Since 2013, CCIRA has been using science and traditional knowledge to build the most extensive database for rockfish ever compiled for the Central Coast. This growing body of work is providing insights that can help improve the design of the Marine Protected Areas network in our territories and beyond.
1. Bigger is better
Big old rockfish are reproductive powerhouses, birthing more larvae (live young) than younger, smaller females. The difference can be dramatic, ranging in some species from a mere 100 thousand young when mothers first become reproductive to upwards of two-and-half million young when mothers become older and reach larger sizes. In other words, big old fish play outsized roles for maintaining sustainable rockfish fisheries.
Unfortunately, these same fish are targeted by fishers. When populations are overfished, they lose their big old fish, threatening the sustainability of local fisheries and the ability of a population to recover from over-exploitation.
2. Central Coast Rockfish are struggling
Rockfishes in British Columbia were severely depleted from the late 1970s to the late 1990s as commercial and recreational fisheries expanded. As an example, CCIRA research shows that the average size of yelloweye rockfish caught by Indigenous fishers on the Central Coast has declined by 45% since the 1980s. And, despite more conservative fishery management since the 2000’s, the average body sizes of yelloweye and quillback rockfish have continued to decline rapidly in the Central Coast. On average, yelloweye rockfish also have become younger every year, as the older fish become scarcer in the population.
3. Rockfish Conservation Areas can help recovery
There are 36 species of rockfish in BC waters with myriad differences between them. For example, our research shows that some species prefer deep water with big rocky structure, while others prefer more moderate depths with less rocky structure. Some rockfish species also grow more quickly than others. Yet, despite these differences between species, recent dive surveys by CCIRA found that a wide range of rockfish species had larger body sizes inside two Rockfish Conservation Areas (RCAs)—places where most commercial and recreational fisheries are prohibited—than in adjacent unprotected areas. These results are encouraging. They are also consistent with research in California where there is ample evidence that protected areas have helped the recovery of many rockfish species.
“Recent dive surveys by CCIRA found that a wide range of rockfish species had larger body sizes inside two Rockfish Conservation Areas than in adjacent unprotected areas.”
Yet the same CCIRA research also found that at four other RCAs rockfish body sizes did not differ between protected and fished areas. In other words, 4 of 6 RCAs examined appeared to not be meeting their conservation objectives, and it is important to examine why. “We need to investigate whether the lack of increase in body sizes at 4 RCAs reflects non-compliance by recreational fishers, poorer habitat, too small a size of the protected area, impacts of commercial fisheries permitted in RCAs (such as mid-water trawls), or a combination of these factors,” says CCIRA Science Coordinator Alejandro Frid. “DFO has invested almost no resources in compliance monitoring and enforcement for RCAs; it is a priority to mitigate that problem so that we can begin to understand why some RCAs are performing better than others.”
CCIRA’s dive survey data were collected when RCAs where just 8-to-15-years-old. Research in California has shown that rockfish recovery was more likely to be detected after 20 years of spatial protection, suggesting that RCAs benefits are likely to keep increasing over time.
4. Marine Protected Areas known to enhance fisheries
Parallel with our work in progress on RCAs, there is growing evidence from other studies conducted all over the world that fish and invertebrates inside Marine Protected Areas (MPAs) can be more abundant and grow to greater size and age than in fished areas. Bigger and older fish can flourish inside well-designed MPAs where compliance is enforced, producing more larvae that disperse to and boost the productivity of nearby areas where fisheries are permitted.
5.What you measure matters
Given what we know about rockfish reproduction, Alejandro is urging Fisheries and Oceans Canada to update their management approach for yelloweye rockfish and other groundfish. DFO’s models focus on overall biomass—the total weight of fish in a population—to estimate the sustainability of fisheries. These models assume that the reproductive capacity of younger, smaller females is the same as that of older, larger females.
This, says Alejandro, is biologically unrealistic given what we know about rockfish reproduction. He suggests DFO should modify their approach to include the restoration of large size and old age classes in yelloweye rockfish populations as explicit management objectives. This is critical as some research suggests that fishery models that focus solely on biomass can underestimate the extent to which stocks have been overfished and promote unsustainable fishing practices.
“Bigger and older fish can flourish inside well-designed MPAs where compliance is enforced, producing more larvae that disperse to and boost the productivity of nearby areas where fisheries are permitted.”