ROCKFISH

Fig. 1 Yelloweye rockfish

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To Pacific fishermen they're knownas snappers, canaries, greenies and

rock salmon, but collectively they'recalled 'rockfish" or "rockcod". Thename "rockcod" is a misnomer, sincethese fish are not at all related to the truecod. In British Columbia waters thereare 36 known species of rockfish belong­ing to the family Scorpaenidae, whichin turn is represented by 34 species ofthe genus SEBASTES and two of thegenus SEBASTOLOBUS.

Although the geographic range isdifferent for each species, rockfish maybe found in the North Pacific Oceanfrom southern California to KyushuIsland (Japan), and in the North Atlan­tic from Georges Bank to the North Sea.The majority of the species inhabit thecontinental shelf and upper sloperegions, and consequently are some­times described as "shelf" and "slope"rockfish. While each species existswithin a specific depth range, rockfishcommonly occur at a wide range ofdepths, from kelp beds in the intertidalzone down to 900 m below the surface.Rockfish are primarily bottom species,although a few (yellowtail and widowrockfish) spend at least part of their timein midwater .

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Rockfish are distinguished by theirstout, heavy build. Large, broad heads,usually bearing spines and strong ridges,and heavily-spined fins are notable fea­tures. The colour patterns vary greatlyamong species and range from black anddrab green through brilliant orange andcrimson, and some are accented by thepresence of wide red or black verticalstripes.

BiologyThe two species of SEBASTOLOBUS

are egg layers, depositing their eggs intransparent, gelatinous masses whichfloat at or near the surface, while theSEBASTES group bear live young(larvae). The reproductive cycle forSEBASTES basically consists of threephases: insemination (transfer of spermto the female), fertilization, and partu­rition (release of larvae). In general,females are inseminated during theautumn months but actual fertilizationof the eggs take place in winter or earlyspring. The eggs develop into larvaewhich are approximately 6 mm at thetime of release. Time of parturitionvaries considerably among areas andspecies, but the majority release theirlarvae sometime between Januaryand May. An adult female rockfish(SEBASTES spp.) may release 200,000to 800,000 larvae, depending on thespecies and size of the female.

During the first stage of developmentthe larvae are pelagic and presumablylive near the surface for some timebefore settling to the bottom. Duringthis early (planktonic) stage, rockfishare not easily identified by species. It isnot until the larvae evolve into juvenilesthat they begin to differentiate anddevelop the morphological characteris­tics of the adult. For some species, thecoloration of the juveniles, when theyare about 10 cm, may be similar to thatof the adult stage. Others, like thejuveniles of the yelloweye rockfish, arequite different from the adult, and wereat one time considered to be separatespecies.

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Fig. 2 Canary rockfish

Fig. 3 China rockfish

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There is little information availableabout the migration patterns of rock­fish. They are considered to be anon-migratory species with localizedmovement only, although there are indi­cations that some species undergo sea­sonal depth migrations. Some speciesform large schools while others aresolitary and hide in crevices.

Rockfish eat a variety of foods includ­ing herring, sand lance, crabs, shrimpand euphausiids. They are considered tobe opportunistic feeders that will takewhatever food is available ilt the time.

Recent advances in age determinationtechniques have revealed that rockfishas a group are long-lived and growslowly. Several species have beenrecorded to be older than 70 years andone rougheye rockfish was estimated tobe 136 years old. Most of the species donot reach commercial size until they areeight to II years of age (approximately30 to 35 em). Adult rockfish range insize, depending on the species. from15 em for the pygmy rockfish (S. wilsoni)to 100 em for the shortraker rockfish(S. borealis). The average size of mostcommercially important species rangesfrom 35 to 50 em.

Males generally reach sexual maturityat an earlier age than females of thesame species, and adult females areusually larger than males of the sameage. The age at first maturity (age atwhich 50 per cent of the fish are firstmature) ranges from two years for femalePuget Sound rockfish (S. emphaeus) toapproximately 18 years for femalecanary rockfish (S. pinniger).

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Fig. 4 Copper rockfish

Fig. 5 Tiger rockfish

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The FisheryHigh opening otter trawls are the

most common gear used to catch rock­fish in the commercial fishery. Manyrockfish species are caught, although atpresent only eight have any substantialcommercial value. Some quantities ofrockfish are also taken by sport fisher­men who usually jig or troll for themalong rocky reefs and near kelp beds.

Pacific ocean perch has historicallybeen the most valuable of the rockfishspecies to both domestic and foreignfleets fishing in Canadian waters. Otherrockfish species have been exploited byU.S. vessels since the mid 1960s, and byforeign fleets since the latter 1960s whenPaci fic ocean perch stocks began todecline in areas of previous abundance.By contrast, Canadian fishermen didnot begin directed fishing for thesespecies until the mid 1970s.

Foreign fleet activity in Canadianwaters, primarily from the SovietUnion, Japan and Poland, began in1965 and peaked during its initialonslaught (1965-1967) removing an esti­mated 102,000 t. By 1970, the rockfishcatch and effort of the foreign fleet haddecreased by more than 80 per cent.With the advent of the 200-mile limit in1977, quotas were set by Canadian fish­ery managers to protect the major off­shore rockfish species. In 1978 theforeign fleet, which by then consistedonly of Japanese trawlers, ceased to fishfor rockfish in B.C. waters, and theU.S. trawl fleet has not fished inCanadian waters since April, 1981.

Most of the rockfish caught by thedomestic commercial fleet is filleted,packaged for freezing and exported tothe U.S., Japan and Europe. A limitedamount goes to the local fresh fishmarket.

Over the past several years the marketfor rockfish has gradually expanded withthe landed value per pound doublingsince 1970. The steadily increasingdemand for rockfish was reflected in itsincreased value. In 1980, rockfish wereworth (wholesale) more than ninemillion dollars (landed value ­3.1 million).

Fig.6 Olter trawler bringing in rockfish

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Further Reading:Hart, J.L. 1973. Pacific Fishes of

Canada, Fish Res. Bd. Can. Bull.No. 180.

Eschmeyer, W.N. Earl S. Herald,Howard Hammon. A Field Guideto Pacific Coast Fishes of NorthAmerica 1983.

Text:Dick NagtegaalFisheries Research BranchPacific Biological StationNanaimo, British Columbia

Underwater World factsheets are briefillustrated accounts of fisheriesresources and marine phenomena pre­pared for public information and edu­cation. They describe the life history,geographic distribution, utilization andpopulation status of fish, shellfish andother living marine resources, and/orthe nature, origin and impact of marineprocesses and phenomena.

Others in this series:American EelAmerican PlaiceAmerican SmeltArctic CharrArctic CodAtlantic CodAtlantic GroundfishAtlantic HalibutAtlantic HerringAtlantic MackerelAtlantic Pelagic FishAtlantic SalmonAtlantic ShellfishAtlantic Snow CrabCapelinCrabs of the Atlantic CoastDungeness CrabGrey SealHaddockHarbour SealHarp SealHooded SealIrish MossLake TroutLingcodLobsterLumpfishMarine Fish Eggs and LarvaeNorthern ShrimpOysterPacific HerringPacific SalmonPollockRedfishRed HakeRed TidesRoundnose GrenadierSand LanceSea ScallopSelected Freshwater FishSelected Shrimps of

British ColumbiaSoft-Shell ClamSpiny DogfishThorny and Smooth SkatesTurbot (Greenland Halibut)White HakeWinter FlounderWitch FlounderYellowtail Flounder

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Underwater World

Published by:

Communications DirectorateDepartment of Fisheries and OceansOttawa, OntarioKIA OE6

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DFO/2106 UW/51

Minister of Supply and ServicesCanada 1985Catalogue Number Fs 41-33/51-1985£ISBN 0-662-14043-5

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