"We now have the technology to overfish almost every imaginable marine resource. The question is, do we have the political will and the social and cultural institutions to restrain ourselves?" Ray Hilborn, from the book Overfishing: What everyone needs to know (2014) "Resource managers attempt to manage people not fish" Jentoft (1997) Recent fisheries effort has been devoted to the development of increasingly complex models that account for uncertainty about resource dynamics (i.e. environmental stochasticity) and where harvest is coupled dynamically with resource abundance. However, much less attention has been devote to uncertainty and risks arising from human responses! In some recent contributions, by using rich time series from Lake Erie Walleye and Yellow perch, we investigated if weak or delayed adjustments of quota to changing resource abundance may contribute to long-term cycles in population abundance and risk of stock collapse. We also compared the dynamics of commercial and recreational fishermen.
Lagged quota adjustment in Lake Erie walleye fishery
Weak compensatory response in quota modification by resource managers has been hypothesized to introduce lags between changes in abundance and harvest that can result in quasi-cyclic variation in population abundance, which can increase the risk of fishery collapse. Data gathered during 1975-2000 from the Lake Erie walleye commercial fishery indicate slow compensatory response in quotas to changes in stock abundance, entraining effort and harvest. Following a period of low walleye abundance in the late 1990s, a change in management policy led to much faster quota response to perceived changes in abundance. Following this change in policy, there was no significant evidence of lags among stock abundance, quotas, and harvests, nor was there evidence of periodic oscillation in these variables. These results suggest that weak incremental changes in quota adjustment by fishery managers can contribute to pronounced lags between stock abundance and harvest levels that may not be beneficial in meeting long-term economic and biological objectives for sustainable management (Turgeon et al. in review; Ecological Applications).
Fish to live or live to fish! Different dynamics in commercial and recreational fishermen
Very few studies have compared the effects of recreational and commercial fisheries on resource abundance, and none compared how their dynamics (i.e. changes in effort and harvest) respond to changes in resource abundance. By using time series from the walleye and yellow perch fisheries of Lake Erie, we compared the dynamical response of recreational and commercial fisheries to changes in resource abundance over more than 35 years. The dynamics of commercial fisheries are much less responsive to changes in resource abundance than are those of the recreational fisheries in both species but this pattern is much more pronounced in walleye. The dynamics of the commercial fisheries dynamics lagged behind change in resource abundance in walleye and in yellow perch whereas the recreational fisheries were in almost perfect synchrony with changes in resource abundance. Delayed management response to change quotas directly determines commercial fisheries dynamics and changes in both species but resource and fishing quality determines the dynamics of recreational fisheries. A faster compensatory response of recreational fishermen may help buffer fluctuations in resource abundance created by a management induced delay response of commercial fishermen. Furthermore, our results confirm that commercial effort and harvest data may not be reliable indicators of stock status and, contrary to previous work on recreational fishery catch rates, data from recreational fisheries should be more fully considered in stock assessments because of their strong correlation with changes in resource abundance (Turgeon et al. in review.).