Exploring the scales and drivers of blue transitions of marine wild-capture fisheries to mariculture in California, U.S.A

Commercial capture fisheries worldwide are susceptible to perturbations and sudden declines, also known as shocks. While management reforms and diversification within wild fisheries have provided some stability, it is less clear how parallel sources of seafood production, such as aquaculture, fit into these dynamics, past and present. Marine aquaculture (mariculture) is one way to increase seafood supply as demand increases and fisheries landings potentially become more variable. This study examined historical trends in marine fisheries and mariculture in the state of California, U.S.A., with an aim to empirically understand local ‘ blue transitions ’, i.e. shifts from wild to farmed production. Using shock, breakpoint and random forest time-series analyses, we explored the potential influence of fisheries variability and changes to aquaculture policy on temporal trends in mariculture production over time. We found supportive evidence that blue transition dynamics have occurred in California. Specifically, we identified a correlation between large fisheries shocks in both volume and value and subsequent regional growth of mariculture. Further, the coefficient of variation (CV) for wild catch volume was a positive predictor—along with California population and U.S. GDP—in explaining mariculture growth from 1972 to 2018 ( R 2 ± SD = 0.92 ± 0.03). Numeric measures of state and federal policies (e.g. number of regulations) did not improve model predictions, but we found a proliferation of restrictive state regulations (2:1 restrictive to enabling) that may have stymied growth since the 1980s. Because data limitations and misclassification challenged our ability to fully assess wild-farmed dynamics, we also conducted a longer historical, semi-quantitative analysis of California oyster fishing and farming (1888–2018), which highlighted a full blue transition that informs more recent trends. This study underscores the importance of local and state-level fisheries and policy dynamics in shaping mariculture’s role in seafood production.