Increasing the harvest for mussels Mytilus edulis (L.) without harming oystercatchers Haematopus ostralegus (L.)

Oystercatchers Haematopus ostralegus (L.) arriving on their wintering grounds at the end of summer require there to be 6-8 times more mussel Mytilus edulis (L.) biomass available on their feeding grounds than they will consume over the winter if the birds’ normal high survival rate until spring is to be maintained: that is, their ‘Ecological Requirement (ER)’ is considerably larger than their ‘Physiological Requirement (PR)’. The ratio ER/PR was termed the ‘Ecological Multiplier (EM) and has been applied to a number of shellfisheries to calculate the Total Allowable Catch (TAC). The high value of the EM, however, has meant that mussel fisheries have suffered from much reduced harvests and thus economic difficulties. This paper proposes two methods by which the TAC could be increased without any predicted impact on the birds. In the ‘roll-over’ approach, the surplus biomass remaining at the end of one month is harvested during the next. In the ‘delayed start’ approach, the EM is not set at the beginning of autumn but at the beginning of the winter, which is when birds begin to starve. The two approaches can be applied together and would enable many more mussels to be harvested than is currently allowed without reducing oystercatcher survival. In the test case presented here, the TAC over the winter could be increased from 5% to between 35% and 45% of the standing crop of mussels present in September when the birds arrive

A framework for climate change adaptation indicators for the natural environment

Impacts of climate change on natural and human systems will become increasingly severe as the magnitude of climate change increases. Climate change adaptation interventions to address current and projected impacts are thus paramount. Yet, evidence on their effectiveness remains limited, highlighting the need for appropriate ecological indicators to measure progress of climate change adaptation for the natural environment. We outline conceptual, analytical, and practical challenges in developing such indicators, before proposing a framework with three process-based and two results-based indicator types to track progress in adapting to climate change. We emphasize the importance of dynamic assessment and modification over time, as new adaptation targets are set and/or as intervention actions are monitored and evaluated. Our framework and proposed indicators are flexible and widely applicable across species, habitats, and monitoring programmes, and could be accommodated within existing national or international frameworks to enable the evaluation of both large-scale policy instruments and local management interventions. We conclude by suggesting further work required to develop these indicators fully, and hope this will stimulate the use of ecological indicators to evaluate the effectiveness of policy interventions for the adaptation of the natural environment across the globe