https://hull-repository.worktribe.com/preview/464258/MPB-D-10-005861.pdf

Management of the marine environment: integrating ecosystem services and societal benefits with the DPSIR framework in a systems approach.

Assessment of ecosystem function following marine aggregate dredging

Morphological characteristics of the Basque continental shelf (Bay of Biscay, northern Spain); their implications for Integrated Coastal Zone Management

Morphological characteristics of the Basque continental shelf (Bay of Biscay, northern Spain); their implications for Integrated Coastal Zone Management. Geomorphology 118(3-4):314-329

Summary
The Ecosystem Approach to Fisheries requires that managers take account of the environmental impacts of fishing. Towed bottom-fishing gears disturb seabed habitats and cause mortality of benthic invertebrates. Measurements of recovery rates of marine habitats after fishing disturbance can provide insight into spatial variations in resilience and may be used to assess the sustainability of these fishing impacts and inform the development of appropriate management strategies.
To measure recovery on real fishing grounds at fishery- and management-relevant scales, we estimated the post-disturbance recovery rates of epifaunal marine benthic communities on coarse and hard substrata across >4000 km² of seabed where the patchy distribution of bottom fishing in space and time creates a mosaic of habitat patches at different stages of recovery.
The history of fishing events at each location was described using satellite vessel monitoring system (VMS) data. Recovery rates were extrapolated from the relationship between time since the last fishing event and abundance of epifaunal benthic invertebrates with life-history traits that are expected to make them sensitive to fishing.
Recovery of abundance of all species and functional groups (medium to medium-large size, medium to long life span, suspension feeding, high body flexibility and low mobility species) was estimated to take 10 years, depending on the group, with faster recovery in areas with faster tidal currents.
The recovery of large species was faster when conspecifics were abundant within a radius of 6 km, suggesting an important role for maintaining local sources of recruits to repopulate impacted areas.
Synthesis and applications. We used a new method to estimate the recovery rate of benthic communities and to describe spatial differences in sensitivity to fishing. Bottom fishing in areas that recover quickly will minimize overall impacts, while leaving unfished patches of seabed will enhance recovery rates in fished areas. We conclude that management plans which limit bottom trawls and dredge fisheries to more resilient areas and maintain unfished patches within these areas will minimize the collective impacts of a given amount of fishing effort on seabed habitats.

https://besjournals.onlinelibrary.wiley.com/doi/pdf/10.1111/1365-2664.12277

Quantifying recovery rates and resilience of seabed habitats impacted by bottom fishing

The aim of this study was to investigate the effect of dredging intensity on the physical and biological recovery times of the seabed following marine aggregate dredging. Two areas of seabed, previously subject to, respectively, relatively high and lower levels of dredging intensity, were identified on the Hastings Shingle Bank. Two reference areas were also selected for comparative purposes. All four sites were monitored annually over the period 2001–2004, using a combination of acoustic, video and grab sampling techniques. Since the site was last dredged in 1996, this was intended to provide a sequence of data 5–8 years after cessation of dredging. However, an unexpected resumption of dredging within the high intensity site, during 2002 and 2003, allowed an additional assessment of the immediate effects and aftermath of renewed dredging at the seabed. The early stages of recovery could then be assessed after dredging ceased in 2003. Results from both dredged sites provide a useful insight into the early and latter stages of physical and biological recovery. A comparison of recent and historic dredge track features provided evidence of track erosion. However, tracks were still visible 8 years after the cessation of dredging. Within the high dredging intensity site, recolonisation was relatively rapid after the cessation of dredging in 2003. Rather than indicating a full recovery, we suggest that this initial ‘colonization community’ may enter a transition phase before eventually reaching equilibrium. This hypothesis is supported by results from the low intensity site, where biological recovery was judged to have taken 7 years. Further monitoring is needed in order to test this. An alternative explanation is that the rapid recovery may be explained by the settlement of large numbers of Sabellaria spinulosa. As the resumption of dredging within the high intensity site limited our assessment of longer-term recovery it is not yet possible to assume that a 7-year biological recovery period will be applicable to other, more intensively dredged areas at this or more distant locations.

Recovery of the seabed following marine aggregate dredging on the Hastings Shingle Bank off the southeast coast of England

Performance of selected indicators in evaluating the consequences of dredged material relocation and marine aggregate extraction

This paper develops models of the initial impact of marine aggregate extraction on a benthic assemblage. We predict the effect of dredging on species numbers and abundance assuming spatial randomness of individuals. We extend the model to allow for spatial clustering of individuals using a Matern process. Data from a controlled field experiment are used to develop a framework for estimating species reduction. This involves modelling the spatial pattern of individuals before dredging using a Matern process, the impact of dredging at an individual level, and the probability that a species is not seen in a post-dredging survey. The framework was used to estimate that, of the 41 species that were seen in a pre-dredging survey but not in a post-dredging survey, between 0 and 14 were eliminated (with 95% likelihood) rather than escaped detection. The most likely number eliminated was 4.

Sian E. Boyd

Papers

Recovery of the seabed following marine aggregate dredging on the Hastings Shingle Bank off the southeast coast of England

Performance of selected indicators in evaluating the consequences of dredged material relocation and marine aggregate extraction

Modelling the effects of marine aggregate extraction on benthic assemblages

Benthic Communities, Ecosystems and Fisheries