MFR PAPER 1353

B,lue Crab Larval Culture:Methods and Management

MARK R, MILLIKIN

ABSTRACT-Larval culture methods of the blue crab, Callinectes sapid us , andits associated food organisms are described in order to provide a guide for rearinglarvae for experimental and commercial purposes, Environmental parameters andadvantages of controlled rearing of blue crab larvae are discussed. Information onoptimal water quality parameters appears to be further developed than that fornutritional requirements of the individual larval stages. Metamorphosis and survivalof various blue crab larval stages fed several live food organisms are describedwith additional discussion of the culture of each food organism.

Mark R. Millikin is with the Charles­ton Laboratory, Southeast FisheriesCenter, National Marine FisheriesService, NOAA, P,O. Box 12607,Charleston, SC 29412. This paper isContribution No. 78-51 C from theCharleston Laboratory, SoutheastFisheries Center.

INTRODUCTIONThe reasons for annual fluctuations

in commercial blue crab landings fromthe"mid Atlantic. south Atlantic, andGulf Coast areas include: I) Bad yearClasses due to low hatchings from theprevious year, 2) natural catastrophes,3) overharvest in previous years, 4)lack of eelgrass or other protective veg­etation to provide refuge for soft crabsand smaller juveniles, and 5) pollutionofestuarine areas where juveniles feed.

Closed system larval rearing offersan alternative with increased controlover environmental parameters. Someadvantages of Closed system rearingare: I) No natural catastrophes, 2) nopesticides and other harmful chemicals,3) no predation, and 4) no cannibalismwhen individuals are reared separately.The importance of the blue crab to theseafood industry warrants serious con­sideration of the methods described inthis review as a tool of management tosupplement fluctuating natural popula-

10

tions. Any experimental work in bluecrab larval culture would also benefitfrom the following discussion.

METHODS

Survival in Natural VSArtificial Systems

The size of a normal egg mass froman ovigerous female has been estimatedat 1.75/<.106 -2 x 106 eggs by Churchill(1921) and 2>'106 eggs by Davis( 1965) and Warner ( 1976). Survival tothe mature adult under natural condi­tions has been estimated to be one out ofevery 2 million eggs produced (Warner,1976). Under laboratory rearing condi­tions, Sulkin et al. (1976) reported22.5-30 percent survival to themegalops stage. Costlow l has observed

I John D. Costlow. Duke University Marine Lab­oratory. Pivers Island, Beaufort, NC 28516.Pers. commun.

survival, under carefully controlledconditions, to the first crab stage rang­ing from 0 to 40 percent. The rate ofsurvival of the blue crab increasesdramatically under laboratory condi­tions after reaching the first crab stage.Unpubl ished resul ts from our laborato­ry with crabs raised from the first stageto juveniles (ranging from 3 to 7 cm inwidth) indicated 80 percent survival ina group of 400 individuals maintainedin compartmented plastic boxes sus­pended in glass aquaria containing ar­tificial seawater. Since environmentalvariables such as temperature, salinity,and dissolved oxygen have beendefi ned for the successful controlledculture of blue crab larvae, a better un­derstanding of their nutritional re­quirements and feeding behavior wouldappear to be a major concern in anyeffort to increase larval survival.

Mating and Spawning

Female blue crabs mate only once in

Marine Fisheries Review

their lifetime. Mating occurs after theirterminal molt in the soft crab stage.Enough sperm is received and stored inthe female's spermathecae for two andpossibly three spawning periods (Hard,1942).

Induced mating requires a knowl­edge of the molt cycle of the male andfemale. In the mating process, the maleshould have molted recently whileseparated from the female, so that thenext molt to occur will be that of thefemale. Otherwise, in the presence ofthe female the soft crab stage malewould be canni bal ized. However, thefemale is protected by the male hefore,during, and after her terminal molt.Van Engel (1958) describes the colora­tion of the abdomen of the immaturefemale crab as grayish- white and that ofthe adult female as blue-green. In thelast few days before the final molt of thefemale, the dark green of the inner,soft, mature abdomen shows throughthe translucent whiteness of the hard,outer, immature abdomen. Thischange, in addition to the red line stageon the border of the swimming paddleof the pre-molt female, should provideample warning that the terminal molt isapproaching. Abdominal appearance ofthe male can also be used to determineits status as a mature or immature indi­vidual. According to Van Engel( 1958), the abdomen of an immaturemale is tightly sealed on the ventralsurface of the shell, while on a matingmale the abdomen hangs free or is heldin place by a pair of snap fastener-liketubercles.

Induced mating and spawning underlaboratory conditions should include aholding tank with a muddy or gravelbottom to simulate the natural envi­ronment. Blue crabs and some othercrustaceans such as the freshwaterprawn, Macrobrachium rosenbergii,appear to abort egg masses frequentlyon smooth, unnatural bottoms such asglass, fiberglass, and Plexiglass2

. Aminimum of 2-3 months is requiredafter mating before ovulation occurs. In

2 Reference 10 trade names or commercial firmsdoes nOl imply endorsement by the National Ma­rine Fisheries Service, NOAA.

November /978

natural waters, such as the ChesapeakeBay, ovarian development may come toa halt during winter months as femalescease feeding activity below 10°C(Churchill, 1921). Dredged, overwin­tering females may be induced to renewovarian development and subsequentspawning after an acclimation period ofincreasing water temperatures underlaboratory conditions.

Egg Development In Vitro

An alternative to natural egg de­velopment and spawning has been pro­vided by Costlow and Bookhout(1960). This method provides severalessentials for viable egg development:I) Adequate aeration, 2) control offungi and protozoans in the egg mass,and 3) prevention of aborted egg mas­ses which females accomplish throughtearing with their walking legs. Eggsare cut from swimmerets previouslyplaced in 30%0 seawater with fine scis­sors and then further dissociated withglass needles into groups of 100-1,000.The eggs are then placed in plasticcompartmented boxes (9 cm2) contain­ing 20 ml of 30%0 freshly filtered sea­water treated with penicillin (200,000units/I). The boxes are placed on anEberbach variable speed shaker (I 10­120 rpm) and maintained at 22-25°C.Hatching of viable eggs was deter­mined at or near 100 percent in com­partments containing 100-1,000 eggs.According to Pyle and Cronin (1950),hatching occurs approximately 2 weeksafter egg extrusion onto the swim­merets. Churchill (1921) found hatch­ing time, after egg extlUsion, to varyslightly with different temperature re­gimes. At a temperature of 26. I °C(79°F) hatching of eggs required 14- 17days; at 29.4 °C (85 OF), hatching re­quired 12-15 days. Segregation of lim­ited size egg masses reduced the spreadof the fungal egg parasite, Lagenidiumcallinectes. Additionall y, by control­ling salinity, this method avoids prema­ture larval hatching due to lowsalinities, which can occur in naturalwaters (Van Engel, 1958).

The Egg Mass:Age and Disease

According to Bland and Amerson( 1974), the color of the egg mass can be

used in determining approximate age ofthe eggs, which can provide a reason­able indication as to how many days areleft before a holding apparatus for firststage zoeae should be made available.A yellow to orange color is characteris­tic of eggs that have been on the swim­merets 1-7 days. Brown to blacksponge color indicates 8- 15 days havepassed since egg extrusion onto theswimmerets.

Two particular diseases of the bluecrab egg masses more common thanothers are: I) Fungal disease caused byL. callinecfes and 2) parasitic infesta­tions by the nemertean, Carcinonemer­fes carcinophila. The fungal diseaseprimarily invades immature embryonicstages. Heavily infected eggs can berecognized by their smaller size andgreater opacity (Sindermann, 1974).The fungus develops in salinities from 5to 30%0, spreading rapidly onto theperipheral eggs while avoiding thecenter of the egg mass. Infected eggs donot hatch and zoeae hatched from eggspreviously uninfected may stiJl becomeinfected if left in medium containingfungus spores. Female crabs with in­fected egg masses should be removedfrom brood tanks immediately. Imma­ture C. carcinophila, living in the gilltissues of the gravid female, migrate tothe egg mass after extrusion onto theswimmerets. The worms become sexu­ally mature only in the egg mass. Aftermating, the female C. carcinophilawithdraws from its mucus tube, leavinglarge numbers of eggs within the bluecrab egg mass. Development and hatch­ing of nemertean eggs occur within 36hours. Some migrate back to the gillchambers of the adult female crab,while others swim freely from the hostto infest other crabs. However, thedamage caused from the nemerteanparasite is not as extensive as thatcaused from the fungal disease.

Characteristics and OptimalWater QualityParameters for ZoealSurvival and Development

Blue crabs normally go throughseven zoeal stages but have survived tothe megalops after only six zoeal stages(Sulkin el al., 1976) and even following

/I

a supernumerary t;ighth weal stage(Costlow and Bookhout, 1<159). Eachof the seven normal zo-:al stages hasmorphological changes described in de­tail by Costlow and Bookhout ( jY59).Zoeae are heliotropic and free­swimming but are classified asplanktonic due to a lack of control oftheir position in tidal and strong currentareas. In natural environments, eggsappear to successfully hatch in salini­ties of 23-30%0. Costlow and Bookhout(1959) and Sulkin and Epifanio (1975)reported that the optimal temperaturefor lOeal development is 25°C. Opti­mal salinity for lOeal developmentranges from 26%0 (Costlow andBookhout, 1959) to 300/00(Sulkin et al.,1976). Additionally, Sulkin et al.(1976) found synthetic seawater tocompare favorably to natural seawaterin terms of lOeal survi val as 50 larvae (5sets of 10) in natural water achieved22.5 percent survival through the mega­lops stage, whereas a comparablenumber of larvae in synthetic seawaterattained 30.0 percent survivaJ throughthe megalops sta~e. Larvae rarely com­pleted their first molt to second stagelOeae in salinities lower than 20°/00 ortemperatures below 20 0 e (Costlow andBookhout, 1959). Mortality of bluecrab larvae was highest duri ng the firstt\yO meal stages (Costlow and Book­hout, 1959). A comparison of envi­ronmental parameters used by differentinvestigal\)rs is summarized in Table I.

Total time for lOcal developmentranged from 31 to 49 days for the sevenstages (Costlow and Bookhout, 1959)compared with an average duration of35.7 days when only six lOeal stagesoccurred (Sulkin et aI., 1976).

Blue Crab Larval Feeding

Little if any qualitative or quantita­tive research has been conducted onnutritional requirements of the lOealstages of the blue crab. With regard tonatural foods, several plant and animalorganisms have been evaluated for theirability to support survival and growthof larvae to the megalops stage.

According to Costlow and Bookhout( 1959), unicellular algae when fed as asole food source did not provide enoughnutrition for successful molting from

J2

the first to second zoeal stage, althoughingestion by the zoeae was ubserved forup to 10-13 days. apparently resultingin a someW'lat prolonged survival time.Rust and Carlson (I <160) obs-:rvl:d noarparent utilization of the followingphytoplankton by blue crab zoeae:GYllll1odiniw/I. Amphidiniul1I, Chlam­ydomonas. Plwnnunus, Isochrysis,Monochrysis. Prorocf'ntrul11 , .Vitzs­chia, ('arteria, Chlorella, or Dunali­dla. Possibly onl: reason that algalspecies have failed to promote growthof lOeae is that algal diets arc totall)devoid of animal sterols, which appearessential in the diet of the blue crab.Whitney ( 1970) found that the blue crabis incapable of de novo synthesis ofcholesterol from eithel acetatc- 14 C ormevalonate- 14C. Based on her studies,Whitney theorized that rapid moltingand tissue growth in the larval stagesrequire large amounts of sterols for newsubcellular membrane formation.

Sulk in (1975) has reared weae fromthe first stage to the megalops with asurvival rate of 17 percent on a diet ofgastrulae and trochophores from thepolychaete, Hn/mides dianthus. In thesame study, rotifer-fed zoeae did notreach the mega lops ~lage, althoughsome survival through the eighth wealstage was observed. Mortalities inweal stag,'-:~; III, IV, and VI! werl: sig­nificantly lower in polychaete-fed crab

Table 1.-Environmental parameters used tor zoealculture.

Cosllowand Sulkin andItem Bookhoul (' 959) Epitanio (1975)

Temperature 25'C 25'C

Salinity 26%0 30%0

Photoperiod t 2 lightl12 dark 14 lighU'O dark

Table 2.-Maximum sizes of several live food organismsoffered to blue crab zoeae'.

SizeOrganism (!-'m)

Rotiter (Brachlonus plicalilis) 45-80

Sea urchin egg (Arbacea puncrulara) 72-75

Sea urchin egg (Lyrechinus vanegarus) '10

Recently hatched nauplius(Artemia salina) 250

'From Sulkin and Eplfanio (1975).

Jarvae than in those fed the rotifer diet.Brine shrimp nauplii, Anemia salina,alone did not sustain growth from thefirst to sc:cond zoeal stages. and mortal­ity occurred unless either ratifer or seaurchin egg supplements were provided(Sulkin, 1975). Costlow (pers. com­mun., footnote I) has also recom­mended using sea urchin eggs (Arbaceasp.) along with freshly hatched Anemianaupl ii (less than or equal 10 12 hoursold) for the feeding of weal stages I andII. Freshly hatched Anemia naupliimay be used as the sok food organismfor lOeal stages IIl- VJI. Thl: size offeed organisms appears to determinethe blue crab wea's ability to captureprey (Sulkin and Epifanio, 1975). Thiswould expJain the apparent lack of sur­vival of first and second stage blue crabzoeae when brine shrimp nauplii areoffered as the sole food.

Table 2 Iists the sizes of several Ii vefood organisms fed to blue crab zoeaeby Sulkin and Epifanio (1975). Theseinvestigators concluded that food or­ganisms of 110 J-U11 or less are optimalfor the first and second lOeal stages.

Sulkin and Epifanio (1975) made acomparison between groups of stage Iand II zoeae fed either sea urchin gas­trulae or a rotifer diet. After 14 days,survival in the sea urchin gastrulae-fedgroup equalled only 5 percent as com­pared with 50 percent among theroti fer-fed animals.

Sulkin (1975) has suggested that thehigh degree of success in rearing zoeaethrough the later stages with brineshrimp nauplii may be due to the highlipid content of the nauplii, which infact may be required as larvalmetamorphosis approaches. Sea urchinlarvae (derived from isolecithal eggs)are inferior to polychaete and brineshrimp larvae (derived from telolecithaland centrolecithal eggs) in supportinglarval metamorphosis of the blue crabto the megalops stage. This may indi­cate that the type of embryological de­velopment determines the nutritionalvalue of the particular food organism asa zoeal food source for the later stagezoeae (Sulkin, 1975). Total lipid perunit dry weight as determined by Sulkin(1975) for several food organisms is asfollows: mixed rotifers-8 percent,

Marine Fisheries Reviell'

Zoeae fed Artemia salina fromGreat Salt Lake. Utah 31 24

'From Bookhout and Costlow (1970).

Culture of Feed Organismsfor Blue Crab Larvae

Environmental parameters, algalspecies, and feeding rates, which pro­vide optimal survival and developmentfor the culture of the rotifer, Brach­ionus plicatilis, and the brine shrimp,A. salina, will be described in order toprovide ample food for blue crab larvaein a larval culture operation.

The rotifer, B. plicatilis. is describedas a mixohaline species because of its

to 400 f.Ull and sphere-shaped zoeaerange from 200 to 300 /Lm, a screenwith a 100/Lm mesh size is recom­mended for separation of the larval col­lection chamber from the biologicalfilter section to prohibit flow of larvaepast the larval collection chamber. As aresult of using a smaller screen meshsize than that recommended for fresh­water prawn, differences in head lossmay be reduced through decreased flowrate or increase in surface area of thescreen.

Serfting et al. (1974) designed a re­circulating culture system (Figs. 2, 3)for larvae of the American lobster,Homarus Gmericanus, which is a mod­ified version of an earlier system de­veloped by Hughes et al. (1974). Itwould appear that Serfling 's sytstem of­fers a practical holding system ap­proach for the mass rearing of blue crablarvae even though the first two zoealstages would have to be separated fi'omthe last fi ve zoeal stages due to differentfood organisms being offered (i.e.,rotifers for zoea I and II and brineshrimp nauplii for zoea III to YI£).Either a duplicate system or com­partmented boxes would be required forthe first two zoeal stages. The systemdescrihed by Serfling et aJ. (1974) has a10 liter/minute flow rate for larval dis­persal and provides primary filtrationthrough a graded sand (No. 12 silica)and crushed oyster shell filter bed. Sec­ondary filtration includes a charcoaland fiber filter used to remove chemicalcontamination and residual particulatewastes. Serfling et al. (1974) also dis­cusses the use of heating elements aswell as occasional ultraviolet steriliza­tion of the water, together with antibi­otics.

benthic as well as planktonic behavior,allowing for better utilization of foodthroughout the water column than thestrictly planktonic zaeal stages. Chur­chill (1921) reported average sizes ofthe megaJops and the first crab as O. 102cm and 0.254 em, respectively. Exter­nal anatomy of the megalops stage isdescribed in detail by Costlow andBookhout ( 1959).

Costlow (1967) fed newly hatchedArtemia nauplii to blue crab mega/opsand monitored the effects of varioussalinity-temperature combinations onsurvival and rate of development to thefirst crab stage. The optimal salinity­temperature combination was deter­mined to be 25°C and 30%oas 100 per­cent survival was achieved with anaverage of 8.4 days (6-12 days) re­quired for metamorphosis to the firstcrab. Sulkin (1975) found that nearlyall megalops successfully metamor­phosed to the first crab stage when fedAnemia naupl ii and occasional piecesof fish. However, no megalops reachedthe first crab stage when fed exclusivelyon the polychaete, H. dianthus. Due tothe increased mobility and larger clawsize, the mega lops of the blue crab isable to prey on Artemia nauplii of alarger size range than may be eaten bythe zoeae. However, adult Anemiashould not be fed until the blue crabreaches the first crab stage (Costlow,pel's comm., footnote I).

Holding Tanks for MassCulture of Blue Crab Larvae

A combination larval hatching­collection chamber designed by Smithand Hopkins (1977) for separatingnewly hatched freshwater prawn, M.rusenbergii, from egg-bearing femalesappears suitable for use with the bluecrab (Fig. I). This system util izes airlift pumps that discharge 7.6 liters/minute of water into the hatchingchamber, providing a current whichcarries larvae through a nylon screen(0.6 cm mesh size) into the collectionchamber. Light above the collectionchamber causes positive phototactic re­sponse of crustacean larvae to concen­trate most individuals near the surfacefor easy retrieval. Because outstretchedstage J blue crab zoeae range from 300

3450

Table 3.-Survival of blue crab larvae fed brine shrimpobtained from two different geographic regions'.

Percent Percentmoiled moiled

into intonormal first crab

megalops slage

large rotifers-9 percent, thepolychaete, H. diunrhus-20 percent,and brine shrimp nauplii-30 percent.

Careful selection of potential foodorganisms, based not only on their abil­ity to promote maximal survival andgrowth, but also on their freedom fromorganic and inorganic contaminants aswell as biological vectors, is an impor­tant consideration for the larval cul­turist. Bookhout and Costlow (1970)demonstrated the importance of thegeographic region from which brineshrimp originate in feeding studies withnewly hatched blue crab weae fedeither San Francisco Bay or Great SaltLake brine shrimp. Upon analysis forDDT in brine shrimp from the GreatSalt Lake, a total of 7,050 parts perbi Ilion (ppb) were detected, whereasSan Francisco Bay brine shrimp con­tained approximately 2,300 ppb. Al­though the length of time required fordevelopment to the megalops stage wassimilar for both brine shrimp-fedgroups (about 46 days), there weresome indications (Table 3) that thehigher pesticide levels detected in GreatSalt Lake brine shrimp may have pro­duced greater mortality. Despite thecurrent lack of technical knowledge onthe specific nutritional requirements ofthe blue crab zoeae, with present rear­ing methods and associated feedingtechniques, the larval culturist can bereasonably assured of achieving sig­nificantly better survival through thefirst seven zoeal stages than that knownto occur in nature.

The finaJ zoeal stage of the blue crabmetamorphoses into the megalops,which precedes the first crab stage orinstal' of the juvenile period of de­velopment. The mega lops exhibits

Zoeae led Artemia salina fromSan Francisco, Calif.

Region

November /978 13

AiR L1NE---------\\ 6 LIGHT COVER

AIR- LIFT WATER PUMP-----jl-Ii

PLAS TIC PARTITIONS --,,*~~~~~M--------1I

GRAVEL FILTER BED-----j~

nLTER BED SUf'PORT-- ""'"

BIOLOGICAL FlLTER SECTION ....J LARVAE HATCHING CHAMBER

AIR LINE

WATER EXIT (fine mesh screening) ---------;f~~;t;;!@

LARVAE AND WATER ENTRY(iorge mesh screening)-J,--fl±ati±at1i~tii~±±~~

LARVAE COLLECTION CHAMBER

Figure I .. --Longitudinal and frontal view of hatching-collection chamber (Smith and Hopkins, 1977)

RECI RCU LATING CULTURE SYSTE M

Figure 2.-Front. cross-seclionalview of Ihe recirculaling cullure ~yslem. showing the HughesCullure Tank and the Circulator design and the primary and secondary fillralion systems.Illustration is from Serf1ing et al. (1974), courtesy of Elsevier Scientific Publishing Company,Amsterdam. The Netherland~.

LARVAL m:;'1CULTURE : :, ,

TANKS : '

~! i~,nla,e _ ~ ),

(fronl view)

HEAT

EXCHANGER

&

CHARCOAL

FIllER

PUMPINGSYSTEM

BATTERY&

RELAY

tolerance of a wide salinity range (0.5­40%0) without any apparent adverse ef­fects (Theilacker and McMaster,1971). This species is casily obtainedand cultured as a result of its wide toler­ance to variable environmental para­meters. To maintain an optimal envi­ronment for both rotifer culture and itsalgal food source. a water salillity of25%0 and a temperature of 21 c·25°Cwere established by Theilacker andMcMaster (197 I). These conditionswere based on observations that the rc­productive rate of B. plicalilis wassimilar in either 25 or 30%0 :-,eawaterand the fact that growth of the algalfood source, Duna/ie/fa sp., appearedoptimal at a salinity of 25%0. Based onexperimentation with four algal genera,Duna/iel/a, Nanl1och/oris, Exuviella,and Monochrysis, Theilacker andMcMaster (1971) concluded that the

/4 Marine Fisheries Review

RECI RCU LATING CULTURE SYSTEM

(end view)

Figure :I.-End. cross-sectional view of the recirculating culture system. show­ing the secondary filtration and back-up power systems. Illustration is fromSerfling et al. (1974), courtesy of Elsevier Scientific Publishing Company.Amsterdam. The Netherlands.

unicellular flagellate, Dunaliel/a sp.,was the most practical choice. Thisspecies did not require vitamins or soilextract in the culture medium. For cul­ture of Dunulie//u, ultraviolet-treated24%oseawater was filtered through twoCuno Aqua-pure filters (pore size =5J.Lm), a large capacity millipore car­tridge pre-filter and filter (poresize =0.45 j.Lffi), and reirradiated withultraviolet light. Sixteen liters ofmedium maintained at a temperature of24 0::,::: 1°C in 20-liter carboys were bub­bled with 5 percent carbon dioxide andagitated with a magnetic stirrer underconstant illumination at a light intensityof between 500 and 700 footcandles.Cell numbers were found to increasefrom 3.4X103 to 3x\0') cells/ml in 9days. At peak growth, 25 percent of thealgal culture is removed daily and re­placed with fresh media for 10additionaidays. ror mass rotifer production,fiberglass tanks were filled to a depth of13 cm (464 liter volume) and inoculatedwith 32 liters of Dunaliel/a culture to

LARVALCULTURE -­

TANK

CHECK VALVE -

RESERVOIRTANK WITH ­

~ILTEA BED

yield a final concentration 2 x I0:;cells/ml. When Duna/iel/a concentra­tions reached I X IO f

; cells/ml (2-4days), the fi berglass tanks were chargedwith approximately 2 x 10~ rotifers.The tanks were then aerated under con­stant illumination at an intensity of140-170 footcandles. This proceduresupported a production of 2.5 x 106

rotifers/day within a 4 or 5 day period.The size of B. plicati/is ranged from 99to 281 J.Lm. Average rotifer weightequalled 0.16 j.Lg with an energy con­tent of an individual animal determinedto be 8 x 10 -. calories. An averagecaloric content was estimated at5,335 ± 139 cal/g of ash-free dryweight. Rotifer concentrations as highas 200/ml did not inhibit reproduction.Separation of rotifers from the algalmaterials was accomplished with theaid of a submersible pump and plastictube covered at one end with 64J.Lmmesh netting (Theilacker and McMas­ter, 1971).

Techniques for producing newly

---

t

hatched brine shrimp nauplii have beenthoroughly described by Sorgcloos andPersoone (1975). Hatching of cysts inseawater was found to require a salinitybetween 5 and 70%0. However, Boul­ton and Huggins (1977) comparedhatching rates in salinities of approxi­mately 0, 17.5, 35, 52.5, and 70%0seawater after hydration for 6 hours aswell as after subsequent 3-hour inter­vals up to 30 hours. No free swimmingnauplii were observed in 50 percent di­luted seawater after 30 hours of hydra­tion. Highest percentage hatching oc­CUlTed in full-strength seawater after 27hours (63 ± I I percent) and 30 hours(69 ±9 percent). Hatching rate in highersalinities was greater with each addi­tional 3-hour interval from initial hy­dration but remained lower than thatachieved in full-strength seawater. For"Californian cysts," illumination for10 minutes at an intensity of approxi­mately 185 footcandles (2,000 lux) in amedium containing at least 3 ppm dis­solved oxygen is sufficient for success­ful hatching (Sorgeloos and Persoone,1975). These same authors have re­ported an optimal temperature to equalapproximatley 30°C. Foaming (proteinbubble formation), which is caused bydecomposed byproducts of dead Ar­femia, can be minimized by using a fewdrops of nontoxic silicone antifoamer.A cylindrical separator box constructedby Sorgeloos and Persoone (1975)capital izes on the positive phototacticbehavior of newly hatched nauplii andis an improvement over rectangular bot­tom containers used in the past. Thisseparator avoids accumulation of cystsand newly hatched nauplii in corners,which causes low hatching and poorsurvi val rates.

Culture of brine shrimp beyond thenewly hatched stage is recommended inorder to feed the megalops stage andearly instars of the juvenile period. Thephytoflagellate, Dunaliella viridis, is asatisfactory feed organism for newlyhatched nauplii. Funnel-shaped bot­toms for algal culture vessels (Fig. 4, 5)eliminate sedimentation and permit cir­culation of nutrients (Persoone andSorgeloos. 1975). Some investigatorshave used a supplemental source ofC02 for algal culture, whereas others,

November /978 /5

Figure 1. -Algal culturing tube, 100m! (Persoone and Sorgeloas, 1975).

such as Persoone and Sorgeloos ( 1975),insist that in high density cultures, opti­cal density of the culture is more limit­ing than insufficient amounts of C02.The use of axenic cultures for algal pro­duction is not generally encouraged dueto: I) Low amount of bacteria presentduring the exponential growth phase ofthe algal colony, and 2) the high ex­pense and cumbersome work involvedin keeping a bacteria-free culture. Per­soone and Sorgeloos ( 1975) suggestedthe following stock solution for cultureof Dunaliella sp.:

Extensive research by many inves­tigators has provided useful informa­tion on the culture of feed organisms foruse in blue crab larval culture. Eachfood organism has its own environmen­tal parameters for optimal survival andgrowth. Often, this dictates a com­promise of environmental parametersbetween any two adjacent organisms inthe food chain, e.g., Dunaliella andAnemia or Anemia and Callinecles. Asmore knowledge of nutritiorutl re­quirements is gained, formulated feedscould become practical for eCOl,omic

for several phytoplankton species fed tobrine shrimp larvae and found bettergrowth in larvae fed high protein-lipidspecies, such as D. viridis and Chla­mydomonas sphagnicolo, as opposed tohigh carbohydrate species, such asNitzschia closterium. Paffenhofer( 1967) determined the average contentof newly hatched Anemia nauplii to be5,953 cal/g ash-free dry weight.

Use of dry powder forms of a feedorganism as a substitute for live cul­tures minimizes the number of livinglinks necessary to culture the desiredspecies. Person - LeRuyet (1976) hasdeveloped a technique for intensiverearing of brine shrimp larvae using theblue-green alga, Spirulina maxima, indry powder form. On a weekly basis,productions of 75 g of dry matter ofbrine shrimp from a 450-liter tank wereattained. Table 4 summarizes optimalconcentrations of larvae and the amountof dry powder required. The averagesize of an ind ividual larva as well asoptimal concentration compares favor­ably with previous results attained bySorgeloos (1973) using live food forArtemia larvae.

SUMMARY

0.278 g3.0 g

30.0 g0.47 g

50.0 gI liter

FeS04 '7H20NaH2P04 ·2H20NaN03MnCI2 AH20GlycocolDistilled water

In high density culture experimentswith brine shrimp nauplii, Sorgeloos( I973) achieved concentrations of be­tween I and 3 nauplii/ml at a tempera­ture of 28°C as follows: I) 2,000 in­dividuals in I-liter containers (2nauplii/ml); 2) 25,000 individuals in10-1 iter containers (2.5 naupl ii/ml); and3) 50,000 individuals in 30-1iter con­tainers (1.6 nauplii/ml). Each naupliusrequired 50,000 Dunaliella cells twicedaily during the first 4 days of cultureand 100,000 Dunaliella cells duringdays 5 through 8. One minute of airbubbling every half hour by an airpump, which is switched on by a timingclock, provides adequate aeration andrecirculation of Dunaliella cells. Addi­tionally, Sorgeloos (1973) recom­mends growing Anemia larvae in com­plete darkness to provide a fastergrowth rate. Sick (1976) monitoredcarbohydrate, lipid, and protein values

jAIR INLET

o

o

*' AIROUTlET

1 tilER

AIR

Table 4.-Growth of larval Arlemis ssllna as influenced by algal food concent­ration and larval density'.

600 1 (after 2 days)

AmI. (mg) of Brine shrimppowder2 larva sizeollered X(mm)

13-14

Adjusledlarval con­

cenlration/ml

2 (afler 4 days)1,800

No. oflarvae

10.000

10,000

0-2

3-4

Days

'From Person - LeRuyet (1976).2Blue-green alga, Spirulina maxima, in dry powder form.

Figure 5.-Glass serum bOllle usedfar culturing algae. (Persoone andSorgeloas, 1975).

5-6 10.000 4.300 3.75 (afler 6 days) 2

/6 Marine Fisheries Review

purposes as well as easing the amountof work associated in culturing foodorganisms required for blue crab lar­vae.

Presently, it appears that brineshrimp nauplii, in combination with seaurchin eggs or rot ifers, may be fed suc­cessfully to the first two zoeal stages,while brine shrimp nauplii appear to bethe best available food organism for thesubsequent zoeal stages (III- VII). Themegalops stage requires brine shrimpnauplii in order to metamorphose intothe first crab stage under laboratoryconditions.

Despite extensive work by severalinvestigators, survival of blue crab lar­vae under laboratory conditions re­mains below that attainable with othercrabs (i. e., the mud crab, Rhithro­panopeus harrisi, and the stone crab,Menippe mercenaria). Although highlyvariable, Costlow (pers. commun.,footnote I) has indicated a maximumsurvival rate to the first crab stage ofapproximately 40 percent.

Studies monitoring the nutritionalrequirements of juvenile crabs havebeen highly successful when usinghatchery-raised individuals as opposedto individuals captured from naturalwaters (Biddle, pers. commun., foot­note 3). Juveniles obtained from naturalwaters frequently succumbed to diseaseafter transfer to laboratory holding sys­tems, whereas hatchery-raised crabsdid not exhibit similar problems.

ACKNOWLEDGMENTS

I thank Garfield Biddle, Paul Bau­ersfeld, and Harry Seagran of theCharleston Laboratory, NationalMarine Fisheries Service, NOAA, fortheir critical review of the originalmanuscript and John Costlow, Jr., ofthe Duke University Marine Labora­tory, who gave valuable insight intolarval culture methods. I also thank thefollowing authors/publishers for per-

mission to reproduce their originalfigures: Guido Persoone and PatrickSorgeloos of the State University ofGhent, Ghent (Belgium); Frank Taylorand Theodore Smith of the Marine Re­sources Research Institute of SouthCarolina; Steven Serfting of SolarAquafarms, Inc.; and the Elsevier Sci­entific Publishing Company, Amster­dam.

LITERATURE CITEDBland. C. E., and H. V. Amerson. 1974. Occur­

rence and distribution in North Carolina watersof Lagel/idium cal/il/eetes Couch. a fungalparasite of blue crab ova. Chesapeake Sci.15:232-235.

Bookhout, C. G., and J. D. Costlow, Jr. 1970.Nutritional effects of Artemia from differentlocations on larval development of crabs. Hel­goL Wiss. Meeresuters 20:435-442.

Boulton, A. P., and A. K. Huggins. 1977.Biochemical changes occurring during mor­phogenesis of the brine shrimp Artemia salinaand the effect of alterations in salinity. CompoBiochem. Physiol. 57A:17-22.

Churchill, E. P., Jr. 1921. Life history of the bluecrab. Bull. U.S. Bur. Fish. 36:95-128.

Costlow. J. D., Jr. 1967. The effect of salinityand temperature on survival and metamor­phosis of megalops of the blue crab Callinectessapidus. Helgol. Wiss. Meeresunters 15:84­97.

____ and C. G. Bookhout. 1959. The lar­val development of CallineCles sapidus Rath­bun reared in the laboratory. BioI. Bull.(Woods Hole) 116:373-396.

____and . 1960. A method fordeveloping Brachyuran eggs in vitro. Limnol.Oceanogr. 5:212-215.

Davis, C. C. 1965. A study of the hatching pro­cess in aquatic invertebrates: XX. The bluecrab, Cal/if/eetes sapidus, Rathbun, XXI. Thenemertean, Careinol/emertes carcil/ophila(Kolliker). Chesapeake Sci. 6:201-208.

Hard, W. L. 1942. Ovarian growth and ovulationin the mature blue crab, Cal/ineetes sapidusRathbun. Chesapeake BioI. Lab., Publ. 46,17p.

Hughes. J. T., R. A. Shleser, and G. Tchobano­glous. 1974. A rearing tank for lobster larvaeand other aquatic species. Prog. Fish-Cult.36: 129-133.

Paffenhofer, G.-A. 1967. Caloric content of lar­vae of the brine shrimp Artemia salina. Helgol.Wiss. Meeresunters 16: 130-135.

Person - LeRuyet, J. 1976. Rearing of Artemiasalina (Branchiopoda) larvae on inert food:Spirulina maxima (Cyanophycea) (In French,Engl. summ.) Aquaculture 8:157-167.

Persoone. G., and P. Sorgeloos. 1975.

Technological improvements for the cultiva­tion of invertebrates as food for fishes andcrustaceans. I. Devices and methods. Aquacul­ture 6:275-289.

Pyle, R., and E. Cronin. 1950. The generalanatomy of the blue crab, Cal/ineetes sapidusRathbun. Chesapeake BioI. Lab., Pub I. 87,40p.

Rust,J. D., and F. Carlson. 1960. Someobserva­tions on rearing blue crab larvae. ChesapeakeSci. I: 196-197.

Serfting, S. A., J. C. Van Olst, and R. F. Ford.1974. A recirculating culture system for larvaeof the American lobster. Homarus ameri­COl/liS. Aquaculture 3:303-309.

Sick, L. V. 1976. Nutritional effect of fivespecies of marine algae on the growth. de­velopment, and survival of the brine shrimpArtemia salif/a. Mar. BioI. (Berl.) 35:69-78.

Sindermann, C. J. 1974. Diagnosis and control ofmariculture diseases in the United States. U.S.Dep. Commer., NOAA, Natl. Mar. Fish.Serv., Middle Atl. Coastal Fish. Cenl., High­lands, N.J., Tech. Ser. Rep. 2, 306 p.

Smith, T. I. J., and J. S. Hopkins. 1977. Tankdesigned for hatching and collecting larvae ofthe giant Malaysian prawn, Macrobrachiumrosenbergii. Prog. Fish-Cult. 39: 182-183.

Sorgeloos, P. 1973. High density culturing of thebrine shrimp, Artemia salil/a L. Aquaculture1:385-391.

____ and G. Persoone. 1975. Technologi­cal improvements for the cultivation of inver­tebrates as food for fishes and crustaceans. lJ.Hatching and culturing of the brine shrimp,Artemia salina L. Aquaculture 6:303-317.

Sulkin, S. D. 1975. The significance of die! in thegrowth and development of larvae of the bluecrab, Cal/inectes sapidus Rathbun, underlaboratory conditions. J. Exp. Mar. BioI. Ecol.20:119-135.

____, E. S. Branscomb, and R. E. Miller.1976. Induced winter spawning and culture oflarvae of the blue crab, Callinectes sapidusRathbun. Aquaculture 8: 103-113.

____ and C. E. Epifanio. 1975. Compari­son of rolifers and other diets for rearing earlylarvae of the blue crab, Cal/inectes sapidusRathbun. Estuarine Coastal Mar. Sci. 3: 109­113.

Theilacker, G. H., and M. F. McMaster. 1971.Mass culture of the rotifer, Brachiof/us plica­tilis and its evaluation as a food for larvalanchovies. Mar. BioI. (Berl.) 10: 183-188.

Van Engel, W. A. 1958. The blue crab and itsfishery in Chesapeake Bay Part I. - Reproduc­tion, early development, growth, and migra­tion. Commer. Fish. Rev. 20(6):6-17.

Warner, W. W. 1976. Beautiful swimmers. LittleBrown & Co., Boston, 304 p.

Whitney, J. O'c. 1970. Absence of sterol biosyn­thesis in the blue crab Cal/ineetes sapidusRathbun and in the barnacle Balanus nubilusDarwin. J. Exp. Mar. BioI. Ecol. 4:229-237.

November /978

MFR Paper 1353. From Marine Fisheries Review, Vot. 40, No. II, November1978. Copies of this paper, in limited numbers, are available from 0822, UserServices Branch, Environmental Science Information Center, NOAA, Rockville,MD 20852. Copies of Marine Fisheries Review are available from the Superin­tendent of Documents, U.S. Government Printing Office, Washington, DC20402 for $1. 10 each.

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