Fisheries feel costs of ignoring planet's health.
Brown, C, E Fulton, H Possingham and A Richardson. 2011. How long can fisheries management delay action in response ot ecosystem and climate change? Ecological Applications http://dx.doi.org/10.1890/11-0419.1.
Keeping the status quo and delaying management decisions as ocean fish populations flux with climate can lead to unsustainable fisheries as well as lost opportunities to harvest the fish that are flourishing, according to the authors of a study published in the journal Ecological Applications.
They found that a faster turnaround – in less than five years – to implement scientific recommendations to restrict or increase catch sizes would ease population collapses and be a step towards maintaining fisheries into the future. The study illustrates the benefits of a flexible management system that can rapidly respond to increases and decreases in fish populations brought on by climate change or other types of environmental changes. These benefits include sustaining fisheries as an important food source and as a major industry.
The effects of changes in climate – such as water temperature and ocean chemistry – and in the environment – including shifts in nutrients, food or ocean currents – can have drastic effects on fish populations. In some cases, these changes can lead to declines in fish populations and possible collapse of a fishery, as with Australia's orange roughy fishery. In other cases, the changes can increase populations to benefit a fishery. Complicating matters is that wild fish populations also naturally vary year to year.
Each of these has major implications for how specific fisheries are managed in the midst of change.
Fisheries management is complex. First, it is difficult to accurately measure the size of current fish populations and to predict future changes. Second, social and political issues involving jobs and food supply that are necessary to maintain a viable, profitable seafood industry hinder management. These issues can delay changes in management practices, making it difficult to respond to changes in fish stocks.
In this study, researchers looked at how the timing of management responses to changing fish populations can impact fisheries and catch size. The scientists gathered data from published studies and reports to simulate different scenarios. They included 1) different growth rates of a harvested fish population, 2) recommendations of catch limits based on scientific monitoring results and 3) delays in management decisions (The time it takes to increase or reduce harvest levels after a recommendation is made, ranging from 0 to 50 years.). They predicted how delays under different scenarios would impact the harvest (summed over 50 years) and viability (probability of collapse over 50 years) of a fishery responding to changes in the environment.
They found that in general, management delays greater than five years increase the probability that a fishery will collapse, particularly for populations that are declining. Delays result in lower, more variable harvests over the long term. Populations that are increasing can offset the costs of delays, especially when delays are short. However, populations with fast and highly variable growth rates are particularly at risk of collapse from delays.
The authors also found that adjusting the maximum harvest limit was both an effective way to compensate for long-term management delays and the most effective way to adjust management.
The study forewarns of the importance of nimbly adapting management practices in response to climate and environmental change in order to sustain fisheries. However, the authors point out that the stronger governing and enforcement needed to quickly adapt to harvest levels may be difficult to attain and will require collaboration among fishermen, managers and scientists.
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