It is common to uncover a fishing effect and call it an indicator. At the last count there were several thousand proposed fisheries indicators – however there are incredibly few indicators available to managers. It took 5 or more years for our ICES working groups to define what a large fish is!
Indicators of the effects of climate change on migratory species
The government agencies implementing the Convention of Migratory Species (www.cms.int) would like to know how climate change might be affecting their species. So we tried to scope out the kinds of indicators that might guide these policymakers. One illuminating outcome was that there are many indicators of change that could not summarize the net effect of climate change on the viability of the species. Three issues arose (1) climate impacts on components of an animal’s life cycle – such as their fledging success (2) climate impacts on the geographical distribution of species and (3) the increasing match-mismatch between the timing of primary and secondary production and the timing of emergence and peaks in abundance of predator species. These are all important issues, however we do not know yet what the impact of these issues are on the population growth rate of species. This is a key challenge for the future.
Indicators in support of the Convention on Biological Diversity
The only marine indicator used to monitor progress toward the 2010 target of hating and reversing the rate of biodiversity loss is the Marine Trophic Level index. While this has been a fantastic vehicle for making people aware of the ecosystem effect of fishing. It is NOT and indicator of biodiversity, and it is especially not and indicator of the state of biodiversity in our oceans. It is an indicator of trophic level of the fish we remove FROM the sea. Does it tell us anything about what is left in the sea? NAother problem with the MTI it that it may tell you whether the mean trophic level of the catch is increasing or decreasing – it doesn’t tell you how to manage fish stock and fishing in order to change the index. There are fundamental challenges to making this an operational indicator at nation scales.
Threat status of large predatory fishes
People really care about the bigger more charismatic species an alternative approach that captures both function and biodiversity is an indicator of the year-by-year change in the threat status of large fishes. We have calculated the threat status of the 26 largest species (left) in the North Sea and added them together to produce the Large Predatory Fish Index.
The index is the weighted average threat status of twenty three large predatory fishes in the North Sea from 1982 to 2001 estimated using World Conservation Union (IUCN) Red List decline criteria. The index was calculated from the weighted average of the threat scores of individual species in each year and varies from 0 to 3. A score of 0 indicates that on average all species are safe, 1 = on average all species are Vulnerable, 2 = on average all species are Endangered, 3 = on average all species are Critically Endangered. For example a score of 1 means that on average all species are vulnerble. However some may be safe and some may be Endangered or Critically Endangered. Threat status is measured over the ten years prior to the reporting date and hence reporting spans only from 1992-2002.
So what does it mean?
A suitable reference trajectory, consistent with the World Summit on Sustainable Development commitment to “achieve by 2010 a significant reduction of the current rate of biodiversity loss” would be a significant reduction in the rate of increase in this indicator before 2010.
A target reference point should be to achieve an index score of 0 (no threatened species).
A limit reference point could be to keep the score under 1 (avoid all species vulnerable).
Current Status The Large Predatory Fish Index has declined since the mid-1990s to a point beyond the limit reference point (score of 1). So on average all species are Vulnerable.