Marine Science & Technology

The common whelk, Buccinum undatum, was sampled from three areas; east and west Shetland, and the south coast of England. The largest whelk measured 122 mm shell length (SL) and was recorded from west Shetland (mean 76 mm) with the smallest animal recorded from south England, measuring 31 mm (mean 54 mm). Both east and south areas showed a peak in length-frequency distributions greater than the minimum landing size (MLS). The peak in the west was found below the MLS, which was the only site to show a bimodal length-frequency distribution. Fisheries recruitment was estimated to occur at 6 years of age for east, 7 for west, and 4 for south regions using estimates from von Bertalanffy growth curves. Imposex was not found to be prevalent in Shetland. Significant differences were noted between east and west Shetland, and between Shetland and south England, for all measured parameters of: SL, growth, age, flesh weight, and individual yield. These results suggest that a large-scale MLS for B. undatum is not practical when local fisheries are in differing states of maturity, as seen in Shetland and south England, and that micro-management within the fishery should be considered on a region by region basis to assess the practicality of such a management measure.

Trials were carried out to evaluate the effects of a square mesh panel on the catches of a demersal trawl during normal commercial fishing operations over a period of 1 year. A 100 mm cod-end fitted with a 90 mm mesh square mesh panel between 6.3 and 9.3 m from the cod-line was compared with an identical cod-end with no panel, attached to the same net, using the alternate haul method. The square mesh panel significantly reduced the catch of undersized whiting (by an estimated 34%; p < 0.001) and of whiting greater than the minimum landing size up to lengths of about 32 cm (p < 0.05). However, the square mesh panel had no significant effect on the catches of haddock, cod or monkfish. Hauls with a small-mesh cod-end showed that large numbers of small haddock were present in the areas where the trials were carried out. Few of these fish were retained by the normal cod-end, either with or without the square-mesh panel, suggesting that fitting the square mesh panel did not appreciably improve the selectivity of the cod-end design used in these trials.

Automated handlining (jig fishing) has recently been trialled in waters around Shetland, UK. Although different types and colours of artificial lures are commercially available there is a paucity of information available on the effects of either lure design or lure colour on resulting catches. We compared the catch rates of (1) five colours of rubber eel tube lures; and (2) five different designs of artificial lure commonly used in handline fisheries. Lure colour did not significantly affect catches of pollack (Pollachius pollachius), saithe (Pollachius virens), cod (Gadus morhua), ling (Molva molva) or tusk (Brosme brosme). Cod showed a preference for lower hooks on the six hooks per reel setup when lures were black and pollack showed a preference for lower hooks when the lures were blue. There were no significant differences in catches of saithe, cod, ling or tusk between the five lure types. However, catches of pollack on a novel 'sonar' lure were lower than on other lures. No evidence of a preference for any hook position on the reels was found with any of the lure types.

Movement and growth of Lophius piscatorius were investigated around the Shetland Islands, UK, in a tagging study when a total of 1768 trawl caught fish was tagged using conventional dart tags and released on inshore fishing grounds during the autumn of 2000 and the summer of 2001. This is the first tagging study to have been undertaken on the species in UK waters and for the first time provides actual growth data for the northern monkfish stock. Monkfish of between 25 and 83 cm total length were tagged. The overall recapture rate was 4.5% and times at liberty ranged from 5 to 1078 days. Recapture positions of 35% of individuals were less than 25 km from the release positions, with some recaptures close to release positions after periods of more than 1 year. Recapture locations of some individuals indicated movements between inshore grounds. During the late autumn and winter recapture locations suggested that a general offshore migration towards the shelf edge had occurred. The largest displacement recorded was 876 km with movement being from the release location at Shetland to a fishing ground at the south east of Iceland, another recapture occurred close to Faroe. This suggests that these individuals had crossed the Faroe-Shetland Channel. This is of particular importance as it may indicate a wider mixing of stocks. Growth of recaptured fish averaged 9.4 cm year −1 .

Dobby, H., Allan, L., Harding, M., Laurenson, C. H., and McLay, H. A. 2008. Improving the quality of information on Scottish anglerfish fisheries: making use of fishers’ data. – ICES Journal of Marine Science, 65: 1334–1345. In recent years, the International Council for the Exploration of the Sea (ICES) Working Group on the Assessment of Northern Shelf Demersal Stocks has been unable to provide an analytical assessment for anglerfish. One of the reasons for this has been the poor quality of the commercial catch-and-effort data, with ICES and the European Commission’s Scientific, Technical, and Economic Committee for Fisheries (STECF) stressing the need for reliable information on which to base estimates of stock status. In response, and following consultation with the fishing industry, an anglerfish tallybook project was implemented in Scotland as part of a long-term approach to providing better data. Tallybooks are completed on a haul-by-haul basis. Skippers record catches of angl...

Laurenson, C. H., Dobby, H., and McLay, H. A. 2008. The Lophius budegassa component of monkfish catches in Scottish waters. – ICES Journal of Marine Science, 65: 1346–1349. To date, research efforts on Lophius species in waters around Scotland (ICES Divisions IVa, VIa, and VIb) have focused almost exclusively on Lophius piscatorius. Here, the characteristics and distribution of the Lophius budegassa component of the catch are described using data collected by observers during commercial fishing trips and scientific surveys on chartered commercial fishing vessels between 1998 and 2006. At Rockall Bank (VIb), L. budegassa were rare, just 0.1% of the catch of Lophius spp., whereas west of Scotland (VIa) and around the Shetland Islands (IVa), they made up 18 and 2% of catches, respectively, with greatest prevalence towards the shelf edge. Fish length ranged from 16 to 89 cm with a modal length at 40 cm. Greater proportions of large individuals were recorded around the Shetland Islands t...

Laurenson, C. H., Dobby, H., McLay, H. A., and Leslie, B. 2008. Biological features of the Lophius piscatorius catch in Scottish waters. – ICES Journal of Marine Science, 65: 1281–1290. Here, data on 50 265 Lophius piscatorius sampled between 1998 and 2006 on board commercial fishing vessels during observer trips and chartered surveys at Shetland, west of Scotland, and Rockall are analysed. In each area, length differed significantly with depth (p &lt; 0.001), there was an increase in modal size with increasing depth down to 450 m, and large fish dominated hauls in deeper water. The sex ratio of all data combined was 0.88 females:1 male, but it varied by area, depth, and season, with males greatly outnumbering females in deep water west of Scotland during the first quarter of the year. The proportion at length that were female differed significantly with depth, and the highest proportions of mature fish were in deep water at Rockall and west of Scotland. L50% maturities, for all dat...

The diet of anglerfish (Lophius piscatorius), based on the analysis of stomach contents, was investigated in the Shetland Islands. Samples were obtained during trawling for sandeel (Ammodytidae species) and demersal trawling when mainly whitefish (gadoids) are targeted. This allowed the diets of samples collected from different areas and at different times to be compared. The diets in different length groups were also compared and niche breadth investigated.A wide range of prey types, mainly fish, were recorded but the main prey was Norway pout (Trisopterus esmarkii) and lesser sandeel (Ammodytes marinus). Diet composition varied seasonally. In samples collected during whitefish trawling the occurrence of empty stomachs decreased from the first to the third quarters and generally increased with increasing anglerfish size. Empty stomachs occurred less frequently in samples collected from areas where sandeel fishing occurred compared to areas where whitefish trawling occurred.

Overview of European fisheries statistical and stock assessment areas for commercially important fish species, including anglerfish. Nordic waters is defined for the purposes of this report, and comprises waters around Iceland (ICES Division Va), the Faroe Islands (Vb) and Norway (IIa), as well as Skagerrak (IIIa), and northern (IVa) and central parts of the North Sea (IVb). Northern Shelf and Southern Shelf are areas for which the ICES carries out annual anglerfish stock assessments. In the North Sea divisions Northern Shelf and Nordic waters overlap.

Automated handlining (jig fishing) has recently been trialled in waters around Shetland, UK. Although different types and colours of artificial lures are commercially available there is a paucity of information available on the effects of either lure design or lure colour on resulting catches. We compared the catch rates of (1) five colours of rubber eel tube lures; and (2) five different designs of artificial lure commonly used in handline fisheries. Lure colour did not significantly affect catches of pollack (Pollachius pollachius), saithe (Pollachius virens), cod (Gadus morhua), ling (Molva molva) or tusk (Brosme brosme). Cod showed a preference for lower hooks on the six hooks per reel setup when lures were black and pollack showed a preference for lower hooks when the lures were blue. There were no significant differences in catches of saithe, cod, ling or tusk between the five lure types. However, catches of pollack on a novel 'sonar' lure were lower than on other lures. No evidence of a preference for any hook position on the reels was found with any of the lure types.

Anglerfish in Faroese waters are exploited in Faroese gillnet and trawl fisheries. The age, growth, and reproduction of anglerfish are studied using data from 2001-2006. Age was determined by counting the growth rings in sectioned illicia, sampled from anglerfish caught by the commercial fleet and in fisheries research surveys. The gonad maturity was visually classified into five stages where stage one is immature through to stage four being ripe or spawning and stage five being spent. Female anglerfish grow larger and reach older ages than males. Significant differences between sexes were found when comparing growth in weight related to length and mean length at age for fish older than six years. Growth until maturation was around 9 cm per year and around 5 cm per year after maturation for both sexes. The conversion factor for gutted weight to round weight (g) for all sampled anglerfish was 1.27. Females had a higher conversion factor than males. Proportion of females and males analysed by length was roughly equal in the length interval up to around 60 cm, between 60-75 cm males were slightly more numerous, and over 75 cm females were predominant. Fish larger than 110 cm were all female. Length at first maturity (L 50%) was calculated to be 83 cm for females and 57 cm for males. This corresponds to an age at maturity of around eight years for females and five years for males. Gonadosomatic index (GSI) values higher than 10% were taken to indicate signs of maturation and were found in females larger than 90 cm. Male GSI increased after a length of about 55 cm, which confirms male length at first maturity. Based on observations of ripe females and GSI data, the spawning season is suggested to be in late winter and early spring. Findings of egg ribbons and pelagic anglerfish larvae, together with other observations, suggest that there is some spawning activity of anglerfish in Faroese waters. The results of the present anglerfish study are comparable with those reported from other areas of the north Atlantic.

Jig fishing, or automated handlining, was last attempted commercially in Shetland in the early 1990s. However, although the initiative was considered to be a success, the metier has not gained precedence over otter trawling. The recent difficulties encountered by the whitefish sector combined with advances in jigging machine technology indicated that an evaluation of this approach should be revisited. Jig fishing has significant economic benefits as little fuel is consumed in comparison to trawling. This reduces vessel running costs which, with current fuel prices, can also increase profit margins significantly. The aim of this study, carried out over a 15 month period, was to evaluate the commercial viability of jig fishing for whitefish around the Shetland Isles. Five hundred and sixty eight boxes of fish valued at £29,000 were caught and landed during 119 days fishing. The principal species in the catch were saithe (Pollachius virens) and pollack (Pollachius pollachius), while small quantities of cod (Gadus morhua), ling (Molva molva) and tusk (Brosme brosme) were also caught. Fuel costs while jig fishing were significantly lower than when otter trawling. Potential income combined with reduced running costs indicate that this metier has considerable potential to be successfully implemented by inshore fishermen.

A DRAM memory cell includes a cell transistor (91a) having a source/drain region (6a) connected to a lower electrode (15) of a capacitor (18a) through a pad (10a) and a storage node (11a). During a pause, the lower electrode (15) is not depleted, but at least one of the pad (10a) and the storage node (11a) is depleted to increase a voltage drop therein. The voltage drop alleviates an electric field at a gate end of the transistor (91a) to reduced a TAT (Trap Assisted Tunneling) induced leakage current. The DRAM memory cell is provided which decreases a leakage current from the capacitor and increases time intervals between refresh operations, or refresh pause time.

Commercial jig fishing, also known as automated handlining, is a method of fishing using hooks with lures which are ‘jigged’ up and down in the water. Jig fishing techniques have been used for centuries by European vessels fishing Icelandic, Newfoundland and North Sea fishing grounds. Many of the techniques used then are still in use today. In recent years however, the advent of hydraulic or electric automated jigging machines has eliminated much of the manual labour required to haul fish from great depths. Modern automated jigging machines are equipped with a computerised motor which enables the user to program the machine to suit individual requirements (Figure 1).

Here, data on 50 265 Lophius piscatorius sampled between 1998 and 2006 on board commercial fishing vessels during observer trips and chartered surveys at Shetland, west of Scotland, and Rockall are analysed. In each area, length differed significantly with depth (p, 0.001), there was an increase in modal size with increasing depth down to 450 m, and large fish dominated hauls in deeper water. The sex ratio of all data combined was 0.88 females:1 male, but it varied by area, depth, and season, with males greatly out-numbering females in deep water west of Scotland during the first quarter of the year. The proportion at length that were female differed significantly with depth, and the highest proportions of mature fish were in deep water at Rockall and west of Scotland. L50 % maturities, for all data combined, were 102.4 cm for females and 58.3 cm for males.

Fisheries data collection through industry-science partnerships have significant potential to support stock assessments and sustainable management, but few studies have described the steps taken en route to a successful partnership. This paper describes the development of the Scottish Pelagic Industry-Science Data Collection Programme; why and how it started, and what it has taken to develop a routine and consistent voluntary sampling regime of sufficient quality to become the main source of biological data on pelagic fish catches in Scotland. Using our experience, we emphasise the importance of establishing procedures that ensure the quality of methods and results, of working with institutions responsible for provision of national data, and of actively engaging with the International Council for the Exploration of the Sea (ICES) workshops and working groups on data quality, stock assessment and stakeholder engagement. The development of the programme has been, and remains to be, a mutual learning process which is reflected upon from our different institutional perspectives. The experience gained during this work has built knowledge useful for practitioners in other situations. Specifically, we identify five transferable design principles that we believe have been essential to success so far. Finally, we look at the steps ahead in our efforts toward continuous improvements.