustacean species as a sentinel organism of trace metal pollution. The results of detailed investigations on seasonal variation, bioassay, accumulation and depuration of three metals viz., mercury, copper and zinc are presented and discussed. The importance of trace metals in the aquatic environment and their present status in the study area - Cochin backwaters, the significance of crustacean fisheries, the species M. dobsoni and the objectives of the present studies are described in Chapter 1. The methodology adopted during the investigation is given in Chapter 2. Chapter 3 delineates the seasonal variation of Hg, Cu and Zn in the edible and non-edible parts of M. dobsoni collected from Cochin backwaters for a period of one year (June 1984-May 1985). The results of bioassay experiments are given in Chapter 4. Kinetics of accumulation ,retention and depuration of trace metals, their biological half-life, the influence of size group and environmental factors are given in Chapter 5. The effect of these metals on the physiological response of M. dobsoni viz. oxygen consumption is included in Chapter 6. A summary and list of references are also appended.

Literature review of elasmobranch bycatch and retention rate

To address growing concern over the effects of fisheries non-target catch on elasmobranchs worldwide, the accurate reporting of elasmobranch catch is essential. This requires data on a combination of measures, including reported landings, retained and discarded non-target catch, and post-discard survival. Identification of the factors influencing discard vs. retention is needed to improve catch estimates and to determine wasteful fishing practices. To do this we compared retention rates of elasmobranch non-target catch in a broad subset of fisheries throughout the world by taxon, fishing country, and gear. A regression tree and random forest analysis indicated that taxon was the most important determinant of retention in this dataset, but all three factors together explained 59% of the variance. Estimates of total elasmobranch removals were calculated by dividing the FAO global elasmobranch landings by average retention rates and suggest that total elasmobranch removals may exceed FAO reported landings by as much as 400%. This analysis is the first effort to directly characterize global drivers of discards for elasmobranch non-target catch. Our results highlight the importance of accurate quantification of retention and discard rates to improve assessments of the potential impacts of fisheries on these species.

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.

The works of Martin Doyle [pseud.] containing I. Hints to small farmers on land, fences, cottages, potatoes, mangel wurzel, turnips, manures, &c. II. Hints on road-work, ventilation, health, dress, temperance, education, &c. III. Hints on planting, cattle, fowls, fisheries, agricultural implements, flax, &c. IV. Irish cottagers.

Each work has also special t-p. and titles vary from those on main t.-p. I. Hints originally intended for small farmers of the county of Wexford ... 7th ed., rev. and enl. 1831. II. Hints addressed to the small holders and peasantry of Ireland on road-making and on ventilation, &c. &c. 1830. III. Hints to small holders on planting and on cattle. &c &c. 1830. IV. Irish cottagers ... 1830.

A treatise on the Irish fisheries : and various other subjects, connected with the general improvement of Ireland /

Goldsmiths'-Kress no. 22352.

Spatial overlap of grey seals and fisheries in Irish waters, some new insights using telemetry technology and VMS

Seals and humans often target the same food resource, leading to competition. This is of mounting concern with fish stocks in global decline. Grey seals were tracked from southeast Ireland, an area of mixed demersal and pelagic fisheries, and overlap with fisheries on the Celtic Shelf and Irish Sea was assessed. Overall, there was low overlap between the tagged seals and fisheries. However, when we separate active (e.g. trawls) and passive gear (e.g. nets, lines) fisheries, a different picture emerged. Overlap with active fisheries was no different from that expected under a random distribution, but overlap with passive fisheries was significantly higher. This suggests that grey seals may be targeting the same areas as passive fisheries and/or specifically targeting passive gear. There was variation in foraging areas between individual seals suggesting habitat partitioning to reduce intra-specific competition or potential individual specialisation in foraging behaviour. Our findings support other recent assertions that seal/fisheries interactions in Irish waters are an issue in inshore passive fisheries, most likely at the operational and individual level. This suggests that seal population management measures would be unjustifiable, and mitigation is best focused on minimizing interactions at nets.

Bycatch of crustacean and fish bottom trawl fisheries from southern Portugal (Algarve)

As part of two research projects for analysing bycatch and discards, we quantified catch composition, catch rates, bycatch and discard,, in two important commercial bottom trawl fisheries (crustacean and fish trawls) off the Southern coast of Portugal (Algarve). Stratified sampling by onboard observers took place from February 1999 to March 2001 and data were collected from 165 tows during 52 fishing trips. Commercial tat-get species included crustaceans: blue and red shrimp (Aristeus antennatus), deep-water rose shrimp (Parapenaeus longirostris), Norway lobster (Nepharops norvegicus); and fishes: scabreams (Diplodus spl). and Pagellus Spp.), horse Mackerels (Trachurus spp.) and European hake (Merluccius merluccius). The trawl fisheries are characterised by considerable amounts of bycatch: 59.5% and 80.4% of the overall total catch for crustacean and fish trawlers respectively. A total of 255 species were identified, which belonged to 15 classes of organisms ( 137 vertebrates, 112 invertebrates and algae). Crustacean trawlers had higher bycatch biodiversity. Bony fish (45.6% and 37.8%) followed by crustaceans (14.6% and 11.5%) were the dominant bycatch components of both crustacean and fish trawlers respectively. The influence of a number of factors (e.g. depth, fishing gear, tow duration and season) on bycatch and discards is discussed.

Development of a responsive fisheries management system for the Portuguese crustacean bottom trawl fishery: Lessons learnt

A prototype for a Responsive Fisheries Management System (RFMS) was developed in the context of the European FP7 project EcoFishMan and tested on the Portuguese crustacean trawl fishery. Building on Results Based Management principles, RFMS involves the definition of specific and measurable objectives for a fishery by the relevant authorities but allows resource users the freedom to find ways to achieve the objectives and to provide adequate documentation. Taking into account the main goals of the new Common Fisheries Policy, such as sustainable utilization of the resources, end of discards and unwanted catches, a management plan for the Portuguese crustacean trawl fishery was developed in cooperation with the fishing industry, following the process and design laid out in the RFMS concept. The plan considers biological, social and economic goals and assigns a responsibility for increased data collection to the resource users. The performance of the plan with regard to selected indicators was evaluated through simulations. In this paper the process towards a RFMS is described and the lessons learnt from the interaction with stakeholders in the development of an alternative management plan are discussed. (C) 2014 Elsevier Ltd. All rights reserved.

Alternative codends to reduce bycatch in Chilean crustacean trawl fisheries

This study was conducted to determine the reduction in bycatch and the loss of target catch in trawl hauls for three commercial crustacean species (yellow squat lobster, Cervimunida johni, nylon shrimp, Heterocarpus reedi, and red squat lobster, Pleuroncodes monodon) in central Chile. Two experiments were carried out using the covered codend method; the first used different mesh sizes (56 and 70 mm, knot-centre to knot-centre) and shapes (diamond and square), and the second tested different reduction devices (escape panel and sorting grid). We analysed the escape proportions of the species caught and the size frequency distributions of the target species and Chilean hake (Merluccius gayi), the main commercial bycatch species. The results demonstrate that it is feasible to significantly reduce bycatch while keeping losses within acceptable ranges. In particular, the best option for yellow squat lobster was the combination of a 70-mm diamond mesh with an escape panel that reduced non-target and target catches by 48% and 7%, respectively. For nylon shrimp, the best option was the use of a 56-mm diamond mesh with a sorting grid that reduced non-target and target catches by 41% and 11%, respectively. Although the results for red squat lobster were not as promising, they will help to guide future research.

Population genetic structure of brown crab (Cancer pagurus) in Irish waters

The brown crab (Cancer pagurus) fishery in Ireland is one of the most important financially and socio-economically, with the species worth approximately €15m per year in the first half of the decade. Only mackerel (Scomber scombrus) and Dublin Bay prawn (Nephrops norvegicus) are of greater value. Despite this, very little research has been conducted to describe the stock structure of brown crab on a national scale. In this study a country-wide assessment of genetic population structure was carried out. Sampling was conducted from commercial fishing boats from 11/06 to 04/08 at seven sample sites representing the central Irish brown crab fisheries, with one sample site from the UK also included in the study. Six microsatellite markers, specifically developed for brown crab, were used to assess genetic diversity and estimate population differentiation parameters. Significant genetic structuring was found using F-statistics (Fst = 0.007) and exact tests, but not with Bayesian methods. Samples from the UK and Wexford were found to be genetically distinct from all other populations. Three northern populations from Malm Head and Stanton Bank were genetically similar with Fst estimates suggesting connectivity between them. Also, Stanton Bank, again on the basis of Fst estimates, appeared to be connected to populations down the west coast of Ireland, as far south as Kerry. Two Galway samples, one inside and one outside of Galway Bay, were genetically differentiated despite their close geographic proximity. It is hypothesised that a persistent northerly summer current could transport pelagic larvae from populations along the southwest and west coasts of Ireland towards Stanton Bank in the North, resulting in the apparent connectivity observed in this study.

An assessment of biological and population parameters of the Common whelk, Buccinum undatum (L.) in the region of the North West Irish whelk fishery

The Common whelk, Buccinum undatum (L.) is a conspicuous benthic scavenger in Irish waters, and is a valuable fisheries resource in South East Ireland. B. undatum is fished in many parts of its range, and previous studies have shown that certain life history parameters, which vary with location, make this species vulnerable to overexploitation. This makes research into each exploited stock essential to ensure sustainable fisheries management of the species. In 2003, interest in B. undatum as a complementary species in the inshore fishery east of the Inishowen Peninsula, North West Ireland, initiated investigation into fisheries related biological and population aspects of the species in this region. The current study presents estimates of spatial variation and density of the stock, size at age and growth rates, size and age at onset of sexual maturity, and timing of reproductive events in the region of the North West Irish whelk fishery for the period of June 2003 to May 2004. Analysis of variance of the total shell length of whelk landings to the fishery was conducted over spatial scales of fishing pot, fishing string and landings to vessels. Landings varied significantly in shell length at the spatial scale at which whelks are attracted to baited pots, but did not vary significantly over larger spatial scales. Depletion estimates of stock density from fisheries derived Catch per Unit Effort data and a mark re-capture experiment estimate 0.134 - 0.227 whelks per m2. Two independent methods of age determination found similar growth logistics functions for B. undatum.Modal analysis of length frequency distribution of landings to the fishery estimated symptotic length, Leo = 151.64 mm and Brody growth coefficient, K = 0.04. Analysis of the striae in individual opercula, where each stria was found to represent annual growth, estimated Loo = 137.73 mm and K = 0.12. Common whelks in the region of the North West Irish whelk fishery grow slowly and are long-lived, with 19 opercula striae recorded in one individual. Onset of sexual maturity is late, and no sex-specific differences in size or age at maturity were determined in the present study. Males were found to achieve sexual maturity at 83.30 ± 10.77 mm, and 8.9 - 11.1 years of age, and females at 82.62 ± 10.68 mm and 8.8 to 11.1 years of age. Systematic observations of reproductive events, including histological changes to the female ovary and male testis, and changes in the size and mass of body components, suggest that breeding occurred between the autumn and winter months of October and December 2003. Biological aspects of B. undatum in the study region are compared with previous studies from other regions, and discussed in relation to sustainable management of the fishery.

Ireland’s understudied flatfish: reproduction, age and growth of the dab Limanda limanda (L.) in Irish coastal waters

In Ireland, although flatfish form a valuable fishery, little is known about the smallest, the dab Limanda limanda. In this study, a variety of parameters of reproductive development, including ovarian phase description, gonadosomatic index (GSI), hepatosomatic index (HSI), relative condition (Kn) and oocyte size were analysed to provide information on the dab’s reproductive cycle and spawning periods. Sampling were collected monthly over an 18-month period using bottom trawls of the Irish coastline. A six phase macroscopic guide was developed for both sexes of dab, and verified using histology. In comparisons of macroscopic and microscopic phases, there was high agreement in the proposed female guide (86%), with males demonstratively lower (62%). No significant bias was observed between the the two reproductive methods. When the male macroscopic guide was examined, misclassification was high in phase 5 and phase 5 (41%), with 96% of misclassification occurring in adjacent phases. The sampled population was primarily composed of females, with ratios of females to males 1:0.6, although the predominance of females was less noticeable during the reproductive season. Oocyte growth in dab follows asynchronous development, and spawn over a protracted period indicating a batch spawning strategy. Spawning occurred mainly in early spring, with total regeneration of gonads by May. The length at which 50% of the population was reproductively mature was identified as 14cm and 17cm, for male and female dab, respectively. Precision and bias in age determinations using whole otoliths to age dab was investigated using six age readers from various institutions. Low levels of precision were obtained (CV: 10-23%) inferring the need for an alternative methodology. Precision and bias was influence by the level of experience of the reader, with ageing error attributed to interpretative differences and difficulty in edge determination. Sectioned otolith age determinations were subsequently compared to whole otolith age determinations using two age readers experienced in dab ageing. Although increased precision was observed in whole otoliths from previous estimates (CV=0%, 0% APE), sectioned otoliths were used for growth models. This was based on multinominal logistic regression on age length keys developed using both ageing methods. Biological data (length and age) for both sexes was applied to four growth models, where the Akaike criterion and Multi model Inference indicated the logistic model as having the best fit to the collected data. In general, female dab attained a longer length then males, with growth rates significantly different between the two sexes. Length weight relationships between the two sexes were also significantly different.

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.