FLATFISHES: A Systematic Study of the Oregon Pleuronectid Production System and Its Fishery

Andrew G. Carey, Jr. Robert L. Demory William G. Pearcy Sally L. Richardson Albert V. Tyler Charles E. Warren

by Charles Jackson

OREGON STATE UNIVERSITY SEA GRANT COLLEGE PROGRAM AdS 418 Corvallis, OR 97331

ORESU-T-81· 001 $2.00 Acknowledgements

The Oregon State University !is Sea Grant College Programis supported cooperatively by the National Oceanic and Atmospheric Administration, U.S. Department of Coneerce, by the State of Oregon, and by partici pating local governmentsand private industry. The OSUSea Grant College Program attempts to foster discussion of important marine issues by publishing reports, sometimesdealing with controversial materials A balanced presen- tation is always attempted. Mhenspecific views are presented, they are those of the authors, not of the Sea Grant College Program, which does not take stands on issues.

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Sea Grant Ceenunications Oregon State University Administrative Services Bldg., Rm. 418 Corvallis, OR 97331 03! 754-27]6 Please include author, title and publication number. Some publications carry a charge to help defray printing expenses. The charge, if any, appears after the publication number. Please make checks payable to Oregon State University. CONTENT

~Pae Figures 5 Tables ...... iv

Section l, Introduction and Background ...... ~ . 1

Section 2. Description of Study ...... 7

Section 3. ReSU1'tS 4 ~ ~ ~ ~ 4 ~ ~ ~ ~ ~ ~ 4 ~ ~ ~ ~ ~ ~ 1 7

Appendix ~ ~ ~ ~ ~ ~ 4 ~ ~ ~ ~ ~ ~ 4 ~ ~ ~ ~ ~ ~ FIGURES 8r.TABLES

Table 1 ...... 10 Figure 3-3 ...... ~ ...... 24 Data requirements for R/OPF-1 Parallel trends between upwelling subprogects and growth rate increments for Dover sole Figure 2-1..... ~...... 11 Figure 3-4 ...... , 25 Flaw of R/OPF-1 subprojects Changes in seasonal growth increment for English sole with Figure 2-2 ...... 12 bottom temperature Chrono1ogy of subprojects investigating the distribution of Figure 3-5 ...... , . . . 28 flatfish stocks and associated species Portion of food web off Oregon and Washington showing direction of Figure 2-3...... 13 food-energy flow for English sole ChronoIogy of subprojects and associates investigating the productivity of the bottom-dwelling phase of the Figure 3-6 ~ ~ e ~ ~ a ~ ~ 4 0 0 ~ ~ ~ ~ flatfish life cycle Computer maps of Oregon catches for English sole Figure 2-4 ...... 14

Chronology of subprojects Figure 3-7 ...... 29 investigating the productivity of the water coIumn-dwel1i ng phase of Computer maps of Oregon catches the flatfish life cycle for Dover sole

Figure 2-5... 15 Figure 3-8 ...... 31 Chronology of subprojects Variation in quota necessary for attempting to synthesize relationships maximization of yield for the between flatfish productivity and Dover so1e stock off northern fisheries Oregon and southeastern Washington for the period 1946-1962 Figure 3-1...... 22 Figure 3-9 ...... ~ ...... 32 Simulated and observed spawning times for English sale Fish assemblage maps for the continental shelf off Oregon Figure 3-2 ...... ~ . ~ . . . . . 23 Figure 3-10 ...... 33 Year-class strength of Dover sole estimated by cohort analysis Assemblage composition along a compared to estimates based on transect east to west farm points environmental variables between Cape Heares and Cascade Head 1. INTROGGCTION 6 BA K GND

P 1euronecti ds--sa1 twater fl atfi she s--make up a significanN: fraction of Oregon's trawl f i sheries. [Pl euronecti ds, according to Webster ' s thir 4 unabri dged dictionary, are flatfi shes order Heterosomata! that have

extending well forward on the head, and the mouth terminal.] Oregon's Department of Fish and Wildlife ODFW! keeps count of more than 13 species of flatfishes landed comnercially fram state and adjacent waters. Dover, English, and petrale sole make up the greatest poundages and con+and the highest ex vessel prices. In 1979 flatfishes* accouMneif Vor about 43 percent by weight! of al1 traw1 landings and approximately $6.18-million, or 30 percent by value!, of the state's total groundfish catch.

The number of trawl er s including shrimp trawlers! licensed by the State of Oregon has grown geometrically in recent years. DDFWrecords show 52 Oregon and out-of-state boats licensed for all trawl fisheries in 1952. 65 ten years Tater, 93 in 1970, 124 fn 1975, and 280 by 1979! Their quanti+ alone does n~o tell the entire story. l hile the number of trawlers has been rising ever faster, the typical new boat may be up to twice the length of its predecessor, with proportionally greater fishing capacity. For heavi'Iy exploited flatfish stocks. this trend points up urgent need for refining fisheries managementcapabilities.

From the earliest days, trawl fisher- men and biologists have recognized that distributions of flatfishes and other species overlap on Pacific Northwest

*Excluding halibut, which may not be taken legally by net under international regula- tions but inc ludes sanddabs af the Fam. Bothidae fishing grounds. Although the trawl fleets unless the unregulated foreign pressure was direct their efforts toward the most mar- curtailed, it cnuld and would cut tradfonal ketable species, trawling as a fishing domestfc catches. In 1976 the United method captures a mfxture of species that states unilaterally asserted sovereign varies in sfzes and ages. Tr awlers discard claim to the economic resources of its undersize and unsaleable fish overboard. continental she'If. This political i nitfa- Few survive. tive redressed a measure of American fish- ing industry 's concern. However, the Fishery Conservatfon and ManagementAct has come to be regarded internationally as "The number of travelers enlightened leg5slatfon. Specifically, it encourages global use of ocean production, licensed by the State of while reserving for U S. fishermen and Oregon has grocen processors the ffr st rights to ocean stocks geometrically in recent within the 200-mile economic zone. Perhaps more noteworthy in the eyes of its critics years." is what the Act omits--it does not exclude foreign fishing inside the zone, despite lobbying by fishermen for such a ban. As consumer demand for seafood rose Instead, it legftimfzes the lfcensing of during the 1960s and '70s, socfal and forefgn vessels subject to American regu- politica1 pressures mounted to manage fish lation! to harvest surplus production not stocks to perpetuate maximum harvest taken by U.S. operators. In sum, then, the capabilities. Fisheries management is a Act imposes a political solution to social relatively youngconcept, mostly postdatin~ and biological problems. It creates man- world War II. Owing to ocean fishes agement goals such as "optimum sustainable elusive behavior and the opaque, three- yields" OY! but delegates definitfon of dimensional, fluid nature of their habitat, such crucial concepts to managementagen- pfoneering ffsheries scientists have had to cies. The Act thus provides a new urgency deal with one cryptic variable at a time. for fisheries Scfentfsts to advance from Nonetheless, the knowledge thus derived has analyses of historfcal changes in produc- enabled researchers to begin pfecing tivity to bona fide pr edictive capabil- together a functional understanding of itiess. crftical aspects of fisherfes productivity and human exploftation of marine stocks.

Investigators fn the Pacific Northwest "Perhaps more have been stockpiling catch and effort sta- noteworthy in the eyes of tistics and bfologfcal data for 25 years. its critics is cehat the Their research has linked fluctuations in key fi sherfes with variations in physfcal Fisheries Consereation and biological factors in the fishes ' and Mafu~ement! Act environment. By the early 197Os, with omits-it does not public access to remote sensing data and the advent of third-generation computing exclude foreign fishing technology, some fisheries scientists were inside the 00 mile! zone, coming to belfeve that the majority of despite lobbying by fisheries dynamics wi11 not be adequately explicable without considering multiple, fishermen for such a interdependent factors. That is to say, ban." they began to advocate studying fisheries dynamics as a system of interactive variables. From six to ten investigators at Oregon State University had been working Meanwhi1 e, spiral 1 ing demand for independently on aspects of ocean produc- seafood prompted growth of local fishing tivityy with Sea Grant funding since 1968. fleets. It compelled foreign operators to In spring 1974 grantees fn OSU's Department range ever farther to sea. Russian of Fisheries and Wildlife and School of trawlers first appeared in Oregon waters fn Oceanography drafted proposals to extend 1966. Their intrusion onto prevfously their prfor research. '0th encouragement uncontested domestic fishery grounds esca- from the Sea Grant director and logistical lated fishing effort in the northeast aid from Sea Grant' s marine advisory Pacific and aggravated Americans. Most of agents, they participated in informal meet- the U.S. industry was of the opinion that ings in coastal contuunfties. There and

OSU Sea Grant administrators did not 6! evaluating the growth rates of juve- venture into this rmrltiple-year, inter- nf'le English sole in estuarine and disciplinary funding caamrifiaent without nearshore nursery areas; reservations. Against prospects for use- ful, readily acceptable findings they had 7! analyzing loss in flatfish yield to weigh the risks of coming to inconclu- caused by discarding undersize speci- sive endings and failing on a grand scale. mens from trawl catches; The National Sea Grant Program's amenabil- ity to flexible programming encouraged them e! discovering that flatfishes in the to proceed. The project has subsequently study region grow faster as water tem- capitalized on adaptability- As Section 2 perature drops, ~hich fs the inverse of docueents, the study has seen certain sub- teaqrerature's effects on growth of North tasks substantially revised, resources Atlantic flatfish stocks; redirected, some inquiries closed, and others opened, and one or two efforts come deeonstrating statistica11y that to dead ends. The mixing of disciplines upwel1 fng i s a dominant determining and need to be adaptable combined at times influence on survival of flatfish lar- to frustrate program administrators. vae and growth of juvenile flatfish; Nonetheless, by June 1980 the project clearly had begun illumining bow flatfish 10! di scoveri ng a long-term trend in reproduction and growth processes affect upwelling that is a doeinant influence flatfish productivity and how domestic on biological productivig in the fisheries use that productivity. region;

Section 3 digests technical accoe- linking fluCtuations fn flatfish popu- p'lisheents through June 1980. One ten- 1 ations to natural var f ati ons in tative conclusion is that Oregon pleuro- oceanic conditions demonstratfng that nectids offer a potential for greater flatfish productivity varies indepen- productivity if managed as assemblage dently of ffsherfes effort!; units. Trawls do not captur e a single target species, but take sections of entire 12! analyzing fleedf ng sel ec tivi ty of and bottoe coaInunf ties. The fishes in these the fnfluenCe Of bOttOm sediments and coaIaunities interact to significant food on the distribution and abundance degrees. In the pleuronectid fisheries, of Dover sole; therefore, it appears that it is not possible to manage for maximum productivity 13! analyzing fIhe food web of represen- of more than one species fn a stock at a tative f1atffshes and associated spe- time. Furthermore, evidence from this pro- cies to determine which Compete for ject suggests that using traditfonal yield food and form interactive species models to manage species that interact in associationS that should be managed as assemblages wi'll not lead to long-term sta- a group; bility in the fisheries. 14! 'developing computer software for esti- R/OPF-1 resu'its to date include: matfng broad strengths of represen- tative species five years 1ater at 1! developing coeputer software to ana- age of recruitment! from current data 1yze species associations and ana- on upwelling; lyzingg the species associations fn which the coneercfally valuable flat- 15! proposing that calculation of maxieum fishes occur; achievable yields for one flatfish Specfes requfreS data on six to ten 2! mapping coaiaercial catch locations; species;

3! mapping seasonal shifts in catch pat- 16! determinf ng from stati stics for the terns and relating those migrations to early 1960s and 1970s that calculation spawning behavfor; of fl atfi sh catch quotas by tradi- tional methods would have damaged 4! developing computer software to local stoCks had not economic portray commercial catch statistics as constraints curtai'led markets; "three dimensional" graphics; 17! proposing that managing one flatfish 5! locating near shore nur sery grounds species in an association for maximum that are at feast as important to pro- productlvfQ precludes achfevfng maxi- ductivityy as estuarine areas for cer- ma productfvfty for other species in tain species; that assocfdtfon; 18! proposing that an al ternative mul tiple-species fishery stategy should be to optimize productivitg of selected species and maintain species population levels i%thin associations and not to attempt to optimize yields oT all species!,

19! demonstrating that stock size had 1 i ttl e effect on resulting brood strength for a 25-year period; and

20! determining that establishment of fisheries strategy for flatfishes requires choosing either constant yield or maximumproductivity which fluctuates with variability in oceanic conditions!.

R/OPF-1 investigators speculate that of al 1 their findings the feeding studies may be of greatest long-term value. To continue work on the feeding studies, synthesis of results from the various subprojects, and documentation of findings, the Sea Grant program has extended support for portions of the project through June 1981.

Project R/OPF-1 has been administered by Oregon State University 's Sea Grant College Program with funding from the State of Oregon and the National Sea Grant College Program, National Oceanic and Atmospheric Administration, U.S. Department of Conwnerce. This work has been supported by federal grants 04-7-158-44085, 04-8-H01- 144, and hlA79AA-000106.

2. DESCRIPTION OF STGDY

Project 1/UPF-l, the Pl euronecti d Production System and Its Fishery, consti- tutes applied research. In part it is a response to requests from local fishing industry, which the project's principal investigators interpreted as indicative of need for a holistic study of the dynamics of the cNmaercial ly important fl atf i sh stocks off Gregon.

The primary target species of the Oregon pl euronectid fi shery are Dover, English, petrale, and rex sole. Landings of each of the sole species annually amount - to millions of pounds. The area for this study extends essenti al ly from southern washington to Cape Blanco and seaward to the margin of the continental shelf.

Another influence on the focus of the study was availability of pertinent research data previously collected by the Oregon Department of Fish and Ii ldlife, USU Sea Grant, OSU School of Oceanography, and other entities active in fisheries research in the northeast Pacific. The predecessor agency to DDFH had gathered data on age-class structure of sever al flatfish species. including estimates of biomass, growth and mortality rates. In addition to those data, Sea Grant and DUFF personnel had some informatfon on the distribution of bottom dwe11ing fishes relative to water depth arid types of bottom sediments, on food habits of flatfishes, and on distribution of flatfish larvae.

Yet another stimulus was the high pr i or i ty accorded thi s research by the Pacific Marine Fisheries Commi ss ion and OUFw. Fisheries managers foresaw a need for better understanding of flatfish pro- ductivi ty in anticipation of U. S. extension of its economic zone beyond the then 12-mi 1 e 1 imi t. More ef fecti ve management of flatfish stocks off Oregon would require a better informational base than existed at that time.

Flatfishes harvested by trawl are taken in associations with other types of bottom fishes and with other sea-floor ficient to maxiimize production and avoid organisms. One of the important objects of overfishing became-timely questions. the study has been investigation of the biological significances of associations to The project's systematic study of f'latfish productivity. Unknowns when the f1atf i sh productivi ty, wi th its impl i ca- project was designed included: which spe- tions to the fishery, reflects the combined cies in the association of fishes feed on breadth of skills offered by the sir senior the Same prey; ~hiCh SpeCieS prey On flat- investigators. These six were. fishes, and in what phases of the fl atfi sh life cycle; which foods flatfishes prefer Andrew G. Garey, Jr. in the various phases of their life cycle; Biological Oceanographer and how much of this food is available. USU School of Oceanography

There were gaps in understanding of Robert L. Demory the critical stages of the flatfish life Aquatic Biologist cycle. All species hatch from egg into Oregon Dept. of Fish and Wi ldlife planktonic larva and drift with currents in the water column. The larva metamorphoses William G. Pearcy to fish form, settles to the ocean bottom. Bi oloqical Oceanographer and acquires the physical characteristics OSU School of Oceanography of flatfishes, including migration of one eye to what becomes the darker, "dorsal" Sally L. Richardson surface. Juveniles mature over a span of Biological Oceanographer three to eight years. Recruitment to the OSUSdhool of Oceanography fishery occurs bet~can the third or fourth and the ninth years. The natural life span Albert V. Tyler runs to about 20 years for Dover sole, Fisheries Ecologist which is comnon for northeast pacific spe- OSU Dept. of Fisheries cies. and Wildlife

Growth and survival are processes Charles E. Warren critical to fish production and fishery Aquatiic Ecologist yields. Data on both processes were VSU Dept. of Fisheries scarce. Estuaries were known to serve as and Wildlife important nursery areas for juvenile English sole and starry flounder, but in Richardsori's ability to identify flat- 1975 no one had evaluated how critical the fish larvae was indispensable ta answering role of estuaries might be to maintenance questions aboult the larval phase of the of flatfish populations. Also, the food pleuronectid li'fe cycle. Earlier Sea Grant web of flatfishes had received but limited work by Pearcy and Carey had dealt with research attention. Fisheries scientists bottom sediments' characteristics that intuitively linked oceanic variables caused affect flatfishes and bottom-dwelling by upwelli ng to locally high fish produc- invertebrates. These studies provided a tionn, but na one had scientifically basis for probting flatfish feeding habits demonstrated such relationships. However, and availability of food. Oemory's study other workers had found that sea-surface of the distributions of flatfishes from temperature and transport of larval English UDFW reSearCh Crui SeS gaVe the team an sole by ~ater mass influenced brood abun- empirical basiS for its planning and pro- dance outside the upwelling region. Ref. vided the inittlal data for analyzing spe- 2-1, 2-2 ! Measurable oceanic conditions cies assemblages. Tyler 's experience with were suspected to be determinants of larval pOpulatiOn dyaamiCS Of NOrth AtlantiC survival and of juvenile growth rates. stocks facilitated the adaptation of Such mechanisms still remained to be iden- general theory to specific West Boast tified. How interspecific and intra- fisheries dynamics. Warren's work in specific competitions and other inter- general systems ecology broadened the actions within flatfish associations affect study 's approaches to problems in manage- reCruitment to fi Shable StOCkS were un- ment of multiple species. The family of knowns. A question of paramount importance subprojects which the six have subsequently to 00FW was tew great the yields from flat- headed, accordingly, represents a composite fish stocKs might be. That interest of complementary OSU and GDFWcapabilities. suggested a complex of possibilities for sampling, analyses, and computer modeling- Whether traditional approaches to stock The pr inci pal investigator s ' general management were even adequate and suf- objectives for the prospect, as defined in their first-year proposal, were. likely would have gone unaddressed for protracted periods have, instead, been 1. to def ine speci es assembl ages dealt with promptly . Each of the senior associated wi th Oover sole and researchers has been able to direct other pleuronecti ds on the commer- cial trawling grounds on Oregon's questions impinging on other fields af spe- cialization to colleagues wha were ~illing continental shelf; ta give them prOmpt attention. Throughout 2 . ta determine ecological interac- tions among associated species and the first year of the project. the prfn- cfpal investigators met monthly ta coor- factors influencing the produc- tivity of the demersal bottom- dinate their efforts. Thereafter, the team met formally at annual, internal symposia dwellfng! phase; to present their current findings and ta 3. to identify critica'l factors in plan remaining subtasks. They maintained the pelagfc water column- conmLunicatians by numerous informal meet- dwellfng! phase of pleuronectids f ngs and when they met to review graduate that may influence survival and year-class strength; and student degree programs. 4. to enable more effective fisheries Ref lectfve of the complexities of fts management through modeling and subject, multiple par tici pants, and simulation of populations, ff shery flexible administrative handling, the study effects. cast-benefits and traced out a 1 abyrinthf ne genea1 agy. multiple specfes fnteractions. Figures 2-2 through 2-5 portray interrela- Nark on 15 of the project's eventual tionships and evolution of the study's sub- 31 component subprajects began in July tasks. The time spans over which they have 1975. Figure 2-1 traces a simplified and been active can be read from the date scale at the top of each diagram. New subpro- idealized flow of efforts compr ising the jects were begun as their prerequisites project. The timing and phasing of sub- became available. Early in the second tasks have depended, in part, on the StatuS year, for example, Carey, graduate of research data that each requires. Thirteen subprojects have been done by uti- assistant Kaskan, and research assistants 1 izing pre-exi sting data. However, the Jones and Gish began a more intensive study existence of empirical information has not of flatfish prey because studies done during the first year revealed the need for meant easy access to it. Certain of the additional sampling of sediments. Simi lar- subtasks that drew on existing data exacted appreciable investment of research time to ly, Haymanand Tyler had to correlate flat- fish year-class strengths wf th ocean con- locate that information. The work directed at carrelating year-class strength of juve- ditions and to discover that there is no nile and adult flatfishes with oceanic con- relationship between stock size and re- ditions, for example, necessitated a search cruitment before they could move ahead on that led to dealing wi th six agencies simulation of sole populations. spanning the nation. Ouesti ans raised by one subproJect prompted short-term, specialized, but unan- Six subprojects requiring supplemental ticipatedd subinvestigations. Carey and sampling along with nine others that have depended entirely on original sampling Rogue undertook their study of invertebrate necessitated 69 cruises using all three of prey of coastal juvenf le flatfish to answer the university 's research vessels between questions raised by Pearcy 's work with July 1975 and November 1978. Cruises Richardson and Krygier an flatfish nur sery areas and juvenile survival rates. The varfed in duration from three hours to 16 days. for an accrued total of some 2,358 early attention given to simulating ffshery effects on flatfish production and eval- hours of ship time. Table 1 identifies uating cost-benefit ratios for management which of the subprojects required gathering data. alternatives led to an expansion and the transfer of these thrusts to a separate, Tyler has been principal investigator related Sea Grant project R/PPA-B, "NETS"! for the portions of the project devoted to headed by Courtland Smith of the OSU synthesizing computerized simulations and Department of Anthropology. That tran- managementmodels. Uecause of the study 's sition occurred in July of the third year. size and complexity, he also has doubled as Richardson's departure from Oregon State coordinator for cooperation among the University at the end of the fourth year departments and disciplines involved. He obliged curtailments and adjustments in credits the resulting collaboration with thinking on some of the hoped-for studies synergistic dividends. Ouesti ons that of the larval phase of productivity . SUBRRMECTS BASED EXISTING DATA

Na in of Distribution of Flatfishes and Assoc a oc s -Determinaltion of relationships be- distribution of flatfish tween stock size and resulting year- stocks and associated species - Tyler class strength Hayman, Tyler -Analysis of distribution of flatfish -Determinaltion of distribution and stocks and associated bottom fishes- abundance of f1atfish larvae in P earcy coastal walters - Richardson, Pearcy -Analysis of di stribution of inver- -Determinaltion of sea bottom tem- tebr ates associated with fl atfi sh perature flrom sea level data - Kruse, stocks - Carey Huyer

of Phase Between y olfe g at- fishes - Hancock, Kravitz, Pearcy populations based on catch per unit effort! of Nater Ty1 er -Simulatioh of Dover sole populations -InveStigatiOn Of di Stributian and basedon gear-class strength! Tyler duration of larval phaSeS fOr Dover, -Simulation of English sole popula- rex, and petr ale soles - Pearcy, tions - Hayden, Tyler Hosie, Richardson -Applicati on of innovations in -Correlation of year-class strength of i socline phase-plane theory to flat- flatfishes wi th oceanic conditions fish produttion systems - Liss, Warren Hayman. Tyler -Inclusion of economic factors in -5imul ation of pr ocesses af f ecting appliCatiun of iSocline phaSe-plane English sole year-class strength and theory to flatfish production systems spawning time - Kruse, Tyler - Thompson, Liss

SUBPRMECTS RE UIRING SUPPLEMENTAL DATA

bution of Flatfishes and larval English sole and other flat- fishes to oceanic condi ti ons y distibution and movement Ri ChardSOn, Laroche, Mung of juvenile vs. adult English sole- Hewi tt, Pearcy Between

of Phase y y oss from gat>on wTttn diSCarding Small flatfiSheS at sea- an assemblage of fishes on the Oregon TenEyck, lHeery shelf - Wakefield, Pearcy -Simul a ti on of f i shery ef fec ts and evaluation of cost-benefit ratios for of plater management,alternatives - Tyler -Developmi.nt of models for multi pl c- -Rel ation of year-cl ass strength of species managementstrategies - Tyler

SUBPRUJECTS RE UIRING ORIGINAL DATA coastal waters - Hogue, Carey -Analysis of vertica1 distribution ot of Phase invertebrate prey of flatfiSheS On the g t ion o ng ts ana[ Oregon shelf - Carey selectivity of Dover sole - Gabriel, -Analysis of vertical distribution Of Pearcy, Carey invertebrates in Dover so1e envi ron- -Intensive study of invertebrate com- ment - Carey, Kaskan munities preyed on by fl atfi shes on -Mapping af nursery areas for bottom- sites chosen by distribution studies- dwelling phase and study of juvenile Car ey SurVi Vat diiStri butiOnS, mOVementS, and -Measurement ot juveni le Engl i sh and growth - Pearcy, Krygier Dover sole and correlation with oceanic conditions - Kreuz, Tyler -Measurement of growth rates ot newly Phase settled juveniles - Rosenbergg, Pearcy -Determination of larval growth, sur- -Study of invertebrate prey of flat- vive!, and mortality of English sole- fishes and juvenile flatfishes in Richardson Laroche

TABLE 1. Data requirementS fOr R/OPF-1 SubprogeCtS FIGURE 2-1. Flaw af R/OPF-1 Subprajects FIGURE2-2, Chronology of subprojects investigating the disNibution of flatfish stocks and associated species

12

14

FIGURE2-4. Chronology of subprojects investigating the productivity of the water column-dwelling phase of the flatfish life cyc1e

75-76 76-77 77-78 78-79 79-80

6/81

6/8l

PHASE.4 15

FIGURE 2-5. Chronology of subprojects attempting to synthesize relationships between f1atfish productivity and fisheries

78-79

6/81 SYNTHESIZERELATIONSHIPS BETNEEI'I FLATFISH PRODUCTIVITY AND FISHERIES:::::::

ANALYZE YIELD LOSS:,::::.. 3B FROM DISCARDING SMALL: FLATF ISH AT SEA :.::.::..:,:::,:::;::::.:: :; TENEYCK 8, DEMORY!:;:-"'

7/78 ".-''S IMULATEPOPULATIONS OF DOVERSOLE .::.;,:::, 6/78 ::,' HASEQ QhJCATCH/UNI T OF.,EFF9RT DATA!:::.'-:::::,:::,::.::;. 6/81 .: .:::::.:-::: .:.-.-:::::::-.:.::::: TYLER!: ..::=-:::.:.,::::::::.:..::::.:::::-::.:::::--::::

:.:7/78

:::::SIMULATE POPULATIONS OF ENGLISH SOLE:::: 6/81 ;:,::,:'.:.:;:;:::::.:,::-;:::,::.::.;'::::.::.::: HAYDENa TYLER!:,:,:;'-::::;:::::::::::::::::::-: '-':

:,:: SIMULATE FISHERY EFFECTS AND:'-' :.:::::-:EVALUATE COST-BENEFIT RAT I OS': .:: 7/77 :.::::-::.:FOR MANAGEMENT ALTERNATIVES TRANSFERRED TO PROJECT .:.:-=.:::::::::::::::,.:.:::-:::::.,: rYt ER! R/PPA-8 NETS! C, SMITH!

:.::::::DEVELOP MODELS FOR MULTIPLE-SPECIES MANAGEMENT STRATEGIES:::-: :::.::.3/80 :,-:"'-'.:'"-':.::.:::::::.::::;:.::;:.::-::;::::.:.:..;:::.:...::.:,:::::::::.:::::::::::::::::::. T Y LES!,:;.:::,:.::.:::::.:;::.:.::;:;:.::;:;:.::;:,::::::::,::,::::,::;,:,:', ;',:;::,:....::,::;..'.:.::.:.::.::.'..::,::;:.::.::;:.:::.:.::.:::.

7 5:.: : APPLY I N NOVA T I 0 N S I N::::::::::.:.::.:.:,:::-:.::.:-':.:.::.:::.:::;:;:::-': ::::ISOCLINE PHASE-Pt ANE THEORY TO .-".. 12/77 :: FLATFISH PRODUCTION SYSTEMS.:::.::.:.::'-.:.:::::. :'::::::::::::::::.:,:;-'::: LISS R WARREN!:::.:.:.':;.:;::.:;...,:-;::;--': 1/78

::,:,::INCLUDEECONOMIC FACTORS IN APPLICATIo N OF ',:.-".':.'-:.'':'-:.:::::::;:;-, ::::'=:lSOCLINEPHASE-PLANE THEORY TO FLATFI A --- -'::;;::,:;:;::,:::::;:.::::.6/31 :.:':'-:PRODUCTION SYSTEMS ::::::::'-'::::.:.;:;:;:;:;:-:::::::::.:.:::;:.'.::,:::.::::::::::.:..,:.;.:,:;-::::.::.:::;: THOMPSONR L I SS!::;:'-:.:::::.::.-;:

..:.:8/75

,:::::::DEVELOP AND APPLY COMPUTER TECHNOLQGY;::,:.;' 6/81 :.::::'.:'-.:::.:::.:::..:::: -'-:"-::.:::,:: HEALS i WORDEN. TYLER!:::;::::.:;:,:,::,:;: -:,::,-'-:::::.':: In addi ti on to coordinating their ef forts, the princi pal investi gator s periodicallyreported their progressto the OSUSea Grant programoffice. They wrote r eports annual1y and documentedtheir planningfor remainingeffort by preparing materials for Sea Grant's proposals for renewal of funding from 1976 through198U. While the feasibility of continuing the pleuronectid study was not re-evaluated each time, progress--and changes--under the project were evaluated by the local Sea Grant administrati on, the national Sea Grant monitor, and Sea Grant site visit teams. Results to date have been docu- mented in Sea rant annual reports and in the sumnaries of accomplishments for the project in each of the renewal proposals prepared since 1975-1976. Scientific reporting on subprojectsbegan appearing in the literature in 1977 and can be expected to continue with regularity for at least the next two years. In July 1980, Sea Grant director Wick granted a 12-month extension to the original 5-year term of the project. The extension recognizes the greater than anticipated volume of data developed under the project and provides the participants continued support for analysis and documentation of findings. A sunmaryof results for the original 5-year period appearsin the following secti on.

16 The project has been an attempt to investigate aspects of the natural produc- ti vi ty of commercial ly valuabl e fl atfi sh stocks of f Oregon by treating the stocks within the ConteXt of a larger system. The investigators have examined both the struc- ture and dynamics of the multiple-species, flatfish coxmunities, what affects the pro- ductivi ty of these stocks, and how the 1 ocal trawl f i shery expl oi ts them. Thi s section suxmarizes the result of the work.

The study team subdi vi ded their researCh on pleuronectid productivity into parallel investigative efforts of reproduc- tive processes and of body growth charac- teristics. Examination of reproductive processes began with a study of the distri- bution of spawning fl atfishes. This effort aimed at expanding upon available data describing that phase of the flatfish life cycle when stocks are most vulnerable to capture by trawlers. Fisheries managers regard better understanding of this phase of productivity as one requisite for managing the stocks to perpetuate the fishery . The work on this aspect of pro- ductivity also has application in the determination of spawning times. Study efforts to determine distri bution and mor- tality of flatfish eggs and larvae have contributed to locating important spawning grounds, a second critical requisite for effective management. Findings from this subtask have improved understanding of lar- val survival rates and spawning times. Locating flatfish nur sery areas has helped round out the still incompletely understood life cycle of pleuronectids. Measurement ana analysi s of data regarding physical influences on spawning time related to the goal of determining the variables that influence the pronounced fluctuations in flatfish year-class strengths. Year-class strength is a measure of the young fish surviving after a given spawning season.!

The investigation of influences affecting hatching of eggs and survival of lar vae has the same goal. attention has also been paid to distinguishing fishery- related effects on stocks so that these can 3.1 PRUDUCTI ITY AS A FUHCTIOH OF be f ac tor ed ou t when ana 1 yzing brood REPRUDUC .IVE PROCES ES str ength yields. 3.1.1 Distribu ion of S awnin Flatfishes The purpose of i nvestigati ng body growth of newly settled juvenile flatfishes The mapping of commercial catch loca- has been to develop reliable means for tions repor ted under paragraph 3.2.1 has assessing the relative importance of the revealed an annual shift in location of portion of the flatfish life cycle spent in trawl ing ef for t for Engl i sh sole. The bay or nearshore nurseries. By comparing fleet alternates effort between nearshore growth rates of juvenile pl euronecti ds in and deeper, offshore waters on a seasonal these areas researchers are seeking to basis. To project researchers this bi- determine which environment contributes modal pattern suggested that the trawlers' more to flatfish growth. Prospect personnel target species may migrate between these have incorporated data from this subtask regions on a seasonal basis. The prospect into a computer simulation of English sole posed the question whether such movement, populations. Investigation of growth rates if consistent, might be a manifestation of in sub-adult flatfishes required sampling spawning behavior . G. Hewitt, under W . over a wide area to develop confidence in Pearcy 's supervision, examined cowercial the extent of sampling required for making fishery catch statistics from 0 to 80 reliable stock projections. An additional fathoms for the area between Coos Bay and purpose of the survey sampling has been to Cape Lookout for the years 1973, 1975, and develop understanding of seasonal variation 1976 to analyze English sole distributions in flatfish growth processes. Study of on an annual basis. His goal has been to flatfishes' food web has contibuted new determine if tahe species migrates season- understanding of feeding preferences of and ally . He has searched for any detectable availability of foodstocks to the coaIner- link between coheir seasonal movements and cially valuable f1atfishes. what is known about the life cycle of the species. Concurrently, he has assessed The second main category of research problems inherent in using conlnercial catch has focused on how the local trawl fishery records as an index of abundance for one exploits the stock off Oregon. A substan- species in a multiple-species fishery . tial share of the effort along this line has been devoted to developing computer Hewitt has found that any longshore models of productivity. One of the prelim- movement of English sole is obscured by inary tasks here has been mapping of loca- month-to-month fluctuations in fishing tions from which the comnercial catch effort caused by factors such as adverse comes, to find where the trawl fishery con- weather. Market restraints also influence centrates effort. Other preliminary tasks fishing effort,! He has found consistent have been the development of yield esti- evidence in all three years' data that mates using traditional surplus-production English sole stocks off Oregon do move and y i el d-per-recrui t methods. These have inshore and offshore seasonally . Average provided a basis for comparison of results water depth at time of capture and catch derivable wi th the modeling techniques per unit of fiShi ng effort i ncrease during developed under this project. To determine fall and early winter, suggesting a move- whether traditional management models would ment of target stocks into deeper water. allow under- or overfishing of target spe- CieS, inVeStigatOrS haVe deVelOped a Simu- Oregon's fishery for English sole 1ation of a Dover sole stock that exploits primarily females, owing to the accommodates the uncontrollable fluc- differential grOwth rateS fOr the twO tuations observed in year-class strength sexes. Hewi tt's examination of the con- and growth rate. For related reasons, dition of ovaries from English sole caught investigators have developed a conceptual near Heceta a@d Stonewa11 Banks, off the model that, argues that managementof spe- central Oregon coast, suggests that the cies that interact in a complex fishery concentrating of females in these areas and requires sustaining assemblage charac- their subsequent movement offshore do teristics as well as individual target correlate with spawning cycles. The stocks that are part of the assemblage. To average depthS Of CatCheS inCreaSe, and test an alternative managementapproach to larger and mere frequent, commercially the same hypothesis, other members of the exploitable aggregations begin appearing in project have been applying isocline theory the fall, just .prior to convnencementof to derive yie1d estimates. Influences spawning in late fall and winter. The accommodated in their methods include stocks' spring dispersal and slight inshore social and economic factors operating on movement may be components of long-shore the fishery. migrations that may alleviate intraspecific

E8 competition for food. One effect of their Both species may use the outer continental seasonal di spersal i s greatly reduced shelf and upper slope region as a nursery fishing pressure. Ref. 3-1! during the early bottom-dwelling phase of life. Petrale sole larvae were rare. 3.1.2 Di stributi on and Nor tal i of E Those that were present were taken from and Larvae March to June and appeared to spend about six months in the water column. Young-of- Richardson began work under the study the-year rex sole, uncommon in the trawl by analyzing planktonic fish larvae collections. appeared on the inner con- collected from 2 to ill km off Yaquina Bay tinental shelf only in the fall. Ref. between January 1971 and August 1972 . 3-4! Plankton from 287 bonga net tows contained 23,578 fish larvae representing 90 taxonom- Laroche and Richardson analyzed larval icc groups. Richardson identified 78 of collections from the region between the these groups to the species level. The Golumbia River and Gape Blanco primari ly data collection from which she worked also for abundance of English sole but also for includes temperature and salinity measure- butter sole. starry flounder, and sand ments at the sampling stations.! Ref. 3-2! sole! ~ Abundance. distribution and size Richardson and Pearcy have analyzed these composition of English sole larvae but not larvae as coming from two di stinct butter sole, starry flounder, and sand sale! assemblages of larval fishes: a "coastal" varied widely between late winter and early assemblage occurring 2 to 28 km offshore spring of the four years studied. In 1973 and an "offshore" assemblage at 37 to 111 English sole larvae occurred more fre- km. Richardson has recently identified a quently, were mare widely distributed, and third, "transitional " assembl age exi sting made up a greater proportion of the collec- between the coastal and offshore groups.! tionn than in any of the other three years. Three fish species, including English and Weather in the winter of 1973 was unseason- butter sole, dominate the coastal ably milder, precipitation was lower, assemblage. Slender sole is the only winds were 'lighter but more variable, and p'leuronectid found among the offshore domi- sky cover was less than in the other study nants. More than 90 percent of all larvae years. The fluctuations in larval patterns collected were netted between February and may have been related to variations in Ju'ly. Distribution patterns were similar spawning times and differences in food in both years. Adult spawning locations availabli ty . Unusual wind and weather con- and current and circulation patterns prob- ditionss may have affected the timing and ably account for the observed separation intensity of the winter phytoplankton of the assemblages. Species in the coastal bloom, leading to optimal larval feeding assemblage are similar to those found conditions and good survival that year . inside Yaquina Bay except that differing Ref. 3-5! individual species dominate in the two locations. The coastal zone is an impor- In investigating distribution and mor- tant spawning area for the English so'le, tality of English sole eggs and 1arvae, which uses Yaquina Bay estuary as a nursery Laroche, Richardson, and Rosenberg have ground during part of its early life. established and validated a technique for Ref. 3-3! determining that age of larvae and meta- morphosing p'lanktonic juveniles by counting Pearcy, Hosie, and Richardson have daily growth incr ements of otoli ths. They analyzed 593 bongo net tows and more than developed a mathematical model depicting 2,200 Isaacs-Kidd midwater trawls from the the growth af larval English sole in the study area for di stribution and larval ocean off Oregon, based on size-at-age data phases of Dover, rex, and petrale soles. for larvae caught in the field. Growth Dover sole larvae were present in all rates decreased from 0 3 mm per day at months. They appear to remain in the water eight to nine days of age to less than column for their first year of life and 0.1 mmper day between 73 to 74 days. The are most common beyond the continental latter age is about that at which English slope in the uppermost 50 m. Large larvae sole larvae in the water column transform probably remain in the water column far to bottom-dwelling juvenile fish. Knowing more than a year and exhibit low recruit- estimated age «nd rates of growth, when ment to bottom-dwelling populations. Rex combined with abundance data, enabled them sole larvae increase in size and advance in to compute mortality rates to estimate lar- development from March through February . val mortality in the ocean more accurately. Juvenile fish are common on the bottom Ref. 3-6! Richardson and others have during winter on the outer shelf. Their also traced development of butter sole from pelagic phase usually lasts about a year . egg throuqh bottom-dwelling juvenile fish by collecting at sea and by rearing speci- Pearcy and Kry gier have derived mens in the labor atory. The species is of length-frequency histograms for larva1 and potentia1 interest because it may be a main juvenile English sole in the lower Yaquina competitor with English sole in the larval phase. Ref. 3-7! Bay estuary at three stations sampled with a 1.6 m beam trawl over six years and from three stations sampled with a beach seine Richardson, Laroche, and Richar dson in 1977 and 1978. They have found recently have found the patterns of larval fish metamorphosed guveni les or 1 ate meta- distribution to be consistent throughout morphosing 1arvae from January through the winter and spring months. From addi- June. In some years recruitment of these tional work on the col 1 ecti ons they have small fish begins as ear1y as October or now di stingui shed coastal, transi tional, November and continues as late as July or and offshore assemblages that are present in each period sampled. The region of August, suggesting prolonged spawning times. transition from coastal to offshore assemblages corresponds approximately to Abundance of zero-age specimens within the break between the continental shelf and the bay has been fair1y consistent, the continental slope. Species in the coastal and offshore groups do not overlap. although in 1977 and 1978 catches were above average. The average size of juve- The consistency of these patterns may be related to the spawning location of the niles in the estuary may decrease in adults and to predominant longshore coastal autumn, apparently because the larger young-of-the-year may emigrate from the circulation patterns. They believe dif- bay. Small juvrrniles apparently occur com- ferences in offshore distribution of monly at Moolach Beach stations, often coastal assemblages may reflect differ- ences in local coastal wind patterns. appearing a month or so earlier or per- Differences in dominant taxa and their sisting a mont l or so later than in the relative abundances within assemblages may bays. The investigators' May 1978 sampling reflect variation in timing of spawning and of other estuari'es shows highest abundances surviva'I of larvae in the planktonic phase of zero-age juveniles occurring in Til- of their life cycle. Despite the differ- 1amook Bay, followed by Yaquina, Siletz, ences observed, the persistent occurrences Alsea, and Winchester Bays. Trawling along of three major assemblages and of three the open coast iin summer and fall 1978 con- major species groups supports the idea that firmed the occurr ence of juveniles on operr- these patterns of larval fish concentration coast, nearshore nursery grounds and are constant over the continental shelf reinforCes the peSsibi lity that these areas r egion off Oregon. Ref. 3-8! contribute importantly to total produc- tivity. Ref. 3-1'1! 3.1.3 Identification of Nursery Areas 3.1.4 Influences, on Spawning Times W. Laroche and Holton have discovered zero-age Eng'!i sh sole along the open coast Kruse and Tpler have tested hypotheses off Oregon. They have identified zero-age about possibl e recruitment mechanisms by specimens in samplfngs collected off developing a computer simul ation that Hoolach Beach and have analyzed the season- treats selected empirical data as indepen- ality, depth distribution, and length- dent variables. When egg production is frequency patterns of these groups. Where- correl ated wi th ei ther water temperature as the estuary has long been recognized as records and egg survival data or larval an important nur sery ground for the transport indices, their simulation model species, Laroche's and Holton's findings can account for 64 and 58 percent, respec- suggest that at least some portion of this ti vely, of the var iabi 1 i ty obser ved in year-class may spend its first year in E ngli sh sole recruitment. The par adi gm shallow, open coastal areas instead of they have used in their simulation explains exclusive1y in estuaries as previously the variation in terms of water temperature postulated Ref. 3-9!. Considering the changes and water mass transport. These vast extent of shallow, sandy bottom, factors being characteristic of the pre- unprotected nearShOre waters and relatively vailing upwellfng phenomenon leads investi- limited estuarine area along the coast, it gators to be optimistic about the model is possible that even low-density or local- serving as a uSeful estimator of stoCk ized use of these grounds may play a sig- strength. For example, it predicts nificant role in total production of increased availability of English sole in English sole within the study area. Ref. the 1980s on the basis of recent, favorable 3-10! environmental condi tions for egg and larval survival. Using the simulation, fishery

ZO managers should now be able to predict when variation for Dover sole between 1946 and to reduce future fishing effort to protect 1962 Figure 3-2!. UpweIling may have the stocks, based on measurable physical influenced food availability for newly conditions that have been shown to be unfa- feeding larval fishes, and offshore water vorable to brood survival. The model, movement may have influenced the location additionally, can distinguish when low of larval settling. For English sole ear ly recruitment fo11ows from unfavorable con- fall pre-spawning! values of upwelling, ditionss rather than from fishery pressur e. and also barometric pressure, showed sta- Ref. 3-12! tistically significant correlation with cohort strength and accounted for 84 per- In developing the simulation capabil- cent of cohort strength variability between ity, Kruse and Huyer searched the available 1955 and 1966. Fall upwelli ng delayed record of physical data for variables which warm-up of inshore bottom temperatures, related to little documented bottom water which may have delayed spawning or improved temper atures on the continental shel f of f egg condition, both of which are limited to Oregon. They have shown that sea level strOnger COhortS. correlates closely with bottom temperatures at key locations--even more so than does 3.2 PRODUCTIYITY AS A FUNCTION OF UOUY the upwe1ling index. Using regression analysis, Kruse has demonstrated that near- bottom temperatures can be assessed from 3.2.1 Growth of Early Juveniles sea level data for application in predict- ingg future stock strength. Ref. 3-13! Rosenberg and Pearcy have estimated the ages and growth rates of juvenile Kruse and Tyl er examined possibl e EngliSh sOle frOm Yaquina Bay estuary and causes of variability in the English sole from Moolach Beach nearshore nursery spawning season and found the phenomenonto grounds. Mhi'le the average growth rates be related to bottom temperature. They have been similar for the two areas, they inferred spawning times from 13 years' data appear to be more variable in juveniles on gonadal conditions of female sole, on from the estuary . Rosenberg reports an planktonic larvae, and on juveniles. They average rate of growth for specimens from have deduced three hypotheses that collec- both areas is about 10 mm in 20 days. His tively account for much of the observed calculation of individual growth rates from variability; the rate of gonadal develop- radial measurement of growth rings on oto- ment is inversely related to near-bottom liths removed from the specimens suggests water temperatures in surmner; no spawning that growth proceeds linearly, with speci- occurs at temperatures below about 7.8' C; mens from the estuary showing slightly and rapid increases in bottom water tem- faster rates in 1979 than 1978. Ref. peratures delay spawning. Ref. 3-14! 3- 16! Pearcy and Krygier have obtained Their simulation model indicates that both slightly faster growth rate estimates for stock strength and environmental factors juveniles from Yaquina Bay by an alter- contribute to recruitment strength. Using native technique employing progression of the simulation they have been able to length modesof specimens taken throughout account for 68 per cent of the variability the year by trawling in the bay . Ref. that occurred in English sole brood 3-11! strengths from 1960 through 1966 Figure 3-1!. Ref. 3-15! Rosenberg has linked findings on juve- nile growth rates with data on larval 3.1.5 Influences on E and Larval Survival growth rates measured by Laroche to derive an understanding of growth processes during Hayman and Tyler examined rela- the metamorphiC period. The species tionships betweencohort strengths of Dover appears to experience a prolonged interrup- and English soles and environmental tion to growth in length between 60 and 120 variables that might influence spawning days of age. Over' this interval the fish success or survival. Yariables that they undergo extensive morphological change but have evaluated include measuresof spawning add no length. Ref. 3-18! Apparently capacity, monthly means of oceanic and sett} ement from water column ta bottom Columbia River conditions, and measurements habitat occurs in winter and spring in the of short-term weather variability. A nearshore nursery grounds but mostly only multiple factor statistical correlation in early winter in the estuary . Ref. incorporating two oceanographic factors, 3-17! upwelli ng in early surrmrer and offshore 3.2.2 Growth of Sub-adults water movement the previous winter, explained 65 percent of the cohort strength Kreuz, Tyler, Kruse, and Demory have

21 FIGURE3-1. Comparisonbetween observed ! spawningrecords and those oredicted P! whenal1 three temperature. hyootheses are incorporated into a simulation model driven with bottom temoerature estimates. A distinction is made between spawning solid line!, peak spawning solid shaded areas! and probable peak spawnino stippled areas!. A dotted line indicates nn data.

22 Figure 3-2. Numbersof age-6 Doversole year-class strength in natural logarithms! estimated by cohort analysis solid line! compared to estimates of numbers based on environmental variables. collaborated on a study of growth rates af Dover sole off Astoria and Brookings and of The grOwing SeaSOn fOr Engl i Sh SOle Eng i sh sole off Astoria and Coos Bay . begins in Harch and extends through They measured increments of growth between September. Growth is most rapid during Hay annuli on scales and on interoperculum and June Figure 3-4!, For these months bones for Dover and English soles, respec- the correlation between fluctuations in tively. Also, the age-specific rate of growth rates for both species and variation growth for Dover sole varied significantly in near-bottom water temperatures is signi- year by year--by up to 19 percent from the ficant. Water in the area occupied by sub- average rate over the period fr om 1961 to adult English sole is cooler in summer due 1974. Dover and English sole captured off to upwelling. But the cooler water is Astoria exhibited good growth and poor associated with faster growth. 1t appears growth in the same respective years as did from work at another laboratory that cool Dover sole from waters off Brookings 460 km temperatures aey promote growth by acting south of Astoria and English sole captured directly on physiological processes off Coos Bay 300 km to the south of 9overning growth Ref. 2-2 ! ~ Al so, the Astoria. Dover sole taken off Astoria grew cooler upwelled water is richer in significantly faster than samples of the nutrients and promotes productivity of same species captured off Brookings. algae and hence food animals of the sub- English sole from off Astoria and Coos Bay adult soles- Both annual fluctuations and exhibited no such differential growth. long-term trends in upwelling and bottom Growth rates for Dover sole fr om off temperature show strong relationship to Astoria showed a general long-term increase growth rates of English and Dover sole. between 1958 and 1966' followed by a grad- Growth does not appear to be associated ual decrease through 1969 Figure 3-3!. wi th stock deasitI of either Dover or Their average rate then fluctuated widely English sole far the time period that was through the mid-1970s. Data for English tested. Kef. 3-19! sole exhibit a similar long-term trend that 3.2.3 Food Web and Food-kner Pathw s in is less apparent because the information the Natural Pro uction System base does not cover a correspondingly lang period. Ref. 3-19! Ty 1 er ha s contr i bu ted to basel inc

23

FIGURE3-4. Changesin seasonalgrowth incrementfor Englfsh sole with bottomtemperature f indings for the pleuronectid project disturbance of habitat apparently reduce through study of the stomach emptying rates food resour ces parti tionf ng. Regularly of Atlantic cod. He found that juvenile repeated disturbances, such as intermittent ffsh obliged to swim at controlled speeds ocean pollution, may favor the increase of after consuming measured quantities of food populations of prolific, shorter lived spe- showed no relationship between swimming cies, may reduce food partitioning, and may speed and rate of emptyfng their stomachs, support predator populations that otherwise except at the highest swimming speed. His would not occur. Ref. 3-22 ! work suggests that gastric emptying rate is fndependent of swfmmingactivity at normal Carey, Hogue, and Kaskan have investi- swimming rates. Thfs finding facilitates gated the availability of prey to predators estimating daily rations of fish fn nature. and food sources for juvenile English sole. Ref. 3-ZOJ He subsequently has done work They samp!ed bottom-dwellfng organi sms at to determine if diet choice changes six stations transecting selected fishing abruptly about some threshold size of prey grounds to measure the physical availabil- for a determinate size of predator. He fty of prey to pleuronectids. Sectfonfng succeeded in devel:oping a technique for of box core samples from these stations has classifying predators into size strata y ielded data on the composf ti oe, abun- correspondfng to sizes of prey taken. dances, and vertfcal dkstrf'bution of prey There apparently exf sts a threshol d size species fnhabftihg bottom sediments. Nost relatfonshf p between predator and prey. species of invertebrate prey inhabf t the Ref. 3-21! Ty1er al so has found food upper few centimeters of sediments; only a resource partitioning to be influenced by a few forms exist deeper in the layers combination of predator-prey effects and sampTed at most statf ons. Juvenile sand disturbance of habitat by physical influ- sole, Engl f sh sol e, butter sole, and ences. The larger the degree of distur- speckled sanddab use the nursery ground off bance. the weaker the degree of food Nioolach Beach. The amounts and types of par ti tf oning obser ved, The combined prey available to them are important deter- effects of natura1 perturbation and human minants of their growth rates and. perhaps, year-class success. The investigators depthS to 195 ai in clayey Silt and Si'lty examined gut contents of zero-age juvenile sand sediments. The food habits of Dover flatfish from the nearshore area to iden- sole show similarities at stations of simi- tify which bottom-Arelling species they lar depth but Irot among stations at dif- take; to monitor seasonal changes in fering depths but similar sediments. Dover feeding habits; to determine distribution sole taken in winter had the higheSt per- of prey species in time and space; and to centage of empty stomachs, suggesting that relate gut contents to types of bottom this species may feed more intensively in sediment. They have found that the four surmrrer. Small rex sole were found to feed species studied repr esent a trophic con- mainly on amphipodsand other crustaceans. tinuum. Juvenile English sole feed exclu- Large rex sole fed chiefly on polychaetes. sively on the bottom, butter sole feed on This species is less diverse in its feeding bottom-dwelling inver tebrates and prey in preferences than Dover sol e and over 1 aps the water column, speckled sanddab little in its selection of prey with that generally take prey from the water column of Dover sole. Pacific sanddab, the most but sometimes feed on organisms in bottom numerous corrmon species at shallow sand sediment, while sand sole feed exclusively sites, and slender sole, the most cormron in the water column. The feeding behavior species at three deep, soft sediment sta- of juvenile English sole changes seasonally tions, prey principally on open-ocean as a result of changes in the availability crustaceans such as euphausids, shrimps, of prey . Ref. 3-23! and amphipods. Pacific sanddab feed mainly on open-ocean crustaceans and fishes. From earlier Sea Grant-supported Ref. 3-26! research Bertrand and Carey report four distinct corrmrunities of inver tebrate prey Kravi tz, Pear cy, and Guin have organisms in the sediments of the central described food selectivity for co-occurring shelf. They correspond to four distinct English sole, rex sole, rock sole, petrale types of sediment that more or less sole, and Pacific sanddab. English sole parallel the coastline. The four zones are takeS a diverSe diet of polychaetes and distinct substrates of beach sand, mixed amphipods that also includes mollusks, silt and sand, silt, and glauconitic sand. ophiuroids, crustaceans, and pelecypods. The animal species occupying these habitats Rock sole take principally ophiuroids plus are low in diversity, abundance, and some polychae>s and rrellusks, and biomass despite the high pr oductivi ty of ocassionally shrimps, other crustaceans, the overlying waters. No significant herring, SandlanCe, eChinOdermS, and mrrphi- change in composition or numbers is evident pads ~ Petrale sole prey on fishes and thr ough the seasons at arly station from 75 decapod crustaceans but not on polychaetes to 450 m. Sediment characteristics such as and amphipods. Other researchers have content of organic carbon, organic nitro- reported finding euphausiids, herring, gen, and sediment particle size similarly sandlance, shrimp, and open-ocean fishes show no significant seasonal change. The among their stomach contents. The indica- differences occurring in biomass and abun- tions suggest that the species feeds dance of individuals in the four zones, in large'ly on open-ocean prey. Ref. 3-27! comparison to those in other areas on the continental she'lf, probably reflect the Nakefield arrd Pearcy have investigated effects of submarine topography and con- feeding among an assemblage of bottom sequent current patterns and distributions fishes on the inner continental shelf off of sediments. Ref. 3-24, 3-25! Newport.. They studied food partitioning amOng fiSheS, pOSSible predatiOn On juve- Pearcy and Hancock have studied feeding nile English solve, and species composition habits of Dover, rex, and slender soles and and size range of fishes in shallow and Pacific sanddab at seven stations on the deep waters. Trawling off Noolach Beach continental shelf. They have determined has revealed diiIferences in assemblagesat that Dover sole feed on a large variety of shallow and at intermediate depths. invertebrate SpeCieS dwelling in and about Species showing up in deeper tows, in the bottom sediments. Diets vary with decreasing order of abundance, were Pacific depth and type of sediment. Pelecypods are sanddab, English sole, butter sole, Dover the most important prey at shallow depth sole, petrale sole, rex sole, and rock 4 m! in well-sorted sandy bottom com- sole. The tows at shallow and intermediate munities. To depths of about 100 m ophiur- depths were dominated by sand sole, butter oids, sea pens, sea anemones.and pelecy- sole, and starry flOunder. 1n shallow pods are the main prey in silty sand and water big skate, ratfish, and Pacific sandy silt corrnunities. Polychaetes make tolcod were abundant. Ref. 3-28! up more than 90 percent of the diet at

26 Gabriel has examined feeding selec- to that of juvenffe English sole. tivity of Dover sole from two areas of the Productfon at offshore feeding and central contrnental shelf. She has iden- spawning grounds. is based on detritus and tified 35 principal prey taxa from speci- phytoplankton. Subadult and adult English mens taken at 119 m and 25 taxa from fish sole there feed on a broad spectrum of netted at 426 m. At both depths poly- organisms occurring in and on the bottom, chaetes and ophfuroids are more important aS deSCribed abOVe. An aSSemblage Of prey than mOlluSkS and cruStaCeanS. fishes and invevtebrate carnivores may com- Stanach contents indicate that larger fish pete for food with English sole. These are increasingly selective i n their feeding pathways represent overlapping food con- preferences. The body size of prey . as suming groups that terminate with car- reported by Tyler, increases wi th predator nivOreS at highe' trOphiC levelS. Slim size. Success in capturing prey appear s to sculpin, blackbe'lly eelpout, Pacific tom- vary wi th the size of the predator. It may cod, and ratfislh display food habi ts that be energetically advantageous for larger are more like those of English sole than fish to extract a few large bottom-dwelling are any other roundfishes . Some predatory organisms from below two cm in the sediment invertebrates also divert energy from than to hunt many small, surface prey . It English sole production . is also possible that small flatfishes may be physically unable to extract prey fr om English so$e, in turn, are prey to deep within the sediment. Ref. 3-29, a number of carnivores at different stages 3-30, 3-31! of their life Cycle. Recent studies of food habits of Juvenile salmonids and wolf- Makefield has described the food web eels show that larval and metamorphosing centering on English sole fn an attempt to flatfishes are a princi pal prey of these sujtwarf ze potential f ceding inter acti ons species. Ref. 3-32 . 3-33! Invertebrate within this flatfish assemblage Figure predation may ble an even more significant 3-5!, He has synthesized information from source of mortality for sett/ing English original obser vati ons wi th publ i shed and sole. Abundant crangonid shrimp prey unpub'fished reports of the distribution and heavily on juveni'le flatfi shes in all nurs- food habits of Pacific Northwest coastal ery areas. Li ngcod and big skate feed on fishes, marine mamaals, and sea birds. juvenile flatfishes in shallow, open coast Figure 3-5 depicts the main li~ks direct'ly areas. In deeper water s, subadult and involving English sole as solid lines and adult English sole are prey of lingcod, potential overlaps between this species and longnose skate. and petrale sole. associated fishes and invertebrates as UndOubtedly other fishes are alSO pleurO- daShed lfnes. The diagram dfStinguiShes nectid predators. Finally, English sole relationships in open-ocean and estuarine are a princfpal component of harbor seals' nursery areas from those on somewhatdeeper diet in the estuary and on the continental water feeding grounds for subadult and shelf. Ref. 3-34! adult fishes. Nursery areas and feedi ng grounds constitute separ ate subsystems. 3.3 USE OF NATU AL PRODUCTIVITY BY DOMESTIC Energy flows through three trophic levels ~IHEF RY, at each and may or may not end with English sole. The figure represents the complexi- 3.3.1 Na in and Characterizin Coaiaercial ties of thfs relationship. Catches

Production in open coast and estuarine Tyler and others have developed a com- nursery areas is based on phytoplankton, puter graphics capability for digesting bottom algae, and land and aquatic detri- trawlers' logbook data and portraying them tus. Newly settled and older juvenile as "three-dimensiOnal" plots of catch con- flatfish feed on inter mediate size sedimen- centration or fishery effort. The resul t- tary species, including copepods, larger ing graphics can facilitate interpretation species such as amphipods, polychaetes, and and application of the statfstics by cmaaceans, as well as regenerated parts resource managers. Figures 3-6 and 3-7 such as polychaete tentacles and mollusk i 1lustrate the capability of this routine siphons. Polychaetes. crangonid shrimp, to translate quantitative information to and other invertebrates prey on principal easy-to-interpret visuals. Ref. 3-35j prey of English sole. It appears that major food resources of juvenile English OOFYcollected data from trawlers' logs sole are also coawmn in the diet of similar from the AStOrfa fleet during 1975. Using size butter sole. Other juvenf le fishes computer procesaing, Tyler has coded and generally feed off the bottom but sometimes analyzed the daga for seasonal patterns of return to the bottom to take prey similar fishfng effort and for catch compositions

27 ~ v! m z g m D C z

hmh m~m Omg cag CII

A I m 8* D 3 ~$ <3 e or cn$ hg 0 Z D9 d'or+~ w cN h3 C r cn cn go CIIrII h f LI 1 C Ig C Ij~ r 92 I~ 0 D v! z pl 92 c g I ~oz j I m coo I I 92 I c 3& DD ~C Z z3 c~O r cn I D Zl 0= oo my vl III ~ 5 cir mme corn I

RK3 OI Dm 3h OSrq D O ~~o %he zxz 3 w rn o ghm mgz ~goz hZ D oo~ z o z h ggo

FIGURE3-S. Portion of food web off Oregon and Washington showing direction of food-energy flow for Eng»sh s»e and associates Dashedlines shnw ootential ly comnetitive transfer away from English sole 28 4FIGURE 3-6.Computer mapsof Oregon catches FIGURE 3-7. Computer maps of Oregon catches for English so>e for Qover sole

29 for eight groundfish species. including six var i abl es that influence natural produc- pl euronectids. He has defined and tivi ty. Tyler and others believe that described eight catch compositi on claSSes adjusting al 1owabl e fishing ef for t and or recurrent species mixes. The analysis landing quotas yearly can lead more real- has identified the propor ti on of monthly i sti cal ly to maintaining desired stock effort directed to each recurrent species 1 evel s. actually, some governmental man- mix. And it has led to a separate investi- agement agencies, e.g., Northeast Fisher- gation under contract with Courtland Smith. ies Center, NMFS, and Canadian Fisheries Ref. 3-36! and Oceans Assessment roup, Halifax! have been setting different quotas annually . In 3.3.2 Yield Estimates from Tradi tional developing their simulation model for Model s northern Uregon Dover sole, Ty1er and his associates have found that an appreciable Hayman, Ty1er, and Demory have calcu- annual adjustment to landings quota is lated indices of year-class strength, stock required to reach maximum yields without size. and sustainable fisheries yield for overfishing Figure 3-8!. Variability in female Dover and English sole by catch-per- recruitment productivity necessitates such uni t-effort CPUE! and cohor t analy si s adjustment. They believe that catch and methods. Effort data for Dover sole were effort quotas developed from average shown to be unreliable for indexing CPUE dynamic bases Could lead to underfishing abundance. Cohort analysis estimates show or overfishingI within a single five-year a gradual decline in female stock size in period in the iaInedlate future. Tyler 's the 1950s. a 1eveling off at lower abun- computerized stock assessment model for the dance in the 1960s. and an increase in the northern Oregon, Dover sole stock accepts 1970s. These trends in stock size appear data on actual variations in year-class to lag parallel trends in recruitment. strength and grqwth rate and predicts lower Estimates of yield from parabolic surplus yield levels tpan do traditional methods production models indicate that only based on empiriqal modelling. Ref. 3-39.! slightly higher yields may be achievable by increasing fishing effort. 3.3.4 liana in Fisheries to Maintain Assembla e Un t nstead of 0 timum Yields For English sole CPUE was sho~n to be a useful index of abundance of fish. Female Ty1 er and fel low investi gator s have stock size increased when the 1961 year- cone to believe that fishery management class was recruited but has since declined. objecti ves must embrace not only tradi- tional goals fqr target species but also Inadequacies in the effort data for goals of maintaining fish assemblage units. Dover sol e seem to correspond to fluc- They and others suggest that the paramount tuating market demand and technique used to concern for managing a renewable resource assign effort to discrete species in a has to be preServation of managment multip1e species fishery . The investiga- options. Fishery management aimed at tors believe that cohort analysis, there- attaining maximm sustainable yield will fore, is a better determinant of year-class likely result in simplification of the pro- strength than CPUE analysis. For English duction system and domination by species sole, nonetheless. CPUE analysis apparently exhibiting highest reproductive rates. iS as reliable aS COhOrt analySiS. Ref. They maintain that there is no empirical 3-37, 3-3e! basis for assuming that simplified. high productivity in portions of formerly 3.3.3 Yield Estimates from Simulation diverse fish assemblages can persist in the Showin Trade-Off Between Constant Landin ocean environnmnt. They also suggest that and Maximum Landin s managing one species for optimum yield risks perturbing the assemblage such thai On a national basis tr adi tional manage- it will not return to its original species ment methods have attempted to target the compOSitiOn when fiShing effort iS reduCed. same catch quotas every year by manipulat- Effort under the pleuronectid project ing or otherwise accommodating biological, indicates that geographic assemblagesof economic, and social factors affecting fish fishes exist off Uregon. Figures 3-9 and prOduCtiOn. ThiS apprOaCh CallS fOr 3-10.! The make-ups of most assemblages balanCing rateS Of fiShery-induCed mqrtal- are consistent with the depths at which ity and natural mortality against biolog- they exist. Tihere may be four to six ical productivity at a determinabl'e level. assemblages acrosS the range ot 20 to 400 The methods used traditionally, however, meters' depth. Ref. 3-40! Project inem- do not take into account uncontrollab1e bers propose that each assemblage may be

30

UMBIA RIVER

46 OOK HEAD

MEA RES

10 km HEAD 450

I NEATHER

I I 125' l24

FlGURE3-9, Fish assemblage maps for the continental shelf off Oregon

32 ASSEMBLAGE10155

0 80

ASSEMBLAGE6 105

0 80

ASSEMBLAGE

IO

z O

25 o ASSEMBLAGE 10 15 IO5

0 20

15 ASSEMBLAGE10

5

FIGURE3-10. Assemblagecomposition along a transect east to west from points between Cape Neares and Cascade Head

33 part of a geographically definable natural region set hsfde for a demonstration productionsystem of fnteractfn~organfsms fi shi ng. Ref. 3-38, 3-42 ! that they label a "caalnunf ty. Species found fn the same area that do not interact Pearcy has described species asso- with the organisms of the community are not ciations, biomass and sizes of tfshes. and par t of that functi anal assemblage. their relationship to sediments, depth, and Species occurring year-round within the season off the central Oregon coast. Ref. community comprise its "assemblage produc- 3-43! Gabriel and Tyler have described tfon unit." The assemblage production units bottom-dwelling fish assemblages on the are analagous ta fishery stocks for single- Oregon continental shelf between the mouth species ffshery managementconcerns. Ref. of the Columbia River and Yaquina Head, 3-41! based on data regarding species biomass ca1lected during a 1977 survey of rackffsh. Apparently the coriunity and its com- They compared these assemblages with those ponent assemblage production unit APU! are described fram data collected in 1973 by influenced by physical and chemical factors DDFN otter trawl survey. The species domi- that are often driven by forces such as nating each are consistent for the twa with upwelling which is a result of atmaspheric but one exception. Assemblages occur off dynamics!. They are also subject to biotic Oregon in four major zones: the neritic, drfvi ng factors. The production processes from nearshore ta 90 m; intermediate shelf of species that are regular components of zone, 90 to 145 m; the deep shelf zone, 145 the assemblage production unit likely are ta 220 m; and the slope, beginning at 220 driven by effects of species moving season- m. Over these four zones they have iden- ally or occasionally through the area. tifiedd 12 assemblages: The Columbia Accordingly, the investigators treat the Shallows, Falcon Shallows, Nestucca seasonal species as driving factors. To Shallows, Columbia Intermediate, Tillamook model them as specfes would require Intermediate, Nestucca Intermediate, modeling regions and processes outside the Tillamook Deep, Falcon Shale, Nestucca area occupied by the assemblage productian Deep, Tfllamook Slope, Cascade Slope, and unit. Columbia Slope. Many of the species in these assemblages undertake seasonal move- Rather than basing assemblage- ments or migrations, so Gabrfel's and productfon-unit management strategy on Tyler 's descriptfon of them relates pri- equilibrium or the average state, the APU marily to their condition in suaeer. The model represents a transition state. In shallow water assemblages are characterized fact. the transition state may be the only mainly by dilfferences fn pleuronectids r ea1 f ty for many systems of speci es. present and in abundances. The inter- Per turb ati on of a sy stem by internal . mediate shelf assemblages are daminated by density-dependent factors or by inter Pacific whiting or hake! in the suevnerand specific 'limit cycles may induce wide, by species whose distributions overlap fram cyclic fluctuations. A growing literatur e the shallow shelf and deep shelf zones. suggests that oceanfc trends often dominate The deep shel,f assemblages are charac- fish productivity . Under such influences terized by combfnatfons of rockfish an equilfbr ium yield would never even be species. Paaific ocean perch, Pacific approached. whfting, arrowtooth flounder, Dover sa1e, sableffsh, and darkblotched rockfish tend Monitoring the transition states to be more abundant throughout the deep following cantrolled, pulsed fishing by the shelf and slope zone assemblages. The trawl fleet may offer a means of exploring slope assemblages are set apart chiefly by and maintaining the viability of assemblage combfnations of rackfish species. Ref. production units. Instead of watching a 3-40! range of APU yields and component escape- ments during periods of constant fishing Tyler, Gabriel, and Overholtz have com- effort, the fishery manager could monitor mented on the difficulties of managing the recovery of assemblage structure ocean fisheries on a species-by-species fallowing fishing pulses of various magni- basis where the fishing method takes mixes tudes. The pulses could be applied of species. Data requirements for applying simultaneously to a group of APUs. A management models based on yield models are research goal would be ta find out if all prohibitive. Problems exist because of species of the APU recover despite the interactions among species. Ref. 3-41! magnitude of the pulse. Thus, the goa1 would be to find the limits of repetitive 3.3.5 A licatfon of Isocline Theor ta pulsed fishing that allow the APU to per- Fisher Yield St mates sist. Project investigators suggest that this type of managementbe carried out in a Li ss, Thompson, and Marren have

34 expl or ed assemblage maintenance prospects nectids exploit not individual species by adaptation of game management isocline populations bug entire marine fish com- theory. This subtask constftutes a long- munitiess. Thenefore, to obtain a desired term investment aiming at eventual develop- yield, the resource manager needs to bring ment of more adequate management cap- the entire corrmrpnftg to the stage where it abilities. Isocline theory involves a can support the desired level of exploi ta- graphic calculus that can be used to derive tion. EffeCtfve management of such specieS generalizations about interacting fish groups requires consideration of demand for populations. The researchers adapted tech- the catch, costs of fishing, and other fac- niques free game management applications. tors which infl!uence the community struc- As applied to game management, fsocline ture. Ref. 3-44 through 3-47! theory cormronly has not accommodated in- fluences of environmental, variables. The study group has refined the method, relating the theory to factors that affect the dynamics of a fish corrmrunfty. They have examined the effects of changing environmental conditions, of changing com- position of a fish assemblage, and how a hypothetical fishery responds to such fluc- tuations. Among the variable factors evaluated were: energy entering the pro- duction system. demand for' the fish in the economy, and the characteristic costs that differing levels of effOrt incur. They have analyzed components of the llypothet- ical fishery to investigate how each may affect the multiple-species assemblageon which it is based. By varying aspects of trophic structure the investigators have been able to test the effects of the lower feeding levels on productivity of the assemblage.

Accorrmrodating a sport fishery 's effects has enab'ledthem to model how the exploited stock 's 'loss rate increases under this per- turbation, how such activity competes with trawling effort, and how non-monetary bene- fits influence fishery management. In- cluding a competing exploited population in their analyses has enabled them to show that taking of the second species contri- butes indirectly to the first's gain or loss rate by altering the loss rate in the assemblage's herbivore population as well as the rate of gai n fn fishing effort!.

Isocline theory ShOwSthat fiShery com- munitiess such as the assemblage production units proposed by Tyler and others exhibit a potential for multiple stea@ states of productivity. In effect, there may be an unlimited number of practicable carrying capacities for a population, depending on how that population fnteracts with its cormrrunfty and influences affecting the com- munity. Lfss, Thompson, and Warren have suggested that isocline analysis implies that multiple-Species ffsheries may be more prone to being overfi shed than si ngle- species fisheries. In essence, ffsheries such as Oregon's trawl fishery for pleuro-

APPEN I

2-1. Ketchen, K.S. 1956. Factor s influencing the survival of the lemon sole Paro hr s ve ulus! in Hecate Strait, Br s olum . J. Fish. Res. &d. Can. 13: 647-694.

2-2 . Alderdice. D.F., and C.R, Forrester. 1965. Some effects of temperature and salinity on early development and survival of the English sole Paro hr s vetulusj. J. Fish. Res. Bd. Can. : - l. 3-1. Hewitt, G.R. 1980' Seasonal changes in Engli sh sol g distribution: An analysis of the inshore trawl fi shery of f Oregon. M.S. thesis. Oregon State University.

3-2. Richardson, S.L. 1977. Larval fishes in ocean eater! off Yaquina Bay, Oregon: Abundance, di stlribution, and seasonali ty, January 1971 te August 1972. Sea Grant publication ORESU-T-77-003,Oregon State University .

3-3. Richardson, S.L., and W.G. Pearcy. 1977. Coastal 'and oceanic fish larvae in an area of upwelling off Yaquina Bay, Oregon. Fish. 8ull., U.S. 75:125-145.

3-4. Pearcy, W-Gee M.J. Hosfe, and S.L. Richardson' 19Ip7. Distribution and dura- tion of pelagic life of larvae of Dover 1 Mi to ificus; rex sole. an petrale sole, J i, waters of f Oregon. s ~~ ~ ~ u l.,~ ~ ~75:173-183.

3-5. Laroche. J.Le e and S.L. Richardson. 1979. Winter-s+ing abundance of larval English sole, aro hr s vetulus. between the CotombiaRi er ann apeeeanco, breton during 1972-1975 with notes on occurrences of three other pleuronectids. Estuarine and Coastal Mar. Sci. 8.455-476.

3-6. Laroche, J. Lee S.L. Richardson, and A.A. Rosenberg. ln press. Age and growth

37 of a pleuronectid, Paro hr s vetulus, grounds. Sea Grant annual report 1979-1980 during the pelagic larva per o ihnlregon for project R/OPF-1. Oregon State coastal waters. Fish. Bull., U.S. University.

3.7. Richardson ~ S.I. ~, J.R. Dunn, and N.A. 3-18 . Rosenberg, A.Awu and J .L. Laroche. Naplin. 1980. Eggs and larvae of butter In press. Growth during metamorphosis of so'le, Iso setta f sole is pl euronectidae!, English sole, Par o hr s vetulus. Accepted. off Oregon an as sng on. Fish. Bull., Fish. Bull., U. U.S. 78:401-417.

3-8. Ri char dson, S.L., J.L. Laroche, and 3-l9. Kreuz, K.Fag A.V. Tyler, G.H. Kruse, and R.L. Demory. 1981. Variation in growth M.O. Richardson. l980. Larval fish assemblages and associations in the of Dover sole and English sole as related northeast Pacific Ocean along the Oregon to upwelling. Environmental Biology of coast, winter-spring 1972-1975. Estuarine Fishes. Trans. Am. Fish. Soc . In press. and Coastal Mar . Sci. 11:671-699. 3-20. Tyler, A.V. 1977. Evidence for the 3-9. Westerheim, S.J . 1955. Size com- assumption of independence between gastric position. growth, and seasonal abundance of emptying rate and swimming activity using juvenile English sole in Yaquina Bay. Atlantic cod, Gadus morhua. J. Fish. Res ~ Fish. Coasn.Oregon Res. Briefs 6:4-9. Board Canada 34:YET-2473.

3-10. Laroche, M.Aen and R.L. Holton. 3-21. Tyler. A.V. 1979. Statistical analy- 1979. Occurrence of 0-age English sole, sis of diet differences related to body ~parahr s vetulus. along the Oregoncoast: size. In: C.A. Simestad and S.J. Lipovsky an open co~as nursery area? Northwest Sci. eds. !. Wish Food Habit Studies. Proc. 2d 53 !:94-96. Pacific Technical Workshop. U~ Wash. Sea Grant, Seattle, 51-55. 3-11. Pearcy ~ WuG., and E.E . Krygier. 1980. Ecology of 0-age group Eng'lish sole. 3-22. Ty 1 er, A.V. 1979. Appar ent Sea Grant annual report 1979-1980 for pro- influence of fluctuations in physical fac- ject R/OPF-l. Oregon State University. tors on food resource partitioning, a spec- ul ati ve review In: C.A. Simestad and 3-12. Kruse, G.H. 1980. A simul ation S.J. Li povsky, eg!s. ! . Fish Food Habit model of English sole Paro hr s vetulus! Studies. Proc. 2d Pacific Technical recruitment mechanisms. .. essa~agon Workshop. U. NaSh. Sea Grant, Seattl e, 164-169. State University.

3-13. Kruse, G.Hug and A. Huyer. 1980. 3-23. Carey, Jreg A.Gee E.W. Hogue, and L. Kaskan. Intensive study of invertebrate The relationship between shelf tem- prey of pl euronec ti ds: avail abi 1 i ty and peratures, coastal sea level and the coastal upwelling index off Newport, meiobenthic-juvenile English sole food web. Sea Grant annua'I report '1979-1980 for pro- Oregon. Limnology and Oceanography . In ject R/OPF-l. Oregon State University. press. 3%4. Bertrand, G.Ane and A.G. Carey, Jr. 3-14. Kruse, G.Hf e and A.V. Tyler. 1980. Influence of physical factors on English 1980. Infaunal cemunities of the central so1e ~Parehr s vetulus! spawning season. Oregon continental shelf. Unpublished. Oregon State University . Oregon State University. 3-25. Bertrand, G.A., and A.G. Carey, Jr. 3-15. Kruse, G.H., and A.V. Tyler. 1980. 1980. A comparative study of the infaunal Recruitment simulation of English sole. biomass and numbers of the central Oregon Sea Grant annual report 1979-1980 for pro- continental shelf. Unpublished. Oregon ject R/OPF-1. Oregon State University . State University .

3-1 6. Rosenber g, A.A. 1981. Growth of 3-26. Pearcy, N.Gng and D. Hancock. 1978. juvenile English so1e, Paro hr s vetulus, Feeding habits of Dover sole, Nicrostomus in estuarine and open coas a nursery acificus; ren sole, G1 torte e us grounds. H.S. thes i s. Oregon State zac srus; slender sole, o se a ex» s; University. aand aaci fit sdnddah; Cvt orient s sor- didus. in a region of diverse se ments and 3-17. Rosenberg, A.Aag and W.G. Pearcy . ~at ymetry off Oregon. Fi sh. Bul 1 .. U.S. The growth of English sole from two nursery 75:641-651. 3-27. Kravitz, M.Jee N.4. Pearcy, and M.P. Lackey and L.A. Nielsen eds.!. Fisheries Guin. 1977. Food of five species of cooc- Management. Blackwell pp. 111-147. curring flatfishes on Oregon's continental shelf. Fish Bull., U.S. 74:984. 3-39. Tyler. ADV. 1979 ' Environmenta'I influences of fishery sustai nabi lity . Sea Grant annual report 1978-1979 for project 3-28. Wakefield, W.W., and N.G. Pearcy . R/OPF-l. Oregon State University . 1980. Feeding relationships within an assemblage of demersal and nektobenthic 3-40. Gabr i el, W.L., and A.V. Ty I er . fishes on the Oregon shelf. Sea Grant 1980. Preliminary analysis of Pacific coast annual report 1979-1980 for project demer sal fi sh assembl ages. Mar . Fi sh. R/OPF-l. Oregon State University. Review liar.-Apr. 83-88.

3 29. Gabriel, W Le e and W G. Pearcy. 3-41. Tyler, A Y., M.L. abriel, and W.J. 1981. Feeding selectivity of the Dover sole Overholtz. 1981. An alternative assemblage Microstomus aci ficus Lockington! of f management approach in a mixed groundfish Orregon. s i. u .... in press. fishery. Can J. Fish. Aquat. Sci. In press.

3-30. Gabriel, W.L. 1979. Stati sties of 3-42. Tyler, A.Y. 1980. A'I ternati ve selectivity. In: C.A. Simenstadd and S.J. as sembl age management approaches. Sea Lipovsky edseTe Fish Food Habit Studies. Grant annual report 1979-1980 for project Proc 2d Pacific Technical Morkshop. U. R/OPF-l. Oregon State University. Wash. Sea Grant, Seattle, 62-66. 3-43. Pearcy, W.G. 1978. Distribution and 3-31. Gabriel, W.L. 1979. Feeding selec- abundance of sma1 1 fl atfi shes and other tivity of Dover sole off Oregon. In: C.A. demersal fishes in a r egi on of di verse Simenstad and S.J. Lipovsky eds ~ Fish sediments and bathymetry of f Oregon. Fi sh. Food Habit Studies. Proc. 2d Pacific Bul I -, U.S. 75:629-640. Technical Workshop. U. 'Nash. Sea Grant. Seattle, 129-130. 3-44. Liss, W.J. 1977. Toward a general theory of exploitation of fish populations. 3-32. Peterson, W.Tee R.D. Brodeur, and W. Ph.D. thesis. Oregon State University . G. Pearcy. Unpublished. Feeding habits of juvenile salmonids in the Oregon coastal 3-45. Liss, 'N,J., G.C. Thompson, and C.E. zone in June 1979. Warren. 1980. Interpretative appl-ication to the benthic fisher ies of a genera! 3-33 W.W. Wakefie Id . 1 980. Unpublished. theOry Of produCtivity and resource utili- Occurrence and food habi ts of pelagic zation. Sea Grant annual report 1979-1980 Anarrhichthys peel latus juveniles collected for project R/OPF-l. Oregon State Uni ver si ty.

3-46. 'Warrens C.Eeu and W.J. Liss. 1980. 3-34. Wakefield, N. 1980. Oregon shelf Adaptation to aquatic environments. In: food web focusing on English sole. R.T. Lackey and L.A. Nielsen, edse7u Unpublished. Oregon State University . FisherieS Management. John Wiley and Sons, New York. pp. 1$-40. 3-35. Tyler, A.V. 1977. Sea Grant annual repor t 1976-1977 for project R/OPF-1. 3-47. Liss, M.,Juu and C.E. Warren. 1980. Oregon State University . Ecology of aquatic systems. In: R.T. Lackey and L.A. Nielsen, edseje Fisheries 3-36. Tyl er. A.V. 1980. Mul ti-speci es Management. John Ni ley and Sons, New York. fishery analysis. Sea Grant annual report pp. 41-80. 1979-1980 for project R/OPF-l. Oregon State University .

3-37. Hayman, R.Aee A.V. Tyler, and R.L. Demory. A comparison between cohort analy- sis and catch per unit effort for Dover sole Microstamus aci ficus! and English sole ~aro r s uetu us . rane. Am. Fish. Soc. 1

3-38. Ty1er, A.V., and Y.F. Gal luce i 1980. Dynamics of fished stocks. In: R.T.

39 kelated Publications Not Cited and along the coast of Oregon; the impor- tance of estuarine nursery gr ounds. Ber trand, G.A., and A.G. Car ey, Jr. In preparation. An analysis of infauna of the kichardson, S.L. Pelagic eggs and larvae central Oregon continental shel f. of the deepSea SOle, Fmbassichth s ~bath- bi uS lIPiSCeS: PleurOneCtidae , with Carey, A.G., Jr. In preparation. Macro- co mr!ents on generic affinities. Fish. infaunal and mega-epifaunal species groups Bull., U.S. 79!. In press. on the central Dregon continental shelf. Richardson, S. L., and J .L. Laroche. In Carey, A.G., Jr. and H.R. Jones. In pre- preparati On. Early life hiStOry patte rnS parationn. The ver tical distribution of of English sole. ~Parshr s vetulus central Oregon continental shel f infauna Pleuronecti daej: di str>button, transport, within the sediment. natural mortality.

Gabriel, W.L., 1978. Feeding habits and kichardson, S.Lo o and u. StephenSOn. 1978. feeding selectivity of the Dover sole Larval fish data: a new apprOaCh tO analy- Microstomus acificus!. M.S. thesis. si s. Sea Grant publ. ORESU-T-7B-UO2. O~regon tate Un versvty. Oregon State University.

Hayden. T.koo and A.V. Tyler. In prepara- TenEyck, N., and R.L. Uemory. 1915. tion. A computer simulation for the popu- Util i zati on of f1 at f i sh caught by Oregon 1 ati on of Engl i sh sol e of f the Oregon and t rawl e rs in 1974. Informat iona 1 Report. ifashington coast. OregOn Uepartment Of FiSh and Wildlife.

Hayman, R.A. 1978. Environmental fluc- Tester, P Aog and A G. Carey, Jr. In tuation and cohort strength of Dover sole preparation. Moult classes, size at Microstomus acificus! and English sole rfaturity and population size structure of !faaro r s ve u us .S. thesis. Oregon ChipneCeteS tanneri Rathbun BraChyura: Sta e ns vers> ty. ~naguae o f t s southern ltregon coast.

Hayman, R.Ae o and A.V. Tyl er. 1980. Thompson, G.G. 1979o A theoretical Environment and cohort strength of Dover framework for understanding aspects of sole and English sole. Trans. Am. Fish. fisheries bioeconomic systems. M.S. the- Soc. 109:54-68. sis. Oregon State University.

Hewi tt, G., H.G. Pearcy, and A.V. Tyler. Tyler, A.Voh and R.A. Hayman. In prepara- In preparation. Movement of English sole tionn. Estimation of stock-recruitment Paro hr s vetulus!: an analysis of the relationShips frOm Surplus prOduCtion ins ore trauuushery off Oregon. Sea models, wi th application To Pacific hali but Grant publication ser ies ~ Oregon State data. University . Tyler, A.Vem and N. Stephenson. In prep- Kreuz, K.F. 1978. Long-term variation in aration. Application of statistical growth of Dover sol e Microstomus cluster analysis methods to otter trawl acificus! and English sole ~aro rys datae ve us ~ . hl.S. ~ ~ ~ thesis. Oregon a e i ty.

Kruse, G.Hen and A.V. Tyler ~ In prepara- tion. A simulation model of English sole ~Parehr s vetulus! recruitment mechanisms.

Mundy. B.C. In preparation. Yearly variation in the abundance and distribution of fish larvae in the coastal zone off Yaquina Head, Oregon, from June 1960 to August 1972. M.S. thesis. Oregon State University .

Pearcy, W.Goo and E.E. Krygier. In prep- aration. Distribution, abundance, and growth of 0-age English sole in estuaries

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