Rockfish

Sebastes
Photo: Eiko Jones

Rockfish
Sebastes

Of the seventy or so species of rockfish in the Northeast Pacific there are three that are orange in color: canary, vermilion, and yelloweye. In the water column, reds are the first color to fall out as you go deep; it appears gray rather than red or orange to other species at depth.

Old and Grumpy Fish

Rockfish is a generic term for the genus Sebastes, with over 100 species worldwide, with at least 70 of those in the Northeast Pacific. Archaeological sites among the small islands of Barkley Sound on the west coast of Vancouver Island (analyzed in 2014) identified twelve different rockfish species just in that small area. Twenty-eight species are associated with the Salish Sea. The names of the species tend to identify them by color; there are yellowtail and yelloweye rockfish; blue and black and copper rockfish; tiger, canary, red stripe and silverback rockfish. There are also widow, china and quillback rockfish. Though their colors change they all have a broad body with spiny dorsal fins and fleshy downturned lips making these long-lived fish seem particularly old and grumpy.

While some rockfish live in the deeper ocean, rockfish are associated with the kelp forest. This is their home. They are seen as a sign of health or decline of their preferred habitat: the near shore waters in Nereocystis and Macrocystis territory. Some rockfish spend their entire lives at the same site, making a home among the rocks, sea mount cliff faces, and canyons at the ocean bottom. The role of the kelp forest for the lives of rockfish can be detected in the carbon in their flesh. Isotopes can be analyzed to determine whether a fish’s diet is kelp-derived carbon or carbon associated with a fishier diet, i.e. higher up in the trophic web. Interestingly, as rockfish were studied along the west coast of Vancouver in conjunction with healthy kelp forests compared to kelp impoverished sites, the healthier the kelp forest, the less direct kelp-derived carbon is found in their flesh. The explanation is that within a healthy kelp forest, either Macrocystis or Nereocystis, with the associated understory kelps of Pterygophora and others, phytoplankton, larvae, juvenile fish and smaller schooling fish abound. With the added diversity of prey for rockfish, they tend to eat higher on the trophic level, feeding on small fish and crustaceans and larvae who in turn prosper on the algal detritus and nutrients associated with the kelp. 

Old Fish, New Fish

Rockfish can be very old. Depending on their species they can live to be anywhere from 11 to 200 years old. As a long-lived species they take many years to reach maturity, not producing young until they are 20–25 years old. Rockfish eggs are fertilized within the mother’s body and protected there for their first stage of development and then birthed live into the ocean. The thousands of tiny larval rockfish birthed by a single mother depend on the protection of the kelp forests to mature into deeper-swimming, bigger fish. Rockfish can become more and more productive as they age and grow larger. The life cycle of the various species varies but we can look at Yelloweye rockfish for example. These long-lived mothers can carry hundreds of thousands of fertilized eggs, nurturing them internally, and then give birth to live larval young which float as plankton in the open ocean. A large, 7.5 lb rockfish mama can produce 1.7 million young, more than ten times a smaller younger fish.

Rockfish life cycle: rockfish are slow growing and some don’t start spawning at 20–25 years old. As they age the females produce more and more young that are also more robust, gestating the early stages internally for ten months and then birthing thousands of late-stage larval rockfish. These larvae are initially pelagic, but then, finding a home in the kelp forests, develop into juvenile rockfish, and then slowly, into adults.

Human Fishers 

Humans love to fish. They love and need to eat fish, so they pull fish out of the sea for sustenance, and rockfish are generally delicious and nutritious to eat. But rockfish are particularly susceptible to overfishing for these reasons:

  • Their site fidelity means that a certain place can be easily fished out. A diver in British Columbia has photographed the same tiger rockfish at a certain ocean bottom rocky cave over eight years! Their strategy for success depends on long lived reproductive productivity. If those long lives are cut short, populations can decline.
  • Fish are hard to count. To manage fisheries (i.e. how many fish are allowed to be fished out of the waters in a given area) fish need to be counted, but they flit in and out of a transect square—a device used to survey what organisms are within a certain quadrant of area, and this can provide an index of abundance, useful for tracking changes over time, but not a true count of species. How can we really know how many rockfish are there?
  • Their numbers are positively associated with kelp forests, so as kelp forests decline, so do rockfish numbers. Marine Protected Areas, fisheries management plans and regulations, as well as Rockfish Conservation Areas are important tools for helping rockfish populations. MPAs seem to be effective relative to rockfish populations, but many species are still in decline.

But humans also love to pull fish out of the sea for other more spiritual reason, and many anglers are catch and release fishers. When a rockfish is brought up from the bottom too quickly, however, its sealed air bladder, used by the fish to regulate buoyancy, will expand right out of its mouth causing a traumatized fish, and a ghastly sight. This is called barotrauma. The fish must be lowered back to depth carefully to be saved. Despite how we interact with rockfish, they are undeniably an integral part of kelp forests.