4. Discussion and conclusion
When evaluating the effectiveness of mitigation measures on a biological reserve or any other delineated geographic space, the choice of summary metrics may greatly influence the perceived conservation value. In particular, if the activities being mitigated are heterogeneously distributed across the reserve, two choices for summarization are possible: by activity or by area. We evaluated mitigation on its overall effect to Stellwagen Sanctuary, a well defined geographic area. Thus, we thought it most informative if zones within the sanctuary not influenced by speed restrictions (low traffic volume above 10 knots) be given equal weight to areas greatly influenced so as to provide a geographic perspective to the evaluation process. Although completing an event-based analysis (e.g. counting the number of percent events where speed was reduced) might portray higher levels of threat reduction, those gains may be highly overstated for the reserve as a whole.