Conclusions

Any assessment process or procedure, from EIA, Strategic Environmental Assessment (SEA), Risk Assessment (RA) or Vulnerability and/or Sensitivity Assessment, is an exercise in information collation, management and evaluation designed to enable or support decision making. All assessment procedures aim to use the best available scientific evidence but inherent in the procedure is the fact that we do not possess a complete understanding of the system we are trying to assess.

Therefore, sensitivity assessment in the marine environment has often been seen a ‘holy grail’, designed to synthesise all available information, in a transparent and systematic manner in order to allow users to decide on conservation or management priorities.

Numerous procedures have been developed over the past decades to address sensitivity of marine habitats. Yet all have been limited by the evidence base (on marine impacts, fishing intensity and community response), and design constraints so that they are not universally applicable.

As a result, no one method has gained favour with the marine environmental management community as a whole, and even less within the marine science community. The marine environmental management community has long sought a methodology that can be applied to all situations, at all scales, and while the

assessment procedures, as shown in Section 6, are all designed to answer questions at prescribed scales and for specified activities. The scientific community, however, has tended to avoid ‘expert judgement’ and ‘ranking’ exercises in favour of more empirical assessment procedures that give less scope for bias.

The principle aim of this review was to examine the feasibility of a procedure to

address the vulnerability of habitats to commercial fishing activities as part of the WFD commercial risk assessment. While there is an evidence base for fishing impacts on habitats (reviewed in Section 3 as resistance and recovery of biogenic features and geomorphological sedimentary features), in general much more interest has been focussed on impacts on the biological components of habitats. In order to be comprehensive we have therefore considered both species and community level sensitivity parameters and sensitivity assessments based on species and the biological assemblage. Species create much of the physical habitat structure on the seabed, e.g. pits, burrows, biogenic reefs, and are impacted by fishing impacts on habitat

complexity. Therefore, biological sensitivity is an important component of any assessment of sensitivity to morphological impacts. However, any examination of morphological impact needs to address sensitivity to physical habitat modification (e.g. substratum change or modification) and the physical aspects of its natural restoration (e.g. sediment supply, water flow).

The above review leads to the following general conclusions.

i. Clear definitions of terms are vital for any assessment procedure, and terms such as resistance, intolerance, resilience recoverability, sensitivity and vulnerability need to be carefully defined and explained.

ii. Habitat groups (derived from the UK marine habitat classification) provide discernable units for assessment that are relatively easy to explain to stakeholders from multiple marine sectors, including the public.

iii. Biogenic habitat and those habitats dominated by long-lived, slow growing species are amongst the most sensitive to damage by fishing activities.

Due to their prolonged recovery period, maerl beds may be best viewed as non-renewable resources, lost forever if removed or destroyed.

iv. Soft sediment habitats vary in sensitivity depending on the mobility or cohesiveness of the sediment as well as the nature of the communities they support. The rate at which the physical habitat ‘recovers’ from damage is an important component of the rate at which the habitat as a whole is able to recover.

v. The impacts of fishing activities of chalk reef habitats are the least well studied of all the habitats examined.

vi. A large number of parameters (130) have been used in the 70 past studies examined to assess the sensitivity of habitats. These range from physical, chemical and biological parameters and include estimators of community structure and function.

vii. Nevertheless, no single descriptor or parameter can effectively or reliably explain the impact of fishing on community structure and habitat response. A number of parameters are required to describe the nature of the activity, the nature of the impact or response, the potential rate of recovery and overall sensitivity.

viii. The most used parameters include a suite of biological traits that describe a species or habitat (especially morphology and environmental position), their life history, the physical nature of the habitat itself (especially for soft

sediments), and their contribution to ecosystem function (e.g. biogenic habitats) and function (e.g. biomass and productivity).

ix. However, biological traits alone cannot necessarily capture all aspects of the sensitivity of marine habitats, due to lack of data and understanding, and there is an important role for expert judgement in the assessment procedure.

x. Recent meta-studies and empirical studies on the effects of fishing on marine habitats (primarily soft sediments) has significantly improved our understanding of the relationship between fishing intensity, gear type, substratum type and impact and recovery.

xi. Studies of the effects of different fishing intensities are underpinned by VMS data on the movement of fishing vessels.

xii. The setting of clear, well defined, thresholds is a vital part of the

assessment procedure. Thresholds include definitions of fishing intensities and gear types but also include thresholds of damage (acceptable vs. unacceptable), scales of resistance, resilience, sensitivity and vulnerability. xiii. The sensitivity assessment methodologies reviewed were all developed for

specific purposes, to answer specific management questions. Therefore, they are not completely applicable outside their original design parameters. xiv. Sensitivity assessment is designed to manage uncertainties and

information gaps. Although our understanding of the effects of fishing has grown considerably over the last twenty years, information gaps remain. xv. Nevertheless, the existing sensitivity assessment methodologies provide a

wide range of tools that could be applied to vulnerability assessment. Therefore, the development of an approach to the assessment of the vulnerability of habitats to commercial fishing activities is feasible.