Lee Murray - Academia.edu (original) (raw)

Papers by Lee Murray

This report examines the likely impacts on the scallop fishing fleet of management measures propo... more This report examines the likely impacts on the scallop fishing fleet of management measures proposed for the 2014 queen scallop fishing season. The imposition of a maximum vessel length of 15 m LOA in the fishery would potentially exclude 74 eligible vessels from fishing for queen scallops in the Isle of Man's territorial waters. However, only 69 of these vessels are predicted to fish for queen scallops, based on historical fishing activity. At present there are no multi-rig trawlers fishing for queen scallops within the 12 nm limit and as such no such vessels would be impacted as a result of a ban on this type of fishing. Due to the limited availability of data and research the impacts of a proposed limit on queen scallop net spread to a maximum of 12 fathoms (c. 24 m) is unclear.

In November 2009 Ramsey Bay was closed to dredging for scallops as stocks were seen to have becom... more In November 2009 Ramsey Bay was closed to dredging for scallops as stocks were seen to have become depleted. Later the Ramsey Bay Marine Nature Reserve (RBMNR) was created, part of which (45.9 km 2 ) was designated a fisheries management zone (FMZ). In 2013 a lease to manage the FMZ was granted to the Manx Fish Producers Organisation (MFPO).

awaited. Current zones proposed by DAFF to be closed to queen scallop dredging would be effective... more awaited. Current zones proposed by DAFF to be closed to queen scallop dredging would be effective in reducing the risk of impact of queen scallop dredging on most areas of horse mussel reef and maerl beds identified. However, the current proposed zones may leave the Sabellaria spinulosa vulnerable to queen scallop dredge damage. Statutory protection of some of these habitats is recommended and could enhance the role of habitats such as maerl as a nursery area for queen scallops.

ABSTRACT Obtaining accurate data on abundance is vital to undertaking viable stock assessments of... more ABSTRACT Obtaining accurate data on abundance is vital to undertaking viable stock assessments of commercially exploited species. Satellite Vessel Monitoring Systems (VMSs) combined with fisheries logbooks have the potential to provide an abundant source of data with greater spatial and temporal coverage than research surveys. However, to date it has not been demonstrated how well VMS-derived abundance or biomass indices reflect research survey results. In this study we compared biomass indices of scallops derived from (i) fishing vessel surveys, (ii) research vessel surveys, and (iii) fishery-dependent data using VMSs and logbooks. In most cases there were strong relationships between biomass indices of Pecten maximus from fishing vessels and the research vessel. There were stronger relationships between P. maximus biomass indices from fishery-dependent VMS and logbook data and research vessel data at the beginning of the fishing season, when abundance was higher, but weaker relationships at the end of the fishing season. The time and location of sampling affected biomass estimates over short periods, and without standardizing to location and vessel, biomass depletion was masked. Fishery-dependent data provides a valid means of assessing relative scallop abundance and may prove equally viable in other fisheries with appropriate standardization of Catch Per Unit Effort (CPUE) data, making real-time management of fisheries increasingly feasible.

Journal of Shellfish Research, 2007

Methods in Ecology and Evolution, 2013

ABSTRACT Monitoring and assessment of the status and distribution of marine seabed habitats is ne... more ABSTRACT Monitoring and assessment of the status and distribution of marine seabed habitats is needed to support existing and emerging environmental policy commitments. Traditional monitoring of habitats and associated species using grabs and trawls is costly and labour intensive and might usefully be complemented by cheaper and more readily automated methods that can be used at higher frequencies and/or on larger spatial scales. We develop and apply two methods to measure seabed habitat complexity and demonstrate how they can be used to describe impacts (e.g. fishing gear impacts) and monitor recovery. The first method relies on the analysis of deviations in a laser line projected on the seabed. The second method is based on the pixel value distribution in seabed photographs. We use both methods to quantify the complexity created by different substrates and habitat-forming species and to establish links between habitat complexity and faunal diversity (richness) and abundance. The habitat complexity index calculated with the laser line method provided a reliable index of complexity across a range of habitat types, showing a monotonic increase with coarseness of the substratum and the abundance of sessile epifauna. Pixel value distributions in the photographs did not reflect the increase in complexity due to sessile epifauna but only reflected substratum differences. Results suggested that the laser line method would be suitable for monitoring the effect of disturbance on habitats ranging from gravelly sands to rock, and their subsequent recovery. The photographic method would be better suited to assessing complexity and heterogeneity of the substratum. Both methods complement conventional biological sampling and can be used at higher frequencies and/or on larger spatial scales per unit cost. The laser line method has considerable potential to support demands for frequent monitoring of seabed habitats and human impacts at a range of spatial scales. It is less costly and labour intensive than existing approaches and can be deployed from vessels of many sizes.

Marine Environmental Research, 2012

The negative impact of demersal fishing gears on the marine environment may be mitigated by utili... more The negative impact of demersal fishing gears on the marine environment may be mitigated by utilizing less damaging fishing gears. Within this context three queen scallop fishing gears were tested for their catch efficiencies and their environmental impact on benthos: a traditional 'Newhaven' dredge, a new dredge design with a rubber lip instead of the traditional teeth as its main new design feature and an otter trawl. Both, the new dredge and the otter trawl showed high catches and relatively low by-catches. Catches made with the traditional dredge were lower and contained larger amounts of nonetarget species. Both dredges primarily caught invertebrate species, while by-catches of the otter trawl were dominated by demersal fish. The impact of these gears on the benthic biota demonstrated that while no effects were detected for the otter trawl both dredges showed similar negative effects. Clear negative effects were evident for the brittlestar Ophiura ophiura while positive trends for the common starfish Asterias rubens and the hermit crab Pagurus bernhardus indicated scavenging effects. Due to its higher catch efficiency the new dredge caused less damage per unit catch compared to the traditional dredge, yet compared to the otter trawl it appears less environmentally friendly. However, the new dredge may be an alternative to the otter trawls for fisheries where the by-catch of demersal fish has been identified as a significant problem.

Marine Ecology Progress Series, 2011

To implement effective fisheries management, it is important to understand the variables influenc... more To implement effective fisheries management, it is important to understand the variables influencing the distribution and intensity of fishing effort. The functional response of consumers to the availability of prey determines their impact on prey populations. The relationship between predator and prey observed in nature also applies to fishers and the populations they target. The present study focuses on the behaviour of a scallop dredging fleet fishing for Pecten maximus around the Isle of Man during a single fishing season. The functional response was investigated by examining the relationships between catches and fishing effort, scallop abundance and other variables. Scallop abundance was depleted rapidly during the first month of fishing. The increased patchiness of scallops towards the end of the season probably reduced their catchability, but fishers were able to maintain catch rates at intermediate abundance levels. The functional response did not conform to a particular type, but there was latent fishing capacity in the fishing fleet even at the highest levels of abundance. Therefore, reducing the number of vessels would not necessarily reduce fishing mortality unless combined with a reduction in the fishing power of individual vessels.

Marine Ecology Progress Series, 2010

ABSTRACT Stock assessments of crabs commonly rely on catch per unit effort (CPUE) data derived fr... more ABSTRACT Stock assessments of crabs commonly rely on catch per unit effort (CPUE) data derived from catches in baited traps. Baited traps have been used for many years to estimate the relative abundance of predators in the marine environment. However, traps may result in biased estimates due to inter- and intra-species variations in physiology and behaviour. The aim of this study was to determine the suitability of CPUE as a proxy for the relative abundance of Carcinus amends. Crab abundance estimates were obtained using underwater camera surveys. The study was conducted on commercial mussel beds in the Menai Strait, United Kingdom. CPUE data were obtained from the local C. maenas fishery operating over the mussel beds. The influence of temperature-dependent feeding rates on CPUE was predicted from the number of mussels consumed at different experimental temperatures in laboratory aquaria. Both CPUE and estimated abundance showed marked seasonal variation. Abundance maxima preceded temperature maxima by 2 mo. CPUE increased with temperature up to 15 C, while relative crab abundance based on visual surveys exhibited a strong positive correlation with day-length. CPUE appears not to be a suitable proxy for the relative abundance of C. maenas because of the effects of temperature on crab activity levels and thus catches.

ICES Journal of Marine Science, 2012

... VMS position, time, speed, and anonymous vessel identification data for king scallop dredgers... more ... VMS position, time, speed, and anonymous vessel identification data for king scallop dredgers (DR) and queen scallop otter trawlers (OT) in the territorial waters of the Isle of Man for the period between November 2008 and October 2010 were provided by the Isle of Man ...

Fish and Fisheries, 2013