Defining habitat characteristics influencing the distribution, density and growth of Plaice (Pleuronectes Platessa) and Dab (Limanda Limanda) on west of Ireland nursery grounds

Plaice (Pleuronectes platessa, L.) and dab (Limanda limanda, L.) are among the most abundant flatfishes in the north-eastern Atlantic region and the dominant species in shallow coastal nursery grounds. With increasing pressures on commercial flatfish stocks in combination with changing coastal environments, better knowledge of population dynamics during all life stages is needed to evaluate variability in year-class strength and recruitment to the fishery. The aim of this research was to investigate the complex interplay of biotic and abiotic habitat components influencing the distribution, density and growth of plaice and dab during the vulnerable juvenile life stage and to gain insight in spatial and temporal differences in nursery habitat quality along the west coast of Ireland. Intraspecific variability in plaice diet was observed at different spatial scales and showed a link with condition, recent growth and morphology. This highlights the effect of food availability on habitat quality and the need to consider small scale variation when attempting to link habitat quality to feeding, growth and condition of juvenile flatfish. There was evidence of trophic, spatial and temporal resource partitioning between juvenile plaice and dab allowing the co-existence of morphologically similar species in nursery grounds. In the limited survey years there was no evidence that the carrying capacity of the studied nursery grounds was reached but spatial and interannual variations in fish growth indicated fluctuating environments in terms of food availability, predator densities, sediment features and physico-chemical conditions. Predation was the most important factor affecting habitat quality for juvenile plaice and dab with crab densities negatively correlated to fish condition whereas shrimp densities were negatively associated with densities of small-sized juveniles in spring. A comparison of proxies for fish growth showed the advantage of Fulton’s K for routine use whereas RNA:DNA ratios proved less powerful when short-term environmental fluctuations are lacking. This study illustrated how distinct sets of habitat features can drive spatial variation in density and condition of juvenile flatfish highlighting the value of studying both variables when modeling habitat requirements. The habitat models generated in this study also provide a powerful tool to predict potential climate and anthropogenic impacts on the distribution and condition of juveniles in flatfish nurseries. The need for effective coastal zone management was emphasized to ensure a sustainable use of coastal resources and successful flatfish recruitment to the fishery.

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.

The design and development of heat extraction technologies for the utilisation of compost thermal energy

A composting Heat Extraction Unit (HEU) was designed to utilise waste heat from decaying organic matter for a variety of heating application The aim was to construct an insulated small scale, sealed, organic matter filled container. In this vessel a process fluid within embedded pipes would absorb thermal energy from the hot compost and transport it to an external heat exchanger. Experiments were conducted on the constituent parts and the final design comprised of a 2046 litre container insulated with polyurethane foam and kingspan with two arrays of qualpex piping embedded in the compost to extract heat. The thermal energy was used in horticultural trials by heating polytunnels using a radiator system during a winter/spring period. The compost derived energy was compared with conventional and renewable energy in the form of an electric fan heater and solar panel. The compost derived energy was able to raise polytunnel temperatures to 2-3°C above the control, with the solar panel contributing no thermal energy during the winter trial and the electric heater the most efficient maintaining temperature at its preset temperature of 10°C. Plants that were cultivated as performance indicators showed no significant difference in growth rates between the heat sources. A follow on experiment conducted using special growing mats for distributing compost thermal energy directly under the plants (Radish, Cabbage, Spinach and Lettuce) displayed more successful growth patterns than those in the control. The compost HEU was also used for more traditional space heating and hot water heating applications. A test space was successfully heated over two trials with varying insulation levels. Maximum internal temperature increases of 7°C and 13°C were recorded for building U-values of 1.6 and 0.53 W/m2K respectively using the HEU. The HEU successfully heated a 60 litre hot water cylinder for 32 days with maximum water temperature increases of 36.5°C recorded. Total energy recovered from the 435 Kg of compost within the HEU during the polytunnel growth trial was 76 kWh which is 3 kWh/day for the 25 days when the HEU was activated. With a mean coefficient of performance level of 6.8 calculated for the HEU the technology is energy efficient. Therefore the compost HEU developed here could be a useful renewable energy technology particularly for small scale rural dwellers and growers with access to significant quantities of organic matter

Development of a data acquisition system to characterise sustainable energy technologies and to support Web-Based learning (DAQ-WBL)

Driven by concerns about rising energy costs, security of supply and climate change a new wave of Sustainable Energy Technologies (SET’s) have been embraced by the Irish consumer. Such systems as solar collectors, heat pumps and biomass boilers have become common due to government backed financial incentives and revisions of the building regulations. However, there is a deficit of knowledge and understanding of how these technologies operate and perform under Ireland’s maritime climate. This AQ-WBL project was designed to address both these needs by developing a Data Acquisition (DAQ) system to monitor the performance of such technologies and a web-based learning environment to disseminate performance characteristics and supplementary information about these systems. A DAQ system consisting of 108 sensors was developed as part of Galway-Mayo Institute of Technology’s (GMIT’s) Centre for the Integration of Sustainable EnergyTechnologies (CiSET) in an effort to benchmark the performance of solar thermal collectors and Ground Source Heat Pumps (GSHP’s) under Irish maritime climate, research new methods of integrating these systems within the built environment and raise awareness of SET’s. It has operated reliably for over 2 years and has acquired over 25 million data points. Raising awareness of these SET’s is carried out through the dissemination of the performance data through an online learning environment. A learning environment was created to provide different user groups with a basic understanding of a SET’s with the support of performance data, through a novel 5 step learning process and two examples were developed for the solar thermal collectors and the weather station which can be viewed at http://www.kdp 1 .aquaculture.ie/index.aspx. This online learning environment has been demonstrated to and well received by different groups of GMIT’s undergraduate students and plans have been made to develop it further to support education, awareness, research and regional development.