the state of the science - forage fish in the california current

7/30/2019 The State of the Science - Forage Fish in the California Current.

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O C E A N S C I E N C E

scientiic report

JAnU ArY 2013

t sa s:

Forage Fish in theCaliornia Current.


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2 P E W O C E A N S C I E N C E : S C I E N T I F I C R E P O R T

exuv suay

In the Caliornia Current (CC), a diversegroup o orage shes play an importantand oten underappreciated role in themiddle o the ood web. These spe-cies, such as Pacic sardine and north-ern anchovy, eat plankton and supportpredators such as whales, sea lions, seabirds,sharks, salmon, and tuna. The availabil-ityabundance, size, timing, and locationo orage sh has been shown to aectpredators with declines in productivityand survival when availability decreases.Meanwhile, sheries targeting orage shes

may indirectly or directly compete withpredator needs. Although some orage share consumed by humans, many are usedor nonood products such as animal eed,pet ood, and shing bait.

Forage sh populations are inuenced byenvironmental variation, natural processes,and human activities such as shing, coastaldevelopment, and pollution. They are alsosubject to natural population cycles. Theseactors are not always well-understood andare dicult to incorporate into most man-agement approaches.

Many orage sheries are not managed,and o those that are, management rarelyconsiders such actors as predator needsand environmental uctuations. Traditionalsheries management based on maximumsustainable yield, or the largest catch thatcan be taken rom a species stock over anindenite period, is not appropriate or preypopulations like orage sh because it doesnot account or the larger role they play in

ecosystems.

Ecosystem-based sheries management(EBFM), which ocuses on the role o sh-eries in the context o an overall ecosystemrather than on single species, has beenproposed as a way to, among other things,emphasize the role o orage sh in theecosystem and consider catch on a second-ary basis. Some ederal and state agenciesare starting to implement EBFM, althoughmovements are slow. Complementaryapproaches include precautionary manage-ment, sheries closures, and orage reservesor predators, which may be tailored to

predator needs in terms o prey diversity,abundance, distribution, size, seasonality,and/or interannual variability.

There is economic and ecosystem researchthat indicates leaving more orage sh in theenvironment to support predator sheriesmay be more valuable than removing themin orage sheries. In upwelling systems likethe CC, orage sh may be more valuableas prey than as catch.

Several large-scale studies have alsorecently suggested thresholds o orage shbiomass that should remain in the oceanor predators. Under the increasing arrayo threats to orage sh, eorts should bemade to control those actors that we can,such as shing, to enable the maximumresilience possible to actors that we cannoteasily control, such as climate change. Thisapproach is important or the health oorage sh stocks themselves as well as thepredators that rely on those sh.


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T H E S T A T E O F T H E S C I E N C E : F O R A G E F I S H I N T H E C A L I F O R N I A C U R R E N T

u . Forage sh play an important role inmarine ood webs, occupying the middle othe ood web. They largely eat plankton andin turn support a diverse group o predators,including commercially important species likesalmon and tuna.

idu

The Caliornia Current, which runs romBaja Caliornia in Mexico to CanadasBritish Columbia, may be the worlds moststoried sliver o ocean. In the early 1940s,sardine boats out o Monterey, Caliorniahauled in 700,000 tons a year and providedthe backdrop or John Steinbecks nostalgicCannery Row. The Pacic sardine sherysubsequently suered a spectacular crashby the late 1940s.

Globally, orage shes are some o the mostabundant and well-known in the world,

including species like sardine and anchovy,but also many other important, though lesswell-known, species. Forage shes play animportant role in marine ood webs, occupy-ing the middle o the ood web (Figure 1);they largely eat plankton, and are in turneaten by larger predators. Forage speciescan also include invertebrates such as squidand krill and juveniles o some predatorysh such as rocksh. Although there arevarious ways to dene orage species, orthis document, we consider small open-ocean schooling sh that remain at thesame level in the ood web or their entirelie cycle, and due to their size and abun-dance are important as orage during theiradult lie-phase.

Forage shes oten undergo populationcycles, the most amous o which is thedecadal-scale uctuations, or boom-bust cycling, o sardine and anchovy(Schwartzlose et al. 1999, Chavez et al.2003). For this reason, as well as other

actors dictating orage availability, manytypes o orage shes are necessary tosustain important predators such as salmonand seabirds that rely on them (Thayer andSydeman 2009, Daly et al).

Fisheries targeting orage sh may competewith predators, either directly or the samesh or indirectly by altering ood webs and

ecosystem unctioning (Trites et al. 1997,Coll et al. 2008). Many orage sheries arenot managed, and o those that are, thelarger orage community, predator needs,or environmental uctuations are rarelytaken into account. This is despite concernsresearchers have raised about the eectso shing on seabirds (Jahncke et al. 2004,Fredericksen et al. 2008, Pichegru


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et al. 2010), pinnipeds (DeMaster et al.2001, Matthiopoulos et al. 2008), andcetaceans (Constable et al. 2000, Bearziet al. 2008). Recent studies have suggestedorage thresholds needed to sustain preda-tors that would necessitate reductions incurrent levels o shing (Smith et al. 2011,Cury et al. 2011, Pikitch et al. 2012).

the role o orAge ish in

the cAliorniA cUrrent

The Caliornia Current (Figure 2) ischaracterized by a narrow continentalshel with a steep slope, along which themain current ows and across which windscause coastal upwelling (Figure 3), particu-larly important near capes and headlands(Chavez et al. 2002, Checkley and Barth2009). Interannually, the timing o upwellingis variable but generally strongest during

the spring and summer, leading to nutrientenrichment and cool temperatures in theoceans surace layer as water rises romthe depths (Chavez et al. 2002, Bogradet al. 2009). High nutrient levels uel plank-ton photosynthesis and growth, providingthe base or the ood web. The eect oupwelling is altered during El Nio SouthernOscillation (ENSO) events when the oceansurace mixed layer deepens, leading towarm, nutrient-poor surace waters andan inux o subtropical or tropical species(Chavez et al. 2002). There are also longer-term ocean uctuations driving marine pro-ductivity, represented by the warm or coolphases o the Pacic Decadal Oscillation(PDO) (Mantua and Hare 2002, Checkleyand Barth 2009).

There are many orage shes in the CC,including the northern anchovy (Engraulismordax; see anchovy case study), Pacicsardine (Sardinops sagax; see sardine casestudy), Pacic herring (Clupea pallasii; see

u . The Caliornia Current (CC)spans temperate waters rom Baja Caliorniato British Columbia.


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herring case study), Pacic saury (Cololabissaira), lanternsh (Myctophidae), Pacicsandlance (Ammodytes hexapterus), andsmelt (Osmeridae; see smelt case study),along with many other less-well-knownspecies. These orage shes support adiverse predator assemblage o whales anddolphins, seals and sea lions, seabirds andsea turtles, sharks and rays, and large shes

such as salmon and tuna. Some orageshes occur throughout the CC, whileothers are more important in the north(e.g., sandlance in Washington) or south(e.g., grunion in Southern Caliornia). Someother ecosystems, such as the HumboldtCurrent o Peru, are dominated by a ew oreven just one orage sh species and have amid-ood web bottleneck, or wasp-waist,structure (see Cury et al. 2000). The degreeo orage diversity in the CC arguablyprecludes such a structure, although sardineand anchovy are dominant species.

Although little is known about many o theorage shes in the CC, some species suchas sardine and anchovy support commer-cially important sheries and are managedand studied extensively. There is consider-ably less data on noncommercial speciessuch as sandlance, smelt, and lanternsh.Even or the more well-understood species,

much is still unknown about mechanismsdriving population dynamics and the extentto which predators depend on them. In partthis is due to sampling di culties and theconsiderable seasonal and year-to-yearvariability o these species.

Availability o orage shes has beenshown to directly aect marine predators.

For instance, prey availability inuences dis-tribution, diet, oraging behavior, ospringgrowth, breeding success, adult body condi-tion and survival, and population change inseabirds (Anderson et al. 1982, Rindoret al.2000, Jahncke et al. 2004, Davis et al. 2005,Craword et al. 2006, Craword et al. 2007,Piatt et al. 2007, Thayer and Sydeman 2007,Frederiksen et al. 2008, Field et al. 2010,Pichegru et al. 2010) and marine mammals(Kieckheer 1992, Aguilar 2000, Jaquet etal. 2003, Soto et al. 2004, Soto et al. 2006,Womble et al. 2005, Womble and Sigler

2006, Hlista et al. 2009, Sigler et al. 2009,Winter et al. 2009, Patrician and Kenney2010, Miller et al. 2011). For salmon, preyavailability inuences growth and survival(Brodeur 1991, Daly et al. 2009, Weitkampand Sturdevant 2008). Tuna distributionsvary widely and track orage sh (Laurs et al.1984, Polovina 1996, Kitagawa et al. 2007).

Prey availability reers to not only orageabundance, but also size classes, timing,and geographic considerations that maydetermine predators ability to nd andconsume prey. Salmon, or example, rely ondierent orage shesincluding anchovy,sardine, herring, sandlance, and smeltatdierent times o the year and at variousstages o their lie cycle (Daly et al. 2009,

Merkel 1957). Salmon have prey size limita-tions as small smolts entering the ocean,yet this may be one o the most importantperiods determining young salmons surviva(Koslow et al. 2002, Logerwell et al. 2003,MacFarlane 2010). Seasonal availability oorage may also be key or other predators(Willson and Womble 2006); herring hasbeen ound to occur in 90 percent o Stellersea lions diet at certain locations duringthe herring spawning period (Womble andSigler 2006). Migration o sur scoters par-allels the northward progression o herring

spawning events along the West Coast(Lok et al. 2012).

Predator-prey mismatch, when the timing ospatial distribution o orage availability di-ers rom that o predator needs, is becom-ing common with climate change (Bertramet al. 2001, Edwards and Richardson 2004,Durant et al. 2007, Sydeman and Bograd

u . Upwelling occurs when wind drivescooler, dense, and nutrient-rich water towardsthe ocean surace, replacing the warmersurace water. Coastal upwelling in the CCis variable but generally strongest during thespring and summer, oten leading to nutri-ent enrichment and cool temperatures in theoceans surace layer. High nutrient levels canuel plankton growth.

winds

continentalshel


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2009, Watanuki et al. 2009, Dorman et al.2011). Temporal examples include variationin herring spawning initiation o more thanthree months, leaving predators such asSteller sea lions with ewer or lower-qualityprey options during the lean winter monthsor during spring, when preparing or breed-ing (Willson and Womble 2006). Localizeddepletion o orage shes due to shing is

also a concern (Tasker et al. 2000). Spatially,breeding seabirds, seals, and sea lions returnto ospring at land-based colonies and thushave limited oraging ranges, during whichtime localized prey depletions could be del-eterious (Croll and Tershy 1998, Wanless etal. 1998, Daunt et al. 2008, Wol and Mangel2008, Plagnyi and Butterworth 2012).More research is needed in this area.

Forage species richness is key in localmarine communities. A diverse orageassemblage can provide the redundancy

needed or prey-switching opportunities,especially given variability in abundance,size, distribution, or time as discussedabove. Despite this, the specic orageneeds o top predators have not beenadequately addressed in management.The diets o some dependent predatorshave not been suciently studied, particu-larly i such studies are logistically challeng-ing, as is oten the case or cetaceans (e.g.,Stroud et al. 1981). Nevertheless, there isan abundance o predator-diet data avail-able or the CC (e.g., Sydeman et al. 2001,Duault et al. 2009, Orr et al. 2011).

orAge isheries in the

cAliorniA cUrrent

The schooling behavior o orage shallows them to be easily caught, translat-ing into relatively low operating costs orsheries and thus relatively cheap sh andsh products or consumers. Forage sh arecaught within the exclusive economic zones

(EEZ) o Canada, Mexico, and the UnitedStates, as well as in international waters out-side these EEZs. Forage sh are generallytargeted with round-haul gear includingpurse seines, drum seines, and lampara nets(Figure 4). These species are also takenincidentally with trawls, gillnets, trammelnets, trolls, pots, hook-and-line, and jigs.

Although some orage sh are consumedby humans, many are used or nonoodproducts such as animal eed, pet ood,aquaculture, and bait or shing. Morethan 36 percent o the global sh catchis destined or nonood uses (Tacon andMetian 2009), and demand is increasing(Naylor et al. 2000). The exact propor-tions o orage sh usage in the CC are not

well-documented.

Historically, most sh that could be caughtwere used as human ood sources globally;the reduction o sh to shmeal and oil orindirect use is a relatively recent develop-ment. The sh oil industry began in the19th century when seasonally abundantcatches o herring and sardines could notbe absorbed by local markets in Europeand North America (Watson et al. 2006).The oil was used or lubricating machinery,leather tanning, soap production, and other

nonood products, and the byproducts osh oil production were used as ertilizer.The production o shmeal or animal eedbegan in the early 20th century, includingrom sardines in Caliornia (Watson et al.2006).

Pacic sardine (see sardine case study) iscurrently one o the most lucrative sheriesin Caliornia. It is also caught o the coastso Oregon and Washington in signicantamounts (Caliornia Department o Fishand Game [CDFG] 2012, Hill et al. 2010b).However, sardine abundance may bedeclining (Wespestad and Maguire 2012,Zwolinski and Demer 2012). The status oanchovy (see anchovy case study) popula-tions is largely unknown, although limiteddata suggest that populations o thesesh are depressed (Brodeur et al. 2006,Bjorkstedt et al. 2011, Fissel et al. 2011).

Herring (see herring case study) also sup-port very high-value sheries in the CC,much o it or roe destined or the Japanese

market. Herring populations, however, arealso at a low level, probably due to a combi-nation o human and environmental actors(Landis et al. 2004, CDFG 2012, Wespestadand Maguire 2012).

There are economic and ecosystem argu-ments that avor leaving more orage shin the environment to support predator sh-eries versus removing them in orage sher-ies. Sardines, or example, are valuable asood or commercially important predatorsin the CC, particularly salmon. The eco-system value o orage sh would increasewith consideration o predator species

such as seabirds and marine mammals thatare not exploited but have extraordinaryaesthetic and ecotourism value (Hannesonet al. 2009, Hannesson and Herrick 2010).Thereore, in upwelling systems such as theCC, orage sh are generally more valuableas support to other valuable sheries than ascatch themselves (Pikitch et al. 2012).

chAllenges or orAge ish in


eva vaayThe CC has historically had large naturaluctuations in oceanographic actors andrelated orage sh abundance (Baumgartneret al. 1992, Chavez et al. 2003). The bio-logical mechanisms causing these popula-tion cycles are still unclear but probablyare related to current ows, upwelling,and associated sea surace temperature(MacCall 2009). The cyclical pattern oabrupt changes in orage sh populationssuggests that the driver is a combinationo several physical and ecological actors(MacCall 2009). For example, anchoviesand sardines have long been consideredto ecologically replace each other as theenvironment uctuates. However, recentresearch suggests that the ecologicalmechanisms behind out-o-phase uctua-tions may be much more complex than asimple replacement (Barange et al. 2009).

ca a

Climate change is distinct rom envi-ronmental variability in that it reers to

changes in the mean and/or variabilityo ecosystem properties (such as tem-peratures and sea levels) that persist oran extended period, typically decades orlonger (Intergovernmental Panel on ClimateChange [IPCC] 2007). Eects can beseen on physical ocean processes andhabitats, as well as on species interactions,including cycles o orage sh dynamicsand predator responses.


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Incidence o nonnative species is increas-ing and can also have a powerul eecton coastal ood webs and undamentallyalter sh distributions. For example, anintroduced clam (Corbula amurensis) in theSan Francisco Bay eliminated summer-longphytoplankton blooms starting in 1987,causing a shit in anchovy distribution out

o the estuary that was a direct response toreduced ood availability (Kimmerer 2006).A more pervasive example in the CC is the

jumbo squid (Dosidicus gigas) rom tropicalwaters, which has been observed in substan-tial numbers in the subtropical CC sincethe 1998 ENSO warm-water event(Pearcy 2002, Brodeur et al. 2006, Fieldet al. 2007). It is a voracious predator omany orage shes such as anchovies andsardines (Field et al. 2007).

Improvements in shing technology suchas acoustics and modernized gear haveincreased the vulnerability o schoolingorage sh (Beverton 1990). Furthermore,shing makes sh populations morevariable than would occur naturally andmore susceptible to climate perturbations(Hsieh et al. 2006, Anderson et al. 2008).Susceptibility may increase because shpopulations are less abundant, have trun-cated age structures (ewer older individu-als), or are depleted locally. The latter twoactors are potentially just as important asabundance in maintaining long-termsustainable population levels (Berkeleyet al. 2004, Anderson et al. 2008).

Sardines provide one example. At lessthan 5,000 tons (MacCall 1979), sardineabundance was probably lower ater the1960s population crash than at any timein the previous 2000 years, even duringperiods o natural low abundance, whichwere historically on the order o roughly400,000 tons (Baumgartner et al. 1992;

see sardine case study). Another examplecomes rom herring along the Paciccoast, which are experiencing truncatedage structure and localized depletions osubpopulations (Stick and Lindquist 2009,CDFG 2012; see herring case study). Thesechanges may threaten the ability o theoverall herring metapopulation to respondto harmul changes, because it has lost valu-able genetic and behavioral diversity. For

u 4. Forage sh are generallytargeted with round-haul gear

including purse seines (top), drum seines,and lampara nets (bottom).


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example, remaining subpopulations may beat a genetic disadvantage or certain typeso adaptation, may be more susceptible todisease or parasites, or may not have theability to shit spawning times to accountor climate changes or spawning locationsin response to local habitat degradation.These could compromise herring at a meta-population level or even eventually render

the metapopulation obsolete. The beneto diversity among subpopulations, whichallows some to persist in the ace o change,is termed the portolio eect (Berkeleyet al. 2004, Anderson et al. 2008, Schindleret al. 2010, Carlson and Satterthwaite 2011).

caa dv

Urban, industrial, agricultural, oraquaculture development may directlydegrade coastal habitat. This may haveparticularly negative inuences on speciesthat spawn in beach, intertidal, or subtidal

areas (see smelt case study). Oshorerenewable energy and desalination projectsare also increasing rapidly o the WestCoast. For example, desalination projectsmay result in changes to local water owand salinity levels, and entrainment olarvae, eggs, and plankton in pumps andturbines (San Francisco Bay Conservationand Development Commission 2005).

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Oil spills, ocean dumping, industrialdischarge, and other chemical pollution arecontinuing threats or sheries (Colodeyand Wells 1992, Sindermann 1996, Carlset al. 1999, Landis et al. 2004, Incardonaet al. 2012; see herring case study). Increasesin runo are anticipated due to expandinghuman populations, coastal development,and agriculture. Noise pollution could alsobe a problem; trauma rom high-intensity,low-requency sounds has been observedrecently in cephalopods (Andr et al. 2011)and in sh (McCauley et al. 2003).

Together, these inuences may threaten thewhole orage base (all species combined)or just specic species, cause widespread orlocal eects. They could increase variationin orage sh dynamics, by urther reducingpopulation numbers, diversity, and the abil-ity o sh to withstand harm.

orAge ish mAnAgement in


Forage shes are managed within the U.S.EEZ, spanning the jurisdictions o ederalor state agencies and Native Americantribes. Federally, the Coastal Pelagic SpeciesFishery Management Plan (CPS FMP)includes sardines and anchovies. The Pacic

Fishery Management Council (PFMC)and the National Marine Fisheries Service(NMFS) have ederal jurisdiction in the CC.

Sardines are actively managed, meaninglandings and markets are substantial enoughto warrant annual assessment o stockstatus and shery management. Anchoviesare monitored only or potential elevationto active management, because they areassumed to now be landed in low numbers.Herring was recently added to the CPSFMP as a new designation, ecosystem

component species. While this designationinitiates monitoring o herring as incidentalcatch, there are still no ederal restric-tions on shing or ecosystem-componentspecies. Thereore, herring managementis let to the states o Caliornia, Oregon,and Washington. Except or species listedunder the Endangered Species Act (e.g.,the threatened smelt species eulachon[Thaleichthys pacicus]), most orage shesin the CC are not ederally or even activelymanaged at the state level. Examplesinclude most smelts, sandlance, lantern-shes, saury, and others.

ca a f aa

Traditional stock assessment techniquesare oten used with the orage sh thatare managed in the CC; however, theseassessments do not perorm well or pelagicorage sh. For example, basic managementinormation, such as reliable estimates opopulation size, is not available or mostorage shes, even species with active sh-eries. In addition, most sheries manage-

ment ocuses on individual species and doesnot consider multiple species simultane-ously, which is problematic given the criticalecological role o orage sh as prey.

Furthermore, populations o short-livedorage sh can grow or decline quickly inresponse to climatic shits, but mecha-nisms driving these dynamics are not

well-understood (MacCall 2009). Fishingitsel also increases populations susceptibil-ity to climate changes (Hsieh et al. 2006,Anderson et al. 2008), yet managementresponse oten lags behind these biophysi-cal changes.

The catchability o orage sh mayincrease or remain constant even as a stock

declines rapidly, due to their schoolingnature and their vulnerability to modernshing technology (Beverton 1990). Thus,declines in stock size may not be apparentbased on commonly used catch-per-unit-eort statistics.

Traditional sheries management ocuseson maximum sustainable yield through time,yet this concept is not appropriate or preypopulations, or populations that undergonatural cyclical uctuations, or whenconsidering eects to other species in the

ecosystem (Larkin 1977, Legovic et al. 2010,Zwolinski and Demer 2012). High catchrates on short-lived species also mean thaterrors or uncertainty in setting catch ratescan have particularly severe consequences(Pinsky et al. 2010). Pretty good yield hasbeen recently suggested as an alternativeand is dened as 80 percent o maximumsustained yield (Hilborn 2010), although thisstill does not account or any interactionswith other species.

Natural mortality (e.g., predation, dis-ease, starvation) is notoriously dicult toestimate reliably; yet inaccurate naturalmortality rates may result in very mislead-ing estimates o stock status providedto managers (Vetter 1998, Lee et al.2011). Specically, traditional assessmentapproaches that underestimate the magni-tude and dynamic nature o natural mortal-ity or orage shes lead to biomass andyield projections that are overly optimistic(Tyrrell et al. 2011). Moreover, dierentsurvey methods result in size selectivity

o orage sh, or bias towards certain sizeclasses, that is dicult to establish and canintroduce additional error into stock assess-ments (see Hill et al. 2010a). Finally, preda-tor needs are not adequately addressedin most current management scenarios(Pikitch et al. 2004, Tyrrell et al. 2010).


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cAse stUDY: northern AnchoVY Engraulis mordax

Anchovies consist o two subspecies inthe CC: Engraulis mordax mordax, whichranges rom British Columbia to BajaCaliornia and was recently also oundin the Gul o Caliornia; and E.mordaxnanus, which is ound in the bays oCaliornia. Usually seen in coastal waterswithin about 18 miles (30 kilometers)rom shore, anchovies orm large, tightlypacked schools. E. mordax mordaxisdivided into northern, central, and south-ern subpopulations. The central sub-

population was once the ocus o large,commercial sheries in the U.S. andMexico. Most o this subpopulation islocated in the Southern Caliornia Bight.Those ound north o Cape Mendocino,Caliornia, are considered the northernstock, and the southern stock is oundentirely in Mexican waters.

Anchovies have the ability to spawnthroughout the year. In Caliornia, peakspawning occurs rom February to Apriland in Washington rom mid-June tomid-August (Hunter and Macewicz 1980,Laroche and Richardson 1980). The lastcomprehensive stock estimates or thecentral subpopulation were made in 1995,ater population declines and the down-turn o the shery (Jacobson et al. 1995).Recent population estimates, althoughlimited by available data types and surveyand analysis methods (see Jacobsonet al. 1994, Fissel et al. 2011, Simmonds2011), indicate a generally depressedanchovy population (Fissel et al. 2011).

Only two scientic assessments havebeen completed or the northern stock,the second o which suggests there wasa signicant decline by 1995 (Richardson

1981, Emmett et al. 1997). Other datasources also suggest that these anchovypopulations remain low (Brodeur et al.2006, Bjorkstedt et al. 2011).

Despite limited inormation, commer-cial catch in the CC increased in themid-2000s (PFMC 2010). Furthermore,catch outside o commercial sheries ispoorly documented and underreported(PFMC 2010). In 2005, or example,anchovy mortality rom bycatch, live bait,

recreational, incidental, and internationalsheries totaled at minimum more than65 percent o commercial U.S. landings(Caliornia, Oregon, and Washington[calculated rom PFMC 2010]).

Anchovies are o high importance topredators due their relatively small size,inshore distributions, and almost year-round availability. More than 50 predatorspecies in the CC consume anchovies,including important commercial andrecreational species. The seasonal dieto Chinook salmon, or example, can beas much as 90 percent anchovy in someyears (Merkel 1957).

Increases in commercial and other land-ings despite 15 years o low anchovyproductivity and high dependence opredators could put the anchovy stock,valuable predators, and the larger ecosys-tem at risk.

rAnge

high concentrAtion rAnge


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cAse stUDY: pAciic sArDine Sardinops sagax

When the population o Pacic sardinesis large, this sh is abundant rom the tipo Mexicos Baja Caliornia to southeast-ern Alaska and throughout the Gul oCaliornia. There are three Pacic sardinesubpopulations in the CC with spawn-ing centers in the Gul o Caliornia,Baja Caliornia inshore and southern tocentral Caliornia oshore (Smith 2005,Hill et al. 2010b). The central Caliorniasubpopulation is most relevant to theCC as a whole. This population spawns

rom January to June, and larger adultsmigrate in the spring to Washington andBritish Columbia.

Sardine populations naturally uctuatein abundance roughly every 50 years(Baumgartner et al. 1992), driven mainlyby large-scale climate uctuations(Chavez et al. 2003, MacCall 2009), butthese natural up and downs in populationare also exacerbated by shing pressure(MacCall 2009, Zwolinski and Demer2012). Geologic records o sh scalesdeposited in the Southern CaliorniaBight indicate that unshed sardinepopulations uctuated naturally betweena low o 400,000 tons to many millions otons (up to 16 million tons [Baumgartneret al. 1992] ). In the 1930s and 1940s,sardines were the largest single-speciesshery in the Western Hemisphere andwere largely unregulated (Zwolinski andDemer 2012). The population went rommore than 3 million tons in the 1930sto less than 5,000 tons in the 1960s

(MacCall 1979). Sardine biomass did notincrease again until the 1980s and 1990s,and the shery resumed; biomass peakedat more than 1.5 million tons in 2000 andhas subsequently trended downward to

roughly 500,000 tons in 2010 (Hill et al.2010b), with renewed ears o a popula-tion crash (Zwolinski and Demer 2012).

The sardine shery has been ederallyregulated since 2000. Some manage-ment measures are relatively progressive,such as an environmental harvest-controlrule, although there are opportunities tourther improve management (Jacobsonet al. 2001, Smith et al. 2005, Emmett etal. 2005, Hill et al. 2010b, McClatchieet al. 2010, PFMC 2010, Zwolinskiand Demer 2012). For example, withinthe U.S. EEZ, sardines are caught bycommercial, live bait, and recreationalsheries in Caliornia, Oregon, andWashington. Sardines are also taken asincidental catch in the Pacic mackerel,squid, and anchovy sheries. The ederalharvest quota or sardine includes set-asides or research, incidental catch, andmanagement uncertainty. The set-asideor incidental catch (3,000 tons) does notappear to have been exceeded recentlyin squid, anchovy or Pacic mack-erel sheries (PFMC 2010); however,there are no set-asides or live bait andrecreational sheries. Caliornia live baitsheries alone regularly exceeded 3,000tons annually in the past decade (PFMC2010). Thus the cumulative humanremoval o sardines rom the ecosystemis not ully addressed in the commercialharvest quota.

Beyond the U.S. EEZ, sardines are

caught in Mexican and Canadian sher-ies. International catch pushed totalsardine harvest above the ederal over-shing limit in 2009 (Hill et al. 2010b),highlight ing the di culty o managing

sh populations spanning internationalboundaries. Furthermore, overshingmeasures specied in the CPS FMPwere not implemented, despite the actthat this occurred during the recentsardine population decline.

Many predators rely on sardines, includ-ing Chinook and coho salmon, Pacic

hake, and jack mackerel (Merkel 1957,Emmett et al. 2005). Seabirds, seals, sealions, whales, dolphins, and sharks alsoorage extensively or sardines (Baltz andMorejohn 1977, Stroud et al. 1981,

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T H E S T A T E O F T H E S C I E N C E : F O R A G E F I S H I N T H E C A L I F O R N I A C U R R E N T 1

Velarde et al. 1994, Clapham et al.1997, Emmett et al. 2005, Becker andBeissinger 2006, Weise and Harvey2008). Caliornia sea lions alone, orexample, may consume the equivalento roughly 10 percent o total sardinebiomass in central Caliornia (Weise andHarvey 2008). Federal sardine manage-ment or the U.S. West Coast includesa harvest cut-o o 150,000 tons, whichtheoretically includes stock or potentialrebuilding at low population sizes, as well

as sardines as orage or dependent pred-ators (PFMC 2010) or each year underall environmental conditions. Furthersynthesis o CC predator orage require-ments is much needed to determine theadequacy o this threshold, given theimportance o sardines as orage.

There are very ew sheries stock assess-ments or harvest policies that incorporateany measure o environmental variability(except see Schirripa et al. 2009). Thesardine ederal harvest policy is relativelyunique because a proxy or environmen-tal variability, a three-year average osea surace temperature at the ScrippsInstitution o Oceanography pier inLa Jolla, Caliornia, is used as oneparameter in the ormula or establish-ing the harvest quota (Hill et al. 2010b).Although a recent study suggestedproblems with this specic approach(McClatchie et al. 2010), environmentalactors are clearly important or sardinestocks. Thus, this general approach

should continue to be pursued, even ithe specics need to be modied.

cAse stUDY: smelt Osmeridae

The true smelts (Osmeridae) areseveral species o small silvery sh,including whitebait smelt, sur smelt,night smelt, longn smelt, and eula-chon. Smelt are common year-roundresidents in many nearshore areas romCaliornia to Alaska; however, their ullranges are not well-documented. Theyare relatively small, short-lived sh,reaching about 8 to 12 inches (20 to 30centimeters) in length and surviving orthree to ve years. Some smelt have

an entirely marine/estuarine lie history(sur, whitebait, night smelt), while others(such as eulachon and longn smelt) areanadromous. Eulachon is ederally listedas threatened under the EndangeredSpecies Act, and there is an active peti-tion to list longn smelt.

Data on smelt lie history and particularstocks are largely lacking. There arecurrently no population size estimatesor most smelt species, including white-bait and sur smelt, although these areamong the dominant pelagic schoolingshes caught in research surveys in theOregon-Washington region (Brodeuret al. 2003). Environmental inuenceshave been demonstrated or whitebaitsmelt in Oregon. For example, poor bodycondition is likely a result o poor oceanconditions, such as reduced upwelling,that result in lower biomass and poorcondition o zooplankton prey (Litz etal. 2010). It is not known exactly whereand when whitebait smelt spawn, but

the occurrence o larvae in estuariesduring all suggests that they may belate summer spawners on subtidal banks(reviewed in Litz et al. 2010). Smelts are

particularly important orage or preda-tors in the central to northern CC.

Commercial and recreational sher-ies occur on sur smelt populations atmany sites throughout Oregon andWashington (Bargmann 1998). Adequateshery statistics are lacking or smelts,in spite o their ecologically data-poorstatus and local importance. Recreationalcatch may actually exceed that o com-mercial catch in some instances, perhaps

because unlike most other orage shspecies, most smelt are used or humanconsumption (Bargmann 1998).


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cAse stUDY: pAciic herring Clupea pallesi

Pacic herring have long been exploitedby humans and are consumed by naturalpredators. Herring have been animportant resource or Native Americangroups in the Pacic Northwest orcenturies (Hourston and Haegele 1980,Gobalet and Jones 1995, Bargmann1998). Commercial sheries have repeat-edly sprung up and crashed along theU.S. West Coast. A small commercialsport bait shery in south Puget Sound(Stick and Lindquist 2009) and small

commercial roe, eggs on kelp, and reshherring sheries in San Francisco Bay(CDFG 2012) are the only signicantsheries remaining.

Pacic herring are ound throughoutthe coastal zone rom northern BajaCaliornia around the North PacicRim to Korea. They spawn betweenOctober and April in shallow parts obays and inlets, preerably onto marinevegetation or subtidal rocks, but man-made structures are also used.

Threats to herring in the CC includelarge population declines due to climateand overexploitation, truncated agestructure, localized population deple-tions, degraded spawning habitat, andoil and other chemical pollution(Zebdi and Collie 1995, Toresen andstvedt 2000, Landis et al. 2004, Stoutet al. 2001, Stick and Lindquist 2009,CDFG 2012, Incardona et al. 2012,Wespestad and Maguire 2012). The

spawning habitat o what was the largestWashington herring population, CherryPoint in Puget Sound, is now centered inan area o industrial activity and urbandevelopment (Stout et al. 2001). Thelargest remaining Caliornia population,in urban San Francisco Bay, recentlysuered eects o an oil spill (Incardona

et al. 2012) presumably reducing alreadydepressed numbers (CDFG 2012). Otherhistorically large herring spawning popu-lations in Caliornia, such as Tomales Bay,are also signicantly reduced (Bartling2006).

Some herring populations are distinct,not mixing with neighboring popula-tions due to geographic or behavioraldierences such as varied spawningtimes. Where genetic dierences have

not been established, populations maydemographically be characterized as ameta-population. Understanding localpopulation structure, however, is essentialor the preservation o spawning poten-tial and genetic and lie history diversity(Gustason et al. 2006).

Pacic herring have been documentedto live as long as 15 years, though ewexceed 9 years (Ware 1985). WhileCC stocks included long-lived sh inthe 1970s, herring older than 4 or 5 arenow rare, and the median age is 2 to 3(Hershberger et al. 2005, Gustason et al.2006, Mitchell 2006, Stick and Lindquist2009, CDFG 2012). This change isprobably largely due to intense shing.Other actors include predation andincreased rates o pathogenic inectionin older sh, which may contribute bothdirectly and indirectly (through increasedpredation) to mortality (Hershbergeret al. 2002, Stick and Lindquist 2009).Declining longevity may urther harm

herring populations, or example byreducing the quantity and quality oeggs (Hay 1985, Ware 1985), shorteningthe spawning season and thus decreas-ing the populations overall reproductivepotential (Wright and Trippel 2009).

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iv a f aa

When assessing sh population status oruse in management decisions, the inclusiono ecological interactions is central to anecosystem-based perspective. This is nota new concept (e.g., May et al. 1979), yetincorporating basic ecological processessuch as predation and competition into sh-eries stock assessments is still uncommon

(Link 2002, Tyrrell et al. 2011). While thereare movements toward EBFM at the ederaland state levels, they are nascent, slow, orimplemented in a piecemeal ashion (Fieldand Francis 2005, Ruckelshaus et al. 2008,Halpern et al. 2010). Moreover, the degreeto which proposed sheries ecosystemplans, one o the key approaches to imple-menting EBFM, are enorceable is unclear.Regardless, a more ecosystem-centric man-agement approach by denition is holisticand includes multiple considerations.

One important consideration in EBFM,a precautionary management approach,emphasizes the role o orage sh in theecosystem and considers catch secondarily.This eectively shits the burden o prooto show that a given shing level is saebeore allowing it. Such an approach is espe-cially important in data-poor instances or inthe ace o scientic uncertainty (Pikitchet al. 2004, Curtin and Prellezo 2010).

Time and/or spatial sheries closures canprotect spawning sh aggregations orhotspots o predators and prey, and, moregenerally, lie history characteristics andbiodiversity (Babcock et al. 2005, Fieldand Francis 2005, Hyrenbach et al. 2000,Ruckelshaus et al. 2008, Santora et al.2011). Limitations on shery gearsuch asallowable gear types, net length, and meshsizeare important in protecting habitat,minimizing bycatch, and avoiding harvest-ing o sh beore they reach ull maturity(Belgrano and Fowler 2011).

The nature, strength, and changes inecological processes, such as predationand competition, inuence single-speciespopulation dynamics as well as ecosystemunctioning (Field and Francis 2005, Tyrrellet al. 2011). Environmental variation urtherinuences single-species dynamics andinteractions among species. Environmentaleects include long-term (e.g., warm/cool

marine decadal regimes) and short-term(e.g., ENSO) uctuations, as well as trend-ing temperatures and increasing variabilityassociated with climate change (Field andFrancis 2005, Curtin and Prellezo 2010,Belgrano and Fowler 2011). Environmentaleects, however, are also rarely incorpo-rated into sh population assessments orsheries management decisions (except

see Hill et al. 2010b, Schirripa et al. 2009;see sardine case study). EBFM should alsoconsider risks to sh populations and theecosystem rom human sources such ashabitat destruction and pollution (Pikitchet al. 2004, Curtin and Prellezo 2010; seeherring and smelt case studies).

In addition to integrating predator eectsinto sh population assessments, EBFMshould take the needs o predators intoaccount in relation to degree o shing(Smith et al. 2011, Cury et al. 2011, Pikitchet al. 2012). Approaches include precaution-ary management, sheries closures, andorage reserves or predators, which may beapportioned to predator needs in terms oprey diversity, abundance, distribution, size,seasonality, and/or interannual variabilitydue to climate or other actors.

Several large-scale studies have recentlysuggested thresholds o orage sh biomassthat should remain in the ocean or preda-tors. A report o the Lenest Forage FishTask Force (Pikitch et al. 2012) comparedone type o ecosystem model across manysystems globally and ound that approxi-mately 80 percent o unshed orage shbiomass should remain in the water to avoida 50 percent reduction in any dependentpredator population. A study, partiallyunded by the Marine Stewardship Council(Smith et al. 2011), compared three typeso ecosystem models across ve systems.Based on the studys results, the authorssuggest leaving 75 percent o unshedorage sh biomass in the ocean to maintain

ecosystem unction. Cury et al. (2011) useda dierent approach, numerical responsecurves, in seven ecosystems to determinethe threshold o roughly 30 percent o themaximum long-term orage sh biomassbelow which seabirds experience consis-tently reduced and more variable productiv-ity. Each method has its advantages anddiculties, and additional analysis and

synthesis o predator-orage requirementsutilizing a combination o these and otherapproaches will be useul.

When determining catch levels or com-mercial sheries, insucient attention isoten paid to the total human removal oorage sh rom the ecosystem, both byspecies and as a orage group. Such remova

includes nontarget, or incidental, catch,bycatch, live bait sheries, recreational sh-ing, and shing outside the U.S. EEZ thattargets stocks spanning political boundaries(Pikitch et al. 2004, Ruckelshaus et al. 2008,PFMC 2010). Catch outside o commercialsheries can be signicant in some cases(Pikitch et al. 2004), although it is otenpoorly documented and underreportedin the CC (PFMC 2010; see sardine andanchovy case studies). Even ater predatorneeds have been considered, these othertypes o human removal urther reduce the

amount o target orage shes available orcommercial sheries.

Many tools to implement EBFM alreadyexist (Ruckelshaus et al. 2008, Lester et al.2010, Tyrrell et al. 2011, Pikitch et al. 2012).There are some data gaps, such as limitedquantication o relationships between shstocks (Hannesson and Herrick 2010), butmodeling tools to address this issue existor are being developed (see Tyrrell et al.2011 and reerences therein). Other typeso data gaps or stock perormance undervarious conditions might be approximatedrom other systems that are better studied(Dickey-Collas et al. 2010). A wealth opredator diet data exists, although synthe-sis o orage requirements would enableimproved management o shery resourcesin an ecosystem manner.


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sUmmArY

In the CC, sardines are the most heav-ily shed orage sh. Sardines are alsorelatively well-studied and progressivelymanaged, yet there is still much unknownabout their populations, and managementcould be improved, especially in regardto cumulative human removal rom the eco-

system, eects o shing on age structure,West Coast-wide overshing, the environ-mental harvest control rule, and quantitativepredator needs. Even less is known and littlemanagement exists o other orage shes,despite variable levels o shing pressureand high importance to predators.

Recent scientic syntheses, although usingdierent methodologies, reach similar con-clusions: orage sh management worldwideis important but insucient (Smith et al.2011, Cury et al. 2012, Pikitch et al. 2012).

Under the increasing array o threats toorage sh, eorts should be made tocontrol the actors we can, such as shing,to enable the maximum resilience possibleto actors that we cant easily control, suchas climate change. This approach is impor-tant or the health o orage sh stocksthemselves as well as ostering continuedspecies diversity and ecosystem unctioningin the CC. Public and economic ramica-tions o sustainable orage sh managementare substantial, both or predators withno market value (such as seabirds, marinemammals, and threatened and endangeredspecies) and those with considerable marketvalue (such as commercial sheries orsalmon, tuna, and rocksh).


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O C E A N S C I E N C E

scientiic contribUtors

Ju tay, p.D.

Dr. Thayer has worked in the CaliorniaCurrent marine ecosystem or the past 18years. She did undergraduate work in marinebiology at the University o Caliornia,Santa Cruz, and Long Marine Lab, andobtained a doctorate in marine ecologyrom the University o Caliornia, Davis.Dr. Thayer has conducted research on avariety o top marine predators and theirprey in relation to ocean climate. Recentlyshe organized a group o researchers romaround the North Pacic Rim (Canada,Japan, United States) or a comparativestudy o orage sh eaten by a seabird,rhinoceros auklet, ocusing on spatiotem-poral synchronicity in connection with local

to basin-scale marine variability (Thayer etal. 2008). She has also led a collaborativesheries research project in which scienticdata on the diet o salmon are collectedin partnership with local recreational andcommercial shers, synthesizing historicaldata to help understand the recent salmonpopulation crash.

Wa syda, p.D.

Dr. Sydemans career spans nearly threedecades o ecological research. Startingas an intern marine ornithologist workingon the Farallon Islands in 1981, he spent15 years as the director o marine ecologyat PRBO Conservation Science beoreestablishing the Farallon Institute(aralloninstitute.org). Dr. Sydemanobtained his doctorate in ecology romthe University o Caliornia, Davis. He hasconducted a number o plankton-to-pred-ator studies in the Caliornia Current largemarine ecosystem and has written aboutseabirds, marine mammals, and varioussh species. He serves on many scienticpanels, notably as the chair o the Advisory

Panel or Marine Birds and Mammals or theNorth Pacic Marine Science Organizationand Scientic Advisory Committee orimplementation o the Caliornias MarineLie Protection Act. Dr. Sydeman haspresented to state and ederal policymakerson the eects o climate change on marineecosystems and how to best design and usethe nations new ocean observing systems.

o Fisheries and Aquatic Sciences 42(Suppl1):s127-s137.

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Fisheries or orage sh, 1950 to thepresent, p. 1-20. In: Alder, J., and D. Pauly(eds.), On the multiple uses o orage sh:From ecosystems to markets. FisheriesCentre Research Reports 14(3). FisheriesCentre, University o British Columbia[ISSN 1198-6727].

Weise, M.J., and J.T. Harvey. 2008. Temporalvariability in ocean climate and Caliorniasea lion diet and biomass consumption:Implications or sheries management.Marine Ecology Progress Series 373:157-172.

Weitkamp, L.A., and M.V. Sturdevant. 2008.

Food habits and marine survival o juvenilechinook and coho salmon rom marinewaters o Southeast Alaska. FisheriesOceanography17:380-395.

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Winter, A., R.J. Foy, and K. Wynne. 2009.Seasonal dierences in prey availabilityaround a Steller sea lion haulout androokery in the Gul o Alaska. AquaticMammals 35:145-162.

Wol, N., and M. Mangel. 2008. Multiplehypothesis testing and the declining-population paradigm in Steller sea lions.Ecological Applications 18:1932-1955.

Womble, J.N., and M.F. Sigler.2006. Seasonalavailability o abundant, energy-richprey inuences the abundance and diet

o a marine predator, the Steller sea lionEumetopias jubatus. Marine EcologyProgress Series 325:281-293.

Womble, J.N., M.F. Willson, M.F. Sigler,B.P. Kelly, and G.R. Van Blaricom.2005. Distribution o Steller sea lions(Eumetopias jubatus) in relation to spring-spawning prey species in southeasternAlaska. Marine Ecology Progress Series294:271-282.

Wright, P.J., and E.A. Trippel. 2009. Fishery-induced demographic changes in thetiming o spawning: Consequences orreproductive success. Fish and Fisheries10:283-304.

Zebdi, A., and J.S. Collie. 1995. Eect oclimate on herring (Clupea pallasi) popula-tion dynamics in the northeast PacicOcean. In: R.J. Beamish (ed.), Climatechange and northern sh populations. pp.277-290. Canadian Special PublicationFisheries and Aquatic Sciences 121.

Zwolinski, J.P., and D.A. Demer. 2012. A coldoceanographic regime with high exploita-tion rates in the northeast Pacic orecastsa collapse o the sardine stock. Proceedingso the National Academy o Sciences USA109:4175-4180.

The Pew Environment Group is theconservation arm o The Pew CharitableTrusts, a non-governmental organizationheadquartered in the United States thatapplies a rigorous, analytical approach toimproving public policy, inorming thepublic, and stimulating civic lie.

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Cover photo: Two shermen transer

anchovies, Engraulis mordax, rom acommercial shing boat hold to a live baitstorage pen, San Francisco Bay, Caliornia.Abner Kingman/GettyIllustrations: Steve RavenscratMaps: Adapted rom maps byGreenIno NetworkDesign: Imaginary Oce

the state of the science - forage fish in the california current

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