Report on the 2008 Rockfish Survey off Cape Flattery, Washington

In recent years, Rockfish (Sebastes spp.) conservation has become the primary driving force behind management measures for numerous commercial and recreational groundfish fisheries. In coastal waters off California, Oregon and Washington, Canary, Yelloweye and Boccaccio Rockfish were determined to be overfished by the Pacific Fisheries Management Council (PFMC) and within Puget Sound these species have been listed as threatened or endangered by the National Marine Fisheries Service (NMFS).¹ In an effort to promote research to aid in Rockfish conservation, the Washington State legislature passed House Bill 1476 in 2007. This bill, supported by the fishing Industry, created a Rockfish research account for the Washington Department of Fish and Wildlife (WDFW) with funding provided through surcharges on selected commercial and recreational fishing licenses. This funding provided an important opportunity to develop Rockfish research projects to support stock assessments that are intended to inform management and promote conservation of groundfish resources in the Puget Sound basin and off the Washington coast.

In the coastal waters, Yelloweye Rockfish was declared overfished by the NMFS in 2002 and has been one of the main species that limit fishing opportunities. Information for Yelloweye Rockfish collected from the WDFW/ International Pacific Halibut Commission (IPHC) cooperative survey has been incorporated into the PFMC's Yelloweye Rockfish stock assessment since 2001. Unfortunately, the survey catch rate information has varied substantially among years making the population trend information difficult to interpret. In an effort to better understand the fluctuation observed in IPHC survey, WDFW conducted a video survey of IPHC Rockfish stations located off the Washington coast in 2008. The objectives of the survey were to gather data to establish habitat associations and explore catch rates of Rockfish across time and area using ROV survey technology. This information will allow us to develop a more efficient and cost effective way to survey Rockfish populations in areas not accessible to traditional survey techniques while not inducing additional mortality. A long-term no-take monitoring survey program will significantly contribute to Rockfish population status determination. These data will inform stock assessments that will in turn inform fishery managers as they develop effective management measures that provide meaningful fishing opportunity that are in line with conservation of this valuable living resource.

We observed over 2,300 fish from 36 species or species groups, fifteen of which were Rockfish. Rockfish were encountered most frequently and found in the highest density on most transects relative to other species. Among the invertebrates, such as Sea Urchins and feather stars, were encountered most frequently and had highest densities among all other invertebrates. The primary habitat found among transects was gravel with sand as secondary habitat interspersed with boulders that were found in stacked piles or scattered. Many of the Rockfish species including Yelloweye, Rosethorn, SSharpchin/SStripetail grouping, TTiger, Canary, and YYellowtail Rockfish were found largely associated with or near boulder habitat.

Our study suggested that there may be diurnal effects on the relative survey abundance for a number of Rockfish species. For Canary, unidentified juvenile Rockfish, unidentified adult and rosethorn Rockfish, we found higher survey abundance during day light hours compared with nighttime. For Sharpchin/Stripetail Rockfish, we found highest abundance at dawn and dusk. However, due to the low number of observations for many other Rockfish or other groundfish species, it was difficult to draw a conclusion. Yelloweye Rockfish, Tiger Rockfish, Yellowtail Rockfish, Lingcod, sculpin and unidentified flatfish density was variable and without apparent diurnal pattern.

Visual survey methodology has a number of advantages and disadvantages for surveying Rockfish, which have been well chronicled in this study and elsewhere. Some of the disadvantages include: 1) difficulties in fish identification, particularly for small fish or fish with cryptic coloration, 2) the potential for attraction or repulsion from the submersible, 3) variation in detection due to habitat type; for example, due to reduced visibility when the submersible maneuvered off bottom to avoid large boulders, or the failure to detect fish hiding behind boulders, 4) possible bias in collecting length measurements and 5) the limitation of the technique to quantifying the density of benthic species found in close proximity to the bottom. The advantages of the technique include the ability to: 1) sample in habitats that are inaccessible to other survey methods, 2) observe in-situ fish behavior, 3) observe the distribution of fish and fish-habitat associations on a fine scale, and 4) survey where additional mortality is not compatible with conservation for species and/or for species poorly sampled by trawl gear, such as Yelloweye Rockfish.

Given limited funding, expense is a major consideration in developing any groundfish survey. We found that costs associated with this survey were at least five times more expensive than the traditional longline survey methods for surveying the same nine study sites. In the future, however, these costs could be substantially reduced by employing smaller vessels and crew than that used in this survey. This approach has been previously demonstrated to be effective by WDFW which recently completed several small-vessel ROV surveys near the San Juan Islands in Puget Sound. It is unclear how effective this approach would be in coastal waters given more extreme weather conditions and survey depths that are greater than 60 fathoms. If no-take surveys are required, we should consider exploring less expensive ROV survey approaches and/ or other no-take survey methods such as self-releasing pots.

Overall, it is clear that relatively large-scale no-take surveys are needed to assess bottomfish abudance/biomass in habitats that are not accessible to bottom trawl survey gear. This study has demonstrated that visual transect surveys could provide a unique no-take alternative method for estimating Rockfish absolute abundance/biomass in habitats not accessible to conventional survey tools, while setline surveys can only produce relative abundance indices. The absolute abundance/biomass estimates can be used to "ground truth" the biomass estimates in stock assessments; and abundance indices can only "guide" the abundance trends. However, further study among several study sites and habitats will be required to better inform development of survey methods and measure the degree of possible bias associated with diel movement and avoidance behavior. Additionally, research that provides insight into the seasonal and/or social behavior patterns associated with prey or mating will be necessary to fully understand or interpret abundance estimates. Because most groundfish species are habitat-specific in their distribution, careful survey design will be necessary to ensure precise and unbiased estimates of abundance. Specifically, the low density and patchy distribution of Yelloweye and many other Rockfish species must be taken into consideration for developing a meaningful index time series that will be responsive to changes in abundance and useful to population dynamics models. If direct observation surveys such as the present study were conducted on a routine basis, a time-series of Yelloweye Rockfish density data could be used to develop an index of the trend in abundance. Such an index would be indispensable information that could be incorporated into a demographic model of the Yelloweye Rockfish population for stock assessment analysis.

¹ Canary Rockfish were declared rebuilt in 2015 and Bocaccio in 2017.