A numerical study of a method for measuring the effective in situ sound absorption coefficient

The accuracy of a method [Wijnant et al., “Development and applica- tion of a new method for the in-situ measurement of sound absorption”, ISMA 31, Leuven, Belgium (2010).], for measurement of the effective area-averaged in situ sound absorption coefficient is investigated. Based on a local plane wave assump- tion, this method can be applied to sound fields for which a model is not available. Investigations were carried out by means of finite element simulations for a typical case. The results show that the method is a promising method for determining the effective area-averaged in situ sound absorption coefficient in complex sound fields

Growth and Survivorship of Scleractinian Coral Transplants and the Effectiveness of Plugging Core Holes in Transplant Donor Colonies

Replicate scleractinian coral transplants were obtained from the species Meandrina meandrites and Montastrea cavernosa on a natural reef, off Dania Beach, Florida, using a hydraulic drill fitted with a 4 in. (~10 cm) core barrel. The transplants were fixed to Reef Ball™ substrates using an adhesive marine epoxy. Drill holes in the donor corals (core holes) were filled with concrete plugs. Control corals, of comparable size to both donor colonies and transplant corals, were monitored for comparison. Transplant corals, donor corals, and controls on the natural reef were monitored for growth and survivorship. Core holes were monitored for tissue regrowth over the surface of concrete plugs. Growth during the transplantation project was defined as an increase in surface area of tissue and skeleton. Growth was monitored on a quarterly basis using photographic techniques. Meandrina meandrites transplants experienced greater mortality and significantly less growth than M. cavernosa transplants. No significant difference in the change in percent tissue coverage between both species of donor corals or between their respective controls was determined. The process of filling core holes in donor colonies with concrete plugs was effective, however, tissue did not completely regenerate over the surface of plugs in either species over the relatively short 15-month observation period. Results of this study indicate that species selection is an important factor in the success of coral transplantation

The spurdog Squalus acanthias (L) fishery in south west Ireland

Spurdog landings are made on all parts of the Irish coastline but most heavily concentrated on the west of the country. The fishery expanded to a maximum catch of just under 8,000 tonnes in 1985. The species had been pursued most intensively in the north west but effort is shifting southwards. This account of the south west Ireland fishery is based on material collected between April 1987 and March 1988, inclusive; information was collected by questionnaire and 5,300 individual fish were examined. Ageing was undertaken using the posterior spine: ages in the commercial catches ranged between 5 and 40+ years. The growth characteristics of the south-west Ireland spurdogs resemble those of the Scottish-Norwegian fish, but the Irish populations have a lower L∞. Female maturation takes place at a shorter length than in other populations hitherto investigated from British or Irish waters; the length at 50% maturity is slightly more than 74cm which corresponds with an age of 14 years. The fecundity of the south west Ireland spurdogs is relatively high. Mortality coefficients (Z) of fully recruited spurdogs are calculated from age 17 as 0.24 for females and 0.30 for males. Two life tables are constructed. The first, which is intended to ascertain the numbers of female whelps required to maintain numbers, suggests that the stocks are close to being overfished. The second life table examines the age structure of the breeding female component of the population but its outcome is inconclusive. In terms of its organization the south west of Ireland spurdog fishery can be considered as two separate fisheries: a trawl and a gill net fishery, the latter being regarded as the more detrimental to the prospect of sustained yield

Profile of the Caragh, County Kerry: A Salmonid Producing Catchment

From the mid 1960s competition for Atlantic salmon intensified with the expansion of high seas fisheries in the marine sub-Arctic and drift-netting closer to home. Inshore commercial fishermen and freshwater anglers saw progressively more of the salmon stock being landed outside its river of origin which prompted some to seek an alternative game species. Sea trout, which have traditionally been a by-catch of the commercial salmon fishery and which game fishermen valued, were considered and various clubs and individuals (fishery owners and managers) addressed queries to the Department responsible for fisheries on the possibility of developing a sea trout run to supplement a declining salmon population. The majority of queries examined by this writer concerned the introduction of sea trout to parts of river systems outside their normal range. A review of sea trout distribution (Fahy, 1977) described their migratory limit inland and contained adequate information to assess the suitability of the majority of fresh water bodies for the fish. The Caragh (Glencar) catchment was more intriguing. There are now in existence many investigations on the inter-relationships of salmonid species in fresh water and on their interactions with their environment but there are few specific references to the suitability of catchments for particular species. This investigation examines a case in point

Fish Kills in Ireland in 1985

Fish kills reported by the water pollution officers of the Regional Fisheries Boards in 1985 are evaluated as were similar incidents in 1983 and 1984. Trout, Salmo trutta, was the species most widely implicated and the suspected cause of death was oxygen depletion resulting from agricultural activities. The small number of kills (37), compared with other years, was attributed to weather conditions and particularly to high rainfall in 1985. Contrary to expectation, the average numbers of fish killed in an incident were higher and the channel lengths affected were twice as long as in 1983 and 1984. Whether these findings represent a new pattern of water pollution is not known

Have Hatcheries a Role in Sea-Trout Management?

The artificial propagation of sea trout in Ireland has a long history but the fish were never produced in large numbers and they were disposed of at an early stage in development. The evidence suggests that artificial propagation was undertaken as a by-product of salmon management. The circumstances in which artificial propagation of sea trout may be justified are examined and some general reservations are expressed. For the future it seems likely that sea trout will be exploited in wild rather than in put-and-take fisheries. The emphasis should remain on providing the most suitable nursery conditions for the fish to reproduce naturally. Further investigations should however be undertaken on devising suitable methods of propagating sea trout and consideration might be given to re-establishing some of the long lived strains which are now believed to be extinct

Sea Trout from the Currane Fishery in 1973 and 1974

Collections of 1,163 sets of scales from rod-caught sea trout Salma trutta L., made in 1973 and 1974, are described and the results compared with data from previous collections. The mean weight of 821 g was higher than usual in Irish fisheries and smolts were large, ranging from 22.8 to 24.5 cm at two years. Previous indications of a long lived-stock were confirmed by the identification of 37 age categories. The amount of B type growth was considerably less than that observed in samples from rivers with longer estuaries. Marine growth was relatively poor so that the length attained at the end of each sea winter was similar to that of sea trout in other Irish populations. The large size of specimens in the Waterville fishery may therefore be ascribed to longevity rather than to rapid growth at sea. Circuli on parr scales were more numerous than on scales from an east coast sample. Changes observed since the 1944 sampling included an increase in the proportion of older fish indicating that the drift net fishery has not had an adverse effect on the stocks

Fisheries for Ray (Batoidei) in Western statistical area viia, investigated through the commercial catches.

The status of the Irish Sea ray fishery is investigated using commercial catches of rays landed into two ports, Howth and Arklow. Approximately 80 45kg boxes were examined monthly over a year when approximately 100 individuals of each of the four contributing species were aged and measured. The species are R. naevus, montagui, clavata and brachyura. These are inter-mixed and casually segregated into four grades on their length. Weighting factors are provided to raise the sampled numbers to total landings. The frequency distribution of grades at the two ports is established from an analysis of some 5,700 commercial transactions. At Arklow, the pattern is stable from one year to another and apparently seasonal. Arklow boats have a short range. The pattern of landings at Howth is more complex; these vessels have a longer range and probably exploit various ages of rays. Growth in all four species occurs most actively during the summer months, slowing down in the winter. Annulus formation is not readily associated with the conventional birth date of 1 January. Coefficients of total mortality (Z) are high for the four species (0.38-1.00), higher than those found in a recent study of rays in Carmarthen Bay. R. brachyura is the most valuable species. R. naevus is the most numerous, possibly because it has a competitive advantage due to its age at full recruitment being one year later than those of the other three species. The yield of rays increases moving offshore and in a southerly direction in the Irish Sea. Landings into Irish ports by Irish vessels have increased between 1903 and 1985 although, until recently, ray as a percentage of total demersal landings was declining, from the 1950s

The Maharees spider crab Maja squinado fishery in 2000

A pot fishery directed on spider crab (Maja squinado) grew out of a mixed tangle net and pot fishery for large crustaceans in the early 1980s. Approximately twenty half decked vessels of 10m in length have been involved for the duration of the fishery but the numbers of pots per vessel has increased; currently 10,000 pots are set for spider crab in Tralee and Brandon Bays during the summer months. Cpue rose initially during the early years of the fishery, then it stabilised and declined although in the late 1990s it again recovered somewhat. Sampling in 2000 suggests that the size composition of the catch has altered since the early years of the fishery, its main consequence being the removal of the older age groups so that the landings now consist almost entirely of a single year class. Aspects of the biology of the Maja squinado are compared with what is already known of the species and a number of recommendations are made for the future management of the fishery. These include a further increase in the size limit, a ban on tangle nets and a cap on fishing effort.Funder: Marine Institut