A Complex Past: Historical and Contemporary Fisheries Demonstrate Nonlinear Dynamics and a Loss of Determinism
Klein, E., Glaser, S., Jordaan, A., Kaufman, L., & Rosenberg, A. (2016). A complex past: historical and contemporary fisheries demonstrate nonlinear dynamics and a loss of determinism. Marine Ecology Progress Series, 557, 237-246. doi:10.3354/meps11886
Summary
- Bottom line: Using data from Canada’s Bay of Fundy dating back to 1873, this study indicates that fish catch dynamics are nonlinear before and after the advent of industrial fishing, but less predictable following industrial fishing. This suggests intense fishing pressure may make predicting the trajectory of fish populations challenging.
- Background:
- Scientists sometimes assume complex systems like fisheries can be studied by breaking them into their constituent parts and then re-assembling them to predict the overall behavior of the system. This approach does not work, however,if parts of the system are nonlinear, which means that their dynamics depend on other factors in the system.
- While nonlinear systems can be complex and sometimes chaotic, they can still be predictable using appropriate methods.
- Predictability of nonlinear signals can be a warning sign of system vulnerability.
- Methods: This study used Canadian government catch data from nine species and 11 counties around the Bay of Fundy before and after industrial fishing. The researchers used a technique called empirical dynamic modeling (EDM) to identify non-linear dynamics.
- Findings: The study found that catch data were less predictable following industrial fishing. This reduced predictability can have important implications for fisheries management, and may indicate that fishing can disrupt marine populations beyond decreasing stock abundance. According to these results, fishing has the potential to change the fundamental dynamics of the system. It will be critical to find ways to account for this in stock assessments, beyond a single mortality rate, especially in light of climate change.
The full publication is available here: http://www.int-res.com/abstracts/meps/v557/p237-246/.
