Science Advisory Report 2018/043

Framework to support decisions on authorizing scientific surveys with bottom-contacting gears in protected areas with defined benthic conservation objectives

Summary

• A number of protected area and existing and proposed sensitive benthic area closure (herein protected area) boundaries overlap the geographic areas of scientific surveys using bottom-contacting sampling gears.
• In many DFO regions, scientific surveys using bottom-contacting gears have been conducted for several decades and are important for resource status assessment, recovery potential assessment, monitoring of species of conservation concern, and ecosystem status reporting.
• Immediate effects of most mobile bottom-contacting gear on benthic features include the loss of erect and sessile epifauna, habitat modification including scouring of glass sponge reefs, and removal of structure-forming taxa such as corals and sponges. Mortality mostly occurs through direct contact/removals and secondarily by predation. Sediment plumes from trawls can also cause smothering in filter-feeding organisms which can lead to mortality.
• The extent of physical impact of bottom-contacting gears on seabed habitat and fauna is related to the penetration of the gear in the sediment, collision impacts, removals by the gear, and sediment mobilization. The area impacted is a function of the area covered by a single sampling event (swept area) and the area affected by sediment resuspension from a sample, summed over the distribution of all samples.
• A proposed proxy of the level of harm to benthic habitat caused by scientific surveys with bottom-contacting gears is the relative magnitude of the recurrence time interval of the activity compared to the expected recovery time of the benthic components.
• The recurrence time interval (in years) for an activity, defined as the average time between successive benthic sampling impacts at a given site, is the inverse of the annual proportion of the protected area impacted by the activity when the distribution of sampling sites in the area is random.
• Recovery time in this report is defined as the length of time it takes for the benthic attribute to return to its state prior to scientific survey impact. The potential for recovery of benthic fauna following disturbance by bottom-contacting gear is determined by the characteristics of the benthic components. Longevity of individuals or the long periods over which some benthic habitat features develop must be taken into consideration.
• Taxa with lifespans or benthic features with ages that are less than one-tenth the estimated recurrence times of a benthic interacting science activity are likely to have time to recover to the levels that existed prior to the impact of the sampling activity. Taxa with lifespans or benthic features with ages that are greater than about a tenth of the recurrence times (an order of magnitude scale) may be susceptible to long-term degradation and lack of recovery.
• The choice of needing recurrence time to be ten times larger than lifespan to avoid long-term degradation (or lack of recovery) is important given uncertainties and knowledge gaps of benthic invertebrate life histories, indirect effects of gear impacts not quantified in the swept area estimates, and knowledge gaps of benthic community recovery rate and factors.  It is meant to help prevent overestimation of recovery potential.
• In lieu of excluding scientific activities from protected areas, a switch to alternative monitoring methods or modifications to existing survey gear or procedures should be considered to mitigate impacts of the scientific activities on benthic features.
• The importance of scientific samples collected within a protected area with respect to the integrity of the survey’s historical time series is case specific. A key consideration is the introduction of a time-varying bias in the time series of survey-based indices resulting from the exclusion of samples from protected areas. Such a bias will occur if the spatial distribution of a stock changes with respect to the protected areas.
• A national framework was developed that describes the information gathering process that will assist the management sectors in any region of Canada in their review for authorizing proposed scientific activities with bottom-contacting gears in protected areas. The framework is intended to facilitate dialogue between the science survey proponent(s) and the decision-making sector.
• Operationally, reviews of scientific activities must not be done in isolation. In some cases, protected areas may overlap more than one DFO administrative region. Coordination of requests, in some cases at the bioregional scale at which many surveys occur, will be required to ensure that the cumulative footprint of all proposed scientific activities on an annual basis is properly considered. Similarly, the potential consequences on scientific advice of excluding survey activities from all protected areas that overlap with a survey should be considered. The timelines for notification, review, and authorization decisions may therefore be much longer than indicated in policies or regulations.
• Some of the review associated with authorizations of scientific surveys in protected areas can be done periodically (effects of excluding stations from protected areas, recurrence intervals) whereas other components will require annual inputs (exact locations of sets within a protected area).

This Science Advisory Report is from the January 16 to 18, 2018 national peer review on the framework to support decisions on authorizing scientific surveys with bottom contact gears in protected areas with defined benthic conservation objectives. Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Schedule as they become available.

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