Rockin’ with the Rockfish

By Andrew L. Rypel and Peter B. Moyle

Fig. 1. Black rockfish (Sebastes melanops) swimming in giant kelp. Photo credit: Eiko Jones Photography, downloaded from https://www.eikojonesphotography.com/ngg_tag/black-rockfish/

California is a spoil of natural resource riches. Most times, our California waterblog busies itself with important freshwater resources issues. Yet every now and again, it is refreshing and worth turning our attention to the spectacular diversity and mysteries of our Pacific Ocean. But freshwater is important to the ocean too. For one, there are 1,350 km of California coastline, with 100s of streams and rivers dumping nutrients and sediment into the ocean. During geologic times when sea levels were much lower, big rivers helped carve out the rugged underwater topography that is so important for our native marine sea life, including rockfish. And some of California’s most cherished freshwater fishes, such as salmon, steelhead, sturgeon and smelt, divide their time between ocean and river. Some of these adults and subadults will even predate and rely on juvenile rockfishes. Thus, rockfish are a central aspect of the legendary “ocean conditions” so often cited as controlling salmon numbers. Here, we’d like to simply call attention to a fascinating group of marine fishes that have strong interactions with salmon and similar fishes: the abundant, diverse, and beautiful Californians – the rockfishes.

Rockfishes are members of the genus Sebastes, which translates from Latin to “magnificent” or “venerable”. The entire group is comprised of marine species. They are a comparatively young group of fishes dating back 23-34 million years before present (Hyde and Vetter 2007). For comparison, sharks are 450 million years old. Rockfishes range in habitats from the intertidal zone all the way down to ~3,000 m (9,800 feet), making some rockfishes essentially deep sea fishes. By-and-large, they are benthic species that make their living in, on, and around benthic rock outcroppings. Not surprisingly, then, a favorite ‘hangout’ for rockfish (and salmon) is the Farallon Islands, a complex reef system just off the mouth of San Francisco Bay.

There are 109 recognized rockfish species. And while the geographic range of rockfishes encompasses many parts of the globe, the diversity of species is notably concentrated along the Pacific Coast. And California is the direct epicenter of that diversity. Coastal regions of Santa Barbara (the biggest hotspot) harbor up to 60 rockfish species. That’s 55% of all global rockfish diversity! Parts of the coast in northern California (e.g., Bodega Bay) regularly contain 45-55 species.

Fig. 2. Reproduction boom of rockfish at Browning Passage, British Columbia, Canada. Photo credit: Jett Britnell, http://www.divephotoguide.com/underwater-photography-travel/article/underwater-photographers-guide-british-columbia-canada/

Rockfish are a vital component of the California Current Ecosystem. Salmon, lingcod, killer whales, sharks and shorebirds all eat rockfish. There have been anecdotal observations that some of the biggest salmon runs follow years of very high rockfish reproduction. And people of course eat rockfish too. Rockfish sandwiches and tacos are popular seaside fare. Rockfish are also notoriously mislabeled in grocery stores and fish markets – sometimes referred to as “rockcod” or “red snapper” even though that species is native to the Gulf of Mexico.

Their reproduction is on the notably bizarre side for fishes. Rockfish have internal fertilization, high fecundity (number of eggs), and give birth to larval fish rather than laying eggs (aka viviparity). Some rockfish species have fecundities that approach 3M eggs per individual (!). Even for highly fecund fishes, this is high, and again – all those baby fish are born alive. As just one comparison, Tule Perch (Hysterocarpus traskii, another native California live bearer) has fecundities of just 20-60. And finally, female rockfish can store sperm. This allows female fish to engage in reproduction with multiple male mates and utilize stored sperm from males they mated with long ago (Muñoz et al. 2000).

The age and longevity of adult rockfishes can only be described as impressive. While some rockfish species have longevities that approach 20 years, many are notably longer. Species with longevities regularly over 80 years of age include the yelloweye rockfish (Sebastes ruberrimus), the darkblotched rockfish (Sebastes crameri), splitnose rockfish (Sebastes diploproa) and the rosethorn rockfish (Sebastes helvomaculatus) (Love 2002). A 205 year old rockfish was recently captured in Alaska. This individual (that was only recently captured) was apparently born in 1808, five years after the Louisiana Purchase.

Despite the long-lived ecology and life-history described above, rockfish do support commercial and recreational harvest fisheries in California. However, populations are notably vulnerable to effects of fishing and have a tendency to be serially over-harvested in the absence of science-based fisheries management (Wetzel and Punt 2016). On the commercial end, rockfishes are managed as “groundfish”. This classification includes rockfishes, but also flatfishes of various types and other fishes, like the lingcods.

Recreational fisheries management for rockfish in California is tricky. One of the hardest aspects of this challenge is that many rockfishes are exceedingly difficult to distinguish, even by the experts. For example, here are two quotes by Butler et al 2012. that illuminates the crux of the challenge:

“Even today, after a collective century of experience, one or another of the authors will pass around a crisp, sharp image of some rockfish peeking out of a crevice, or worse, just sitting right out in the open, and we will all agree that we don’t know what species we are looking at. Oh, we will have our theories. And we will back it up with chatter about the number of pectoral fin rays, or the absence of some blotch or smudge on the back or head, or the shape of the spine under the eye. But really, after all of this time working on these animals, when we view these fishes underwater, we are still sometimes mystified.”

“The ~84 species of scorpaenid fishes (i.e., rockfishes, thronyheads, and scorpionfishes) inhabiting the northeast Pacific help insure that the lives of many fish biologists will be exercises in decades-long humility.”

Ultimately, when even the experts struggle with field identification, you can’t reasonably expect anglers and fishers to be equally or better skilled. As such, California’s recreational fishery is mostly managed via aggregate bag limits (i.e., rockfish species are grouped together). The season is open year-round to shore anglers, but restricted to march-December for boats, presumably to protect large fecund females on spawning grounds. However, the regulations do require anglers to know how to identify some of the more obvious species, including the long-lived ones. This includes yelloweye rockfish, bronzespotted rockfish, and cowcod.

Barotrauma is another concern (Parker et al. 2006, Jarvis and Lowe 2008). Given the depths at which rockfish reside, when fish are quickly brought up from depth they are quickly decompressed, which expands the gases in their swim bladder. Fish released with inflated swim bladders (often expelled out of their mouths) cannot resubmerge and will die. Deepwater release or descender devices assist in recompression of fishes like rockfish such that they can be released safely. A recent study in Alaska found that survival of yelloweye rockfish (one of the more long-lived species) was 98% when released using descender devices; however only 22% of fish released at the surface survived. Descender devices are not mandatory in California, but many anglers do use them and are encouraged to do so. All things considered, these seem like reasonable fishing regulations for a group of fishes that present some significant challenges to management.

Fig. 3. Global map of Marine Protected Areas (MPAs). Roughly 6.4% of global ocean habitat is covered by protected areas and only 1.9% is exclusively no-take. Image from https://www.iucn.org/resources/issues-briefs/marine-protected-areas-and-climate-change

Marine Protected Areas or MPAs appear to be another useful tool. Numerous studies have been published on the potential benefit of MPAs on marine fish stocks, notably rockfishes (White et al. 2010; Nickols et al. 2019). Incidentally, MPAs also serve as a good model for considering how to propose and manage freshwater protected areas. Evidence of the benefits of MPAs is apparently so overwhelming that the American Fisheries Society (the principal scientific organization concerned with the study of fishes and fisheries in the USA and North America) issued a policy statement on management of Pacific rockfish (Parker et al. 2000). In the statement, the society recognized the need for conservation and robust management of Pacific rockfishes due to their low population growth rates, status of many populations as overfished, and the complex nature of mixed commercial and recreational fisheries. The also state:

“The AFS supports the establishment of systems of Marine Protected Areas to protect the habitat of Pacific rockfish and to promote the recovery of stocks. Such areas should be established along with traditional management measures to control fishing mortality. Regardless of the management strategy used, substantial decreases in fishing mortality must be achieved soon to avoid stock collapse.”

So in summary, rockfish are an extremely interesting and unique California resource. A number of fundamental ecological questions arise from just the limited information covered in this blog. For example: How do all those rockfish species coexist? What is it about California and the Santa Barbara region that has given rise to such speciation of rockfishes? Why are there 96 rockfish species in the north Pacific Ocean and only 2 in the north Atlantic Ocean? What is the relationship between rockfish abundance and that of salmon and steelhead? And finally, how can we conserve and manage these populations for future generations of Californian’s to enjoy?

Andrew Rypel is an Associate Professor and the Peter B. Moyle and California Trout Chair of coldwater fish ecology at the University of California, Davis. He is a faculty member in the Department of Wildlife, Fish & Conservation Biology and Co-Director of the Center for Watershed Sciences

Peter B. Moyle is a Distinguished Professor Emeritus in the Department of Wildlife, Fish & Conservation Biology at the University of California, Davis and Associate Director of the Center for Watershed Sciences.

Fig 4. Blue rockfish (Sebastes mystinus) Blue rockfish off Cannery Point, photographed off of Point Lobos State Natural Reserve, CA. Photo Credit: Daniel Williford, downloaded from Wikicommons.org

Further Reading

Butler, J.L., M.S. Love, and T.E. Laidig. 2012. A Guide to the Rockfishes, Thornyheads, and Scorpionfishes of the Northeast Pacific. University of California Press.

Hyde, J.R., and R.D. Vetter. 2007. The origin, evolution, and diversification of rockfishes of the genus Sebastes (Cuvier). Molecular Phylogenetics and Evolution 44: 790-811.

Jarvis, E.T., and C.G. Lowe. 2008. The effects of barotrauma on the catch-and-release survival of southern California nearshore and shelf rockfish (Scorpaenidae, Sebastes spp.). Canadian Journal of Fisheries and Aquatic Sciences 65: 1286-1296.

Love, M.S. 2002. The Rockfishes of the Northeast Pacific. University of California Press.

Love, M.S. 2011. Certainly More Than You Want to Know About the Fishes of the Pacific Coast: A Postmodern Experience. Really Big Press.

Muñoz, M., M. Casadevall, S. Bonet, and I. Quagio-Grassiotto. 2000. Sperm Storage Structures in the Ovary of Helicolenus dactylopterus dactylopterus (Teleostei: Scorpaenidae): an Ultrastructural Study. Environmental Biology of Fishes 58: 53-59.

Nickols, K.J., J.W. White, D. Malone, M.H. Carr, R.M. Starr, M.L. Baskett, A. Hastings, L.W. Botsford. 2019. Setting ecological expectations for adaptive management of marine protected areas. Journal of Applied Ecology 56: 2376-2385.

Parker, S.J., S.A. Berkeley, J.T. Golden, D.R. Gunderson, J. Heifetz, M.A. Hixon, R. Larson, B.M. Leaman, M.S. Love, J.A. Musick, V.M. O’Connell, S. Ralston, H.J. Weeks, and M.M. Yoklavich. 2000. Management of Pacific Rockfish: American Fisheries Society Policy Statement Fisheries 25: 22-30.

Parker, S.J., H.I. McElderry, P.S. Rankin, and R.W. Hannah. 2006. Buoyancy regulation and barotrauma in two species of nearshore rockfish. Transactions of the American Fisheries Society 135: 1213-1223.

Wetzel, C.R., and A.E. Punt. 2016. The impact of alternative rebuilding strategies to rebuild overfished stocks. ICES Journal of Marine Science 73: 2190–2207.

White, J.W., L.W. Botsford, E.A. Moffitt, and D.T. Fischer. 2010. Decision analysis for designing marine protected areas for multiple species with uncertain fishery status. Ecological Applications 20: 1523-1541.

This entry was posted in Uncategorized. Bookmark the permalink.

Leave a Comment (moderated)

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s