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Rare success at rearing native California rockfish

Lab fish celebrate first birthday

By Christina S. Johnson, California Sea Grant

One-year-old brown rockfish reared in the laboratory of Peter Collins, UC Santa Barbara. These fish are about 12 centimeters long and weigh about 33 grams. Photo: Anastasia Schwab

A 1-day-old brown rockfish (top) is about 5 mm long. This 1-day-old white seabass (bottom) is about 2.5 mm. Rockfish are viviparous, which means females give birth to live (tiny) fish. Most fish including the white seabass are oviparous, meaning eggs are laid by females and develop outside the body. Photos: H. Fukui and P. Chaille, UCSB

Seabass are faster growing than rockfish (top) so that by 17 or 18 days of age, the seabass (bottom) is (even to the untrained eye) obviously more developed and heartier. Photo credits: Day 17 rockfish: H. Fukui and Chaille, UCSB; Day 18 seabass: Hubbs-SeaWorld Research Institute

UCSB biologists Peter Collins (left) and Hisaya Fukui (right) Photo: H. Fukui and P. Chaille, UCSB.

Raising fish is a tedious, labor-intensive process. The Collins lab relies on help from undergraduate volunteers like Anastasia Schwab pictured above. Not pictured is undergraduate volunteer Jennifer Dang. Photo: P. Chaille, UCSB

After more than a decade of studying rockfish reproduction, growth and development, California Sea Grant biologists have successfully reared brown rockfish from birth through their critical life stages. The achievement is significant because rockfish, more than other fish, have fragile and complicated early life histories. They are also prone to overfishing and hence have been a priority for fisheries management.

The ability to raise the fish in captivity, scientists say, adds significantly to what is known about the species' early growth and development. It also opens the door to the possibility of rearing rockfish for release in the wild to boost depleted stocks. Eventually, it may even be possible to farm rockfish for human consumption, as is currently done with much success in places such as Japan and Korea .

Endocrinology professor Peter Collins and research biologist Wai Ning Tsang, both at the University of California , Santa Barbara , attribute the lab's rare success in rearing native rockfish to two factors. One was the ability to carefully control environmental conditions, such as temperature, water quality and light. Nutrition was also a critical factor. Much of the lab's success hinged on the discovery by graduate student Hisaya Fukui that brown rockfish larvae need to be fed organisms they would eat in the wild.

"We shifted from feeding larval rockfish 'convenience foods,' that is micro-organisms that can be readily raised in the laboratory, to a natural diet, which more closely resembles the diet larval rockfish would encounter in the wild and which has been nutritionally optimized to enrich growth," Collins said.

Brown rockfish are one of more than 100 nearshore rockfish species (most of which are in the genus Sebastes) that inhabit the various rocky and sandy habitats associated with kelp forests and reefs. Brown rockfish, commonly referred to as bolina by fishers, live in shallow subtidal waters and bays associated with the interface of rocky and sand areas. Like most rockfish, they are prone to over-fishing and slow to recover once depleted.

Collins, in fact, originally received California Sea Grant funding to study rockfish reproduction and fecundity to provide information that might help state biologists develop a legislatively-mandated nearshore fisheries management plan. With the lab's newfound success in rearing rockfish, their attention is now turning to the possibility that mild-tasting, high-value rockfish might also be candidates for aquaculture.

The size of the brown rockfish swimming in the tank in the Collins laboratory illustrates why managing rockfish stocks has been such a challenge and priority – and why culturing them is equally daunting. Among the group of nine brown rockfish that recently celebrated their first birthday, the biggest fish is 12.6 centimeters and weighs 33 grams. This contrasts starkly with the aquaculture star cobia, which bends the scales at six kilograms after a year of culture.

The UCSB researchers, however, believe that innovative husbandry techniques might spur growth rates and thus open the potential for rockfish aquaculture or stock enhancement.

Mike Rust, the team leader of a marine enhancement program at NOAA's Northwest Fisheries Science Center in Seattle whose group has reared several species of rockfish, including browns, agreed: "We don't know whether the fish are slow growing because of inherent biology or because they don't eat often in the wild. If we knew what to feed them, they might grow a lot faster."

The growth rates of black rockfish cultured in Asia offer a promising example. Black rockfish growth has been increased 250 percent through diet.

Former Sea Grant Trainee Peter Chaille, a graduate student working in the Collins lab, is also optimistic about the potential for culture one day. "First you have to know how to grow them normally," he said. "Then there is the potential to accelerate their growth."

"This research is a starting point for establishing a complete picture of the way brown rockfish grow and the effects a suite of environmental changes could have on their growth," Chaille said. "We are just in the early stages of understanding rockfish culture."

6/12/06

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