ICES Journal of Marine Science: Journal du Conseil

Glass, Christopher W.; Walsh, Stephen J.; van Marlen, Bob

doi: 10.1093/icesjms/fsm139pmid: N/A

Reid, D. G.; Allen, V. J.; Bova, D. J.; Jones, E. G.; Kynoch, R. J.; Peach, K. J.; Fernandes, P. G.; Turrell, W. R.

doi: 10.1093/icesjms/fsm106pmid: N/A

Reid, D. G., Allen, V. J., Bova, D. J., Jones, E. G., Kynoch, R. J., Peach, K. J., Fernandes, P. G., and Turrell, W. R. 2007. Anglerfish catchability for swept-area abundance estimates in a new survey trawl. ICES Journal of Marine Science, 64: 15031511.In 2005, a new trawl survey was launched in Scotland to estimate anglerfish (Lophius spp.) abundance using swept-area estimates. This required an understanding of the herding of the fish by the gear, particularly in the zone between the doors and wing ends. TV observations at the wing ends and along the sweeps were used to quantify the behavioural reactions of anglerfish. These observations were analysed to develop a gear efficiency estimate. This paper details the construction of the net and the procedures for data collection on the survey. In all, 54 reliable observations of anglerfish were recorded at the groundgear, the wing ends, and along the sweep/bridle combination. Detailed analysis of the recordings showed that all fish in the path of the net were captured, whereas more than half of the fish between the wings and the doors were not. The fish did not appear to herd and many of the encounters with the wires were passive. An individual-based particle-tracking model was constructed to use the behavioural observations to simulate the capture process and generate an efficiency factor. The calculated efficiency factor, based on the behavioural observations, was 1.04, indicating that almost all fish encountering the sweeps and bridles were lost. The implications and suggestions for development of this work are discussed.

Rotherham, D.; Underwood, A. J.; Chapman, M. G.; Gray, C. A.

doi: 10.1093/icesjms/fsm096pmid: N/A

Rotherham, D., Underwood, A. J., Chapman, M. G., and Gray, C. A. 2007. A strategy for developing scientific sampling tools for fishery-independent surveys of estuarine fish in New South Wales, Australia. ICES Journal of Marine Science, 64: 15121516.The limitations of using fishery-dependent data, i.e. from commercial and recreational fisheries to assess harvested stocks of fish and invertebrates, are well known. Increasingly, fishery-independent surveys are used to validate data from fishery-dependent sources and to provide indices of recruitment and broader ecological information about species not normally retained in fishing operations. Any large-scale, long-term, fishery-independent study must develop sampling gear and designs that are standardized, representative, optimal with respect to the quantity and structure of catch, and replicated over relevant spatial and temporal scales. We present a strategy for achieving appropriate sampling designs. This involves: (i) identifying suitable sampling gears for target species; (ii) testing different configurations of gear and sampling practices to ensure that samples are optimal, representative, and cost efficient; (iii) understanding scales of spatial and temporal variability; and (iv) costbenefit analyses to optimize replication. Examples of this strategy are illustrated, with brief considerations of the values of pilot research in developing fishery-independent sampling.

Takagi, Tsutomu; Shimizu, Takashi; Korte, Holger

doi: 10.1093/icesjms/fsm097pmid: N/A

Takagi, T., Shimizu, T., and Korte, H. 2007. Evaluating the impact of gillnet ghost fishing using a computational analysis of the geometry of fishing gear. ICES Journal of Marine Science, 64: 15171524.We developed a net shape and load analysis system (NaLA) that can estimate the three-dimensional shape of fishing gear underwater computationally. This paper introduces the latest version of the numerical model of the NaLA. Previously, NaLA was used to estimate the net geometries and internal forces of some fishing gear, demonstrating its general versatility. However, the ultimate goal of our study has been to learn about the impact of fishing and the capture process from a physical perspective, not simply to develop elemental technologies for gear design. Accurate, quantitative evaluation of fishing gear performance from a physical perspective can be used to estimate the potentialities of the ghost fishing to gillnet gears. Although the applications are not limited to geometries and internal forces, the paper describes how computer-aided simulations of fishing gear should be applied to investigations of the impact of ghost fishing caused by lost drift and bottom gillnets. The computational results showed that a driftnet with homogenous net panels was deformed slightly and bent only at the two ends of the net. Accumulation of periphyton on a bottom gillnet after 25 d of immersion caused it to settle to the sea bottom.

Jennings, Simon; Revill, Andrew S.

doi: 10.1093/icesjms/fsm104pmid: N/A

Jennings, S., and Revill, A. S. 2007. The role of gear technologists in supporting an ecosystem approach to fisheries. ICES Journal of Marine Science, 64: 15251534.Central to an ecosystem approach to fisheries (EAF) is reconciling the short-term need for catches with the long-term need for sustainability of target species and other ecosystem components. We assess the role of gear technology in supporting the objectives and implementation of EAF and identify the circumstances in which investment in the environmental performance of fishing gear provides the greatest benefits. The greatest benefits are usually achieved when gear technologists embed the new technology in the management system and when there are clear incentives to use it. We propose a framework for comparing combinations of management measures that might support EAF, based on knowledge of the environmental impacts of different gears in different areas and management systems. This framework helps us assess when fishing effects matter and when gear technologists should contribute to mitigating unwanted effects. Incentives and effective enforcement will be key to introducing gears with lower environmental impact. We expect that future emphasis on marine spatial planning, the use of environmental impact assessment and strategic environmental assessment for fisheries, more equitable treatment of fisheries and other marine sectors, and rising oil prices will lead to greater pressure on gear technologists to support EAF.

Davis, M. W.

doi: 10.1093/icesjms/fsm087pmid: N/A

Davis, M. W. 2007. Simulated fishing experiments for predicting delayed mortality rates using reflex impairment in restrained fish. ICES Journal of Marine Science, 64: 15351542.Development of efficient methods to predict discard and escapee mortality in fishing operations is essential to the conservation of sensitive fish stocks. For a few fisheries, mortality data are available from fishing experiments in the field; these require long-term holding or monitoring of fish in tanks, cages, or tag and recapture experiments to detect delayed mortality. A different approach to predicting discard and escapee mortality is to use reflex action mortality predictors (RAMP) consisting of relationships between mortality and reflex impairment for species of interest. Fish were towed in a net in the laboratory and then either restrained in foam-lined holders and rapidly tested for reflex impairment five minutes after towing, or held for up to 60 days to determine delayed mortality. Delayed mortality occurred up to 20 days after towing. RAMP was related to mortality with biphasic sigmoid functions. As fishing stressors increased in intensity, the first phase showed an increase in RAMP with no concomitant mortality. In the second phase, RAMP continued to increase, while mortality became apparent and increased. The measurement of RAMP in restrained fish on board fishing vessels during experiments to predict discard mortality and in caged free swimming fish to predict escapee mortality is feasible and advisable.

Ferro, R. S. T.; Jones, E. G.; Kynoch, R. J.; Fryer, R. J.; Buckett, B-E.

doi: 10.1093/icesjms/fsm099pmid: N/A

Ferro, R. S. T., Jones, E. G., Kynoch, R. J., Fryer, R. J., and Buckett, B-E. 2007. Separating species using a horizontal panel in the Scottish North Sea whitefish trawl fishery. ICES Journal of Marine Science, 64: 15431550.In the North Sea, Scottish vessels target haddock, cod, whiting, monkfish, saithe, and flatfish in a mixed whitefish trawl fishery. These species mature at different sizes and hence have a range of minimum landing sizes. Their different shapes and swimming capabilities imply different selection characteristics when escaping from trawl gear. However, they are often caught at the same time on the same grounds. Optimal exploitation can only be achieved by ensuring that the selection of each species varies appropriately with length during the fishing process. This paper describes one part of a large European project to develop species-selective trawl gear to improve the exploitation pattern of North Sea cod, while maintaining the catch of other important commercial species. A gear suitable to the Scottish mixed whitefish fishery was fitted with a horizontal panel in the tapered part of the net to separate species into an upper and lower compartment. Trials were conducted on research vessels to measure separation performance for nine species in different light conditions, at different towing speeds, and with different lengths of panel. Most haddock, whiting, and saithe pass above the panel, whereas most cod, flatfish, and monkfish pass below it. Towing speed and panel length had no significant effect on separation. At lower light levels during the night (April at latitude 58 to 61N), fewer dab, sole, plaice, and cod pass below the panel. Observations and measurements of fish behaviour using acoustic methods are described. They suggest that the height at which fish enter the net mouth may be influenced by light level and water clarity.

He, Pingguo; Balzano, Vincent

doi: 10.1093/icesjms/fsm098pmid: N/A

He, P., and Balzano, V. 2007. Reducing the catch of small shrimps in the Gulf of Maine pink shrimp fishery with a size-sorting grid device. ICES Journal of Marine Science, 64: 15511557.Since implementation of the Nordmre grid in the Gulf of Maine pink shrimp (Pandalus borealis) trawl fishery in the early 1990s, fish bycatch has been reduced drastically. However, the Nordmre grid does not reduce the amount of small shrimps landed when the shrimps are on the fishing grounds. This paper reports on two designs of a new size-sorting grid system, one with a funnel and one without. The designs' main feature is the size-sorting grid's position, installed in front of the main Nordmre grid. They were tested in the flume tank and at sea. Parallel tows involving two vessels and alternating tows using one vessel were made to compare the size-sorting grid system. Both size-sorting designs reduced the number of small shrimps in the catch significantly, by 38 and 45 kg1 of catch, respectively. There was some reduction in shrimp catch rates, presumably from the release of small shrimps. There were no significant differences in the number or quantity of major bycatch species for the commercial grid and the two experimental grid designs. The designs were practical to operate and easy to install. Their application could reduce the catch of small shrimps in the pink shrimp fishery in the Gulf of Maine and in other areas.

O'Neill, F. G.; Herrmann, B.

doi: 10.1093/icesjms/fsm101pmid: N/A

O'Neill, F. G., and Herrmann, B. 2007. PRESEMOa predictive model of codend selectivitya tool for fishery managers. ICES Journal of Marine Science, 64: 15581568.The codend selectivity simulation model PRESEMO is a predictive model based on an understanding of the physical, biological, and behavioural mechanisms that underpin codend selection. In this paper, PRESEMO is used to predict the selectivity of a large range of codends of varying design. In particular, the selectivity of codends with mesh sizes in the range 80160 mm, number of meshes around in the range 60140, and netting twine thickness in the range 36 mm are predicted and, where possible, the predictions are validated with experimental data. Using the simulated data, the codend selectivity parameters are expressed in terms of the gear design parameters and in terms of both catch size and gear design parameters. The potential use of these results in a management context and for the development of more selective gears is highlighted by plotting iso-l50 and iso-sr curves used to identify gear design parameters that give equal estimates of the 50 retention length and the selection range, respectively. It is emphasized that this approach can be extended to consider the influence of other design parameters and, if sufficient relevant quantitative information exists, biological and behavioural parameters. As such, the model presented here will provide a better understanding of the selection process, permit a more targeted approach to codend selectivity experiments, and assist fishery managers to assess the impact of proposed technical measures that are introduced to reduce the catch of undersized fish and unwanted bycatch.

zbilgin, Hseyin; Tosunolu, Zafer; Toka, Adnan; Metin, Glnur

doi: 10.1093/icesjms/fsm115pmid: N/A

zbilgin, H., Tosunolu, Z., Toka, A., and Metin, G. 2007. Seasonal variation in the trawl codend selectivity of picarel (Spicare smaris). ICES Journal of Marine Science, 64: 15691572.Seasonal selectivity of commercial 40 mm polyethylene codend was tested for picarel (Spicara smaris) in spring (418 April 2002), summer (1025 July 2002), autumn (26 September2 October 2002), and winter (2223 January 2003) in the Aegean Sea. Data were collected using the covered codend technique and analysed using the logistic equation with the maximum likelihood method. Four sets of selection curves were analysed and compared using the model developed by Fryer (1991). Highest L50 is in autumn (13.82 cm; s.e. 0.62), when water temperature is highest and the fish are expected to be in their best condition after summer feeding. Lowest L50 is in spring (11.09 cm; s.e. 0.51), when water temperature is lowest and the fish are at their spawning stage. However, there is not sufficient evidence to say that the seasonal variation in the selectivity of 40 mm polyethylene codend for picarel is statistically significant (p > 0.05).