Development of the Pelagic Red Crab (Galatheidae, Pleuroncodes Planipes) Fishery in the Eastern Pacific Ocean

MFR PAPER 1091

Improved handling and development of new uses will be the key to the red crab fishery.

Development of the Pelagic Red Crab (Galatheidae, Pleuroncodes planipes) Fishery in the s) Eastern Pacific Ocean

SUSU MU KATO

INTRODUCTION Recent fishing trends demonstrate Id that the oceans may not contai n an inexhaustible supply of fishes. Many ar of the major fisheries of the world have reached their peaks and several have declined because of decreasing populations. Thus, more and more the fishing nations have turned to with the aid of the National Marine Figure 1.- The pelagiC red crab, Pleufoncodes planipes. OYerall length is about 3.5 inches. previously unutilized resources, and Fisheries Service (NMFS) and the (From Boyd, 1962.) to aquaculture, to satisfy an ever in­ Mexican Government, have started creasing demand for marine products. commercial utilization of the pelagic li ance of their color ma) depend In Many species of fish and other ma­ red crab. This paper summarizes the part on ambient li ght conditions. rine organisms remain unutilized be­ biological information on red crabs LIFE HISTORY cause knowledge is lacking about a nd the evolution of the fishery. their distribution and abundance, or Each female may have t\\o and owing to a lack of technologica l ca­ sometimes three broods of egg In pability to harvest and process them o ne season. Females may carr) up economically. As new harvesti ng and DESCRIPTION to 3,650 eggs which hatch after abl'ut processing methods develop, concur­ The pelagic red crab. Plellrollcodes 2week.s(8oyd,1962). rent with accumulation of knowledge plallipes Stimpson (Fig. I), is a mem­ I n the laboratory . crabs have passed about new resources it becomes pos­ ber of the crustacean family Gala­ through five larval stages in frum sible to utilize previously unused spe­ theidae, a group of small, lobster-like 2 to 4 months (BoJd, 19(0), th~ cies. Thus. for example, the Japanese crabs. Boyd (1962) points out Stimp­ length of time depending primanh and Russians have started fisheries son's humorous intent in deriving the on the temperature of the culture for the small shrimp-like euphausiid name Plellrollcodes plallipes. which medium . The young crab kad .. ("krill") which is abundant in Antarc­ translates to "bulgy-sided crab with planktonic life for about a ) edr lH0~d tic waters (Lyubimova, Naumov, and fiat feet." Galatheids typically have 1962). Sometime during thclr econd Lagunov. 1973). abdomens and tai l fans well-adapted Year, crabs become reprOduClI\\. \ Another large crustacean resource for swimming, and their long first ;"ature a nd spend lime on the bOllO n is the pelagic red crab ( Plellrollcodes pair of legs is armed with pincers as well as in the plank.ton B) thl plallipes) found off the western coast (chelipeds) (Schmitt, Inl)' Rows of time the crabs are dbl)ut l) 6 Ireh of Mexico, especially near Baja Cali­ hair-like setae are located on the long' (8oyd and John,,)n, 1'16, B\ fornia. (This species should not be front and hind margins of the walk­ the end of the econJ) Cdr the crab 'zc of confused with the deep-sea red crab, ing legs . Their probable function is become strictlv benthiC ..It a Geryoll qllillqlledens, of the Atlantic discussed later. about 1.02 Inches (80)J, 19A21 Principal -.pa\\nlng ground for coast.) Recently .American fishermen. Adult red crabs are about 3.5 to 5 n<.:dr inches long, with the tail and cheli­ red crab probabl) are In hore Susumu Kato is with the South­ peds extended (Fi g. 2), A pou nd of west Fisheries Center's Tibur­ I The 0 6-m~h c~r.lpacC :cn!!th n c on Laboratory, National Ma­ red crabs includes about 100-1:0 from the bC! e of the large pme.lI the r "1t adult individuals. Their color ranges of the he.ld to the p ler.or mugu' f tt­ rine Fisheries Service, NOAA, carapC!ce I u,ed.l' the l.l'ldard r e ure Tiburon , CA 94920. from pale orange to bright red: bril- rnenllhroughllullhl paper

1 Figure 2.-Adult red crab • . The primary breeding sea~o n for red crabs appear~ to be from J anuary through March (B oyd a nd J o hn ~on, 1963). but I have ~een berned females In late October. and young larvae have been found dUring o ther month~. In the laboratory, the egg-bearing sea­ son was ovember through April. en with a peal<. In rebruary (Boyd. 1962). ~ > Larvae of most alathelds a re Z o plan\..tonlc (carned paSSively by cur­ > II renhl. and adults are usually benthiC o (live on the bottom) Adults of MUI11da en lin' liana , an Antarctic ~pecle~. how­ r e,er. occasionally swarm In mldwater ;; z or at the surface (Matthews. 1932). Red crabs are unique In that they

(') \pend a conSiderable part of their F,gure 3.-Dead crabs strewn auult life both on and off the bottom on the beach at Bahia Magda­ lena . anu may \.I.ell Interchange the'>e dif­ ferent life sty I~ as conditions dictate (BOyd. 1967) The term "pelagiC." usually referring to strong ~\.I. Immers. has been applied to reu crabs found off the bottom. but \.I.lth the under­ stanulng that currents pIa) a major role In their distribution and mo,e­

) ment'> rabs larger than about I Inch \ - '"'r- In carapace length. probably 2 years -'\.- olu . appear to be strictI) benthiC and " , .I Ii\e In ueeper \\ater of the continental - shelf (Ibid) BOyd (1967) found Igntficantl) higher catch rates of red crabs In plan\..ton haul at night than dUring the da) . H e attributed the dtfference to up\.l.aru migration from deeper \.I.ater at night and the re\erse during the day . rab~ caught at night \.I.ere generall) larger. as \.I.ere those caught at higher latitude~ . The habit of \.I.armlng at the sur­ face ma\..e red crabs con picuous to ocean tra\eler . The e \.I.arm~ are ap­ parentI) not associated with easonal (winter) breeding cycles (Bo) d. 1967). Windro\.l.s of c rabs a t th e surface ometimes stretch for mile h\..e a blood-red ri \ er. uch concentration occur more commonl) at ni g ht. but are also e \ide nt during the day (Boyd. 1962). I\la s mortalities occur when the pelagic red crabs a re carried to southern Baja California. especially Breeding al~o occur far offshore shore by winds. wa'es. and currents in the region of Bahia Magdalena (Longhurst and Seibert. 197 1), a nd (Fig. 3). (Boyd. 1960). Katsuo Ni hikawa. during certain years as far north as Escuela de Ciencias Marinas. En­ o uthe rn Califo rnia. Probably these FEEDING AND PREDATORS sen ada (pers. comm .), reported find­ crabs have difficulty returni ng to th e ing dense concentration of megalop inshore e nvironme nt . although sub­ Red crabs are omnivorous a nd larvae. presumabl) of red c rabs. wh il e surface currents could pos ibl y aid quite versatile in their food habits. s\"in diving in Bahia Magdalena. the ir mi g ra tion (Longhurst. 1968a). Whe n \..ept in aquaria they feed read-

2 ily on fish, using their chelipeds to break off small pieces of fte h . They also use the chelipeds to capture small prey like copepods (Longhurst, Loven­ zen. and Thoma, 1967). They a re unusual in that they can a lso feed directly on micro copic plants a nd a nimal (plankton) by filtration. Analy­ se of stomach contents of red c rabs reveal that the pelagic phase feeds primaril) o n small ph) to- and zoo­ plankton (Longhurst. et a l. . 1967: Bekl emishe\, 1960). In the wild. red crabs can be ob­ sened swimming backward a nd up­ ward b) rapidly fle,ing their abdomen . At or near the surface the) stop sWImming, stre tch out a ll their legs­ thus creating a parachute effect be­ cause of the nume rous fi ne hairs on the legs-and float slow Iy downward while using their fi lteri ng mechani m to feed (Fig. 4). Benthic red crabs probabl) feed pnmarily on detntus by rakIng up sedIments with their feet and mouth parts (Bo)d. 1962). BeklenllShe\ (1960) de~cnbed a peculiar beha\lOral pattern of red crabs whIch may be related to feedIng. About one-thIrd of th e red crabs he obsened swam upside down. and the maJont) of the~e crabs appeared to maIntain them~elves at thc ~urface b) hangIng on the ~urface lilm w-Ith theIr leg~. presumabl) feedIng o n .,urface plankton . Predator., of rcd crab., arc man) and vancd. Whcrc\er thc) arc found , red crabs arc eaten b) .,klPlack tuna. ye ll owfin tuna. and albacore (Aher­ son. 1963 : r-.lcHugh. 1952). man) other speclcs of fi~ h e~ . .,e\cral .,pecics of bIrds. sea lIon., (Bo)d. 1(67). and Figure 4.-Red crabs swimming and feeding of rcd crabs a long the coast appears some whales (Matthew-s. 1(32). Be­ near the surface. Crabs with outstretched legs are slowly drifting downward, while those to correspond to the plankton-rich cause of th eir ablilt} to fecd on ph}to­ with chelipeds extended in front and abdomens waters derived from coastal upwell­ plankton, red crabs form an Impo r­ flexed are swimming upward . ings (Longhur,t. 1967: Blackburn . tant a nd ra ther direct intermediate 1969). lInk in th e food cha in from primary ren t carries some crabs far out to sea Large concentrations of red crabs productivity to termInal predators as it swi ngs offsho re from southern have also been reported from the (Longhurst. et al.. 1967). Baja California. Red crabs have been northern part of the Gu lf of California, found over 1,000 mil es from th e Baja and mass stranding~ have occurred o n DISTRIBUTION Califo rnia coast and in two instances beaches there (Boyd. 1967: Cadieux , The distributio n o f th e pelagic o r were also repo rt ed from Central Ameri­ 1973). Whether these crabs form a planktonic phase of red crabs has ca and Pe ru (Longhurst and Seibert, population separate from those off been well-documented (Boyd , 1967: 197 1) . Although th e pelagic distribu­ the west coast of Baja California is Longhurst, 1967. 1968a : Blackburn, ti o n is widespread. dense concentra­ unknown . 1968. 1969). Generally, the center tions are few : the regio n of greatest Seasonal variation in distributio n of distribution is near the west coast abundance is over the continental apparently is sli ght. but annual varia­ of central and southern Baja Cali­ shelf off southern Baja California tions m ay be great (Longhurst. 1967). fornia . The dominant California Cur- (Fig. SA). Distribution and abundance During certain years, strong no rth-

3 Figure 5.-General dlltribulion of pelagic red A B crabs along the Baja California and California r'-'-'- coasts. Darker shading indlcatel heavier con· 1955-1957 i 1958-1960 centralion. A : Normal year. B ' Warm year. I (From Longhurst, 1967.) i i red crah., are hatchcd 10 ofhhore i i \\aters (Longhur\t. 11}67) Examlna­ i tlnn of \amplcs tal-.en hct\\cen 1<:J5X and II}00 IOdicated that more male than female n:d crahs occur In thc planl-.tor (80)d and John50n. IW13). 1 he se\ ratio for the entire timc penod \\as ahout 54:40 In fa\or of male,. 1 anac of all stages arc found In the planktlln Irom January to Jul). \\ith the peal-. In h:hruar) and :-.tarch (Bo)d . 11}0f)) . The greatest concen­ tratIOn \\as found \\lthin a radiUS of 'if) miles of Bahia \tagdalcna (F-ig . 01. In thiS arLa. up to 42.00() lanae per 1.\00 CUOIC yards of \\ater \\ere caught In planl-.tlln net5. \\hlle oUhide the Mea dunng the same period rJanu­ ar) through Jul)) the a\erage catch \\a, onl) fi\e lanae per 1.300 LUblC ) ard Gnlll-.e the pelagic en\lronment. the benthic habitat of red crab\ ha \\ ater tra\\1 at the Channel hla nd, not been e\ten~l\el) sune)ed. For near 1 0, Angele, 0) the California se\ eral ) ear~. SCientists of cnpp I n-

UN TED STATES Department o f I-J\h a nd Game (I--.en­ 5tltutiOn ot Oceanography ( 10) ha\e neth ;--.t a l'> . Dept Fl'>h and arne. 350 occa~lonall\ conducted cruise 10 in­ G olden Shore. Long Beach. allf . shore waters of central and southern pers cOlllm) Red craos \\ ere e\ldent Baja alifornla uSlOg otter tra\\ls o ff 50uthern California throughout to capturt: benthiC fi he5. t time the rest of the year and into the spnng the presence of red crab~ made It MEXICO mo nth5 of 1973 Se\eral rna s strand­ Impo~5lble for 10 personnel to traw I lO gs of red crabs occu rred on coa tal for fi~hes (Don Docl-.lOs. 10. La

"( beaches near Los A ngele and the Jolla. ald' . pers comm .). Red crab Channel Islands Commercial fhher­ \\ere caught from Bahia eba tlan men reported large numbers 10 the Vizcaino to Cabo San Lucas. Depths \\ater and In the stomachs of fi he5 of the areas tra\\led were generall) that the, caught. Red crabs \\ere also between 30 and 100 fathoms. found near Monterey. Calif. dunng Parl-.er (In Longhurst. 1968b) found spring of 1973 (Jerome Spratt. Cali­ benthic red crab a far north a fornia Dept. FI h and Game. 220 I Bahia eba tian Vizcaino (about lat Garden Rd.. 10nterey. Calif.. pers. 28° N). which appears to be the north­ comm.'. ern limit of the crabs. except during Red crabs are found mostl) in \\arm ,ears when both benthic and 59-70° F seas. but have also been pelagic phases are found off California. Figure 6.-Map of Baja California, showing important landmarks on the west coast. found in temperature of 48-82 ° F The greatest depth at which red crabs (Longhurst. 1967). Crabs found in were found was 200 fathoms. Per­ ward transport of water along the offshore areas are generally small er kin (ibid) reported that the crab west coast carries red crabs to south­ than those found close to hore. This were extremely abundant in waters ern California and occasionall y as suggests that they may have originated deeper than 80 fathoms. far north as central California (Fig. in inshore waters but were swept off­ In ovember-December 1960, Boyd 5B) . The period 195 8-60 saw this shore as larvae . However. since egg­ (1967) used a small otter trawl to happening. and most recently during bearing females about 0.5 inch in sample the bottom from about lat 25 ° the summer of 1972. red crabs were carapace length have also been found to 31 ON . No red crabs were found caught in large numbers with a mid- offshore. it is likely that at least some north of Punta San Eugenio (Iat 2r

4 Table 1.-Proximate composition of uncooked the planldon o r in bottom samples red crabs. Bel-.lemishev (1960) calculated that from sha llower area. Boyd a lso sug­ there were more than 300.000 tons MOIsture 7689 C, Total Crude Protein 10 61 c( gests that in shall ow waters. crabs of red crabs In an area of about Total LIpid 248<""r which are planl-.tonic at ni ght may 77.000 square miles off Baja Call­ Ash 629'( Iodine No of Fat 175 ,ettle o n the bottom during the day forma which was surveyed by the Crude Fiber (Chi t'") 500'( ~ hen suitable bottom is avai lable. Russian research vessel Vilyu~. In Salt (NaCI) 1.25'( Vola tine A Cid Number 16.8 A cruise in Apnl 1973 by S IO January 1960. Ba ed on catch rates Volatile Base N 003'( discovered that red c rabs are abun ­ pH 688 aboard the NMFS research vessel Total Carbohydrate dant as far south as Costa Ri ca (Don DUI'leI SWrr jordull catches up to 20 (as glucose) 094'( Docl-.ln s. SIO. La J o ll a, California. tons an hour could be expected with pers. cOlllm.). Between about lat 11- a 50-foot midwater tra~ I (National Table 2.-Composition of cooked and un­ 12 . at depth, of about 60-100 Fishern13n. 1970). It is c lear that In cooked red crabs. fathoms. the crabs ~ere numerous areas where red crabs are concentrat­ CompoSition Cooked Uncooked enough to eau~e problems In retneval ed. the catch rate is limited onl) Percent of the bottom tra~ I used. and sub­ by the size of the gear that a vessel sequent separation of deSired fish can handle. It should be pointed out. Total solids 16 .9 234 Total lipids 0.8 30 specimens from the crabs however. that concentrations y ieldi ng Ash 6.2 82 such high catch rates are not found ABUNDANCE throughout the range of the species.

Table 3-Material balance of cooked and Because vel) Ie"" quantitative data Longhurst (1968b) suggested that uncooked red crabs after passing through a are available. no estimate of the total the four millton yellowfin tuna caught meat/shell separating machine. abundance of red crans can be made. b) the United States and 1\1 e'.lcan Cooked Uncooked The catch ""Ith a small (IO-Ioot head­ fisher) off Baja Cali fornla In 1960 Wt of crabs 2661b 29.51b rope) otter tra\\1 tl)~ed for 25 min­ consumed 2.000 tons of red crabs Wt of discarded she I 841b 132 Ib utes at 2 I-.noh ~as anout 400-500 It Wt of meats & Viscera 1781b 881b each day IS eVident. ho""ever. that Physical loss 031b 7.5 Ib pounds (Boyd. I 967) Thu~ a conven­ a declillal pOint was misplaced In his Percentage yield 67 a 30 a tional shnmp tra"" I (55-foot head­ rope) would be e'.pected to catch Figure 7.-Salmon-rearing pens located at about 2.500 pounds under Similar Squaxin Island, Washington. (Photo by J. Table 4.-Composillon of cooked and un­ conditions. Fraler, STOWW. ) cooked red crab meat and viscera fraction.

Cooked Uncooked

Percent

SOlids 129 163 LIpid 10 38 Ash 37 33

Table 5.-Compositlon of protein concentrate prepared from meat and viscera.

CompoSition Cooked Uncooked

Percent

Prote," 1 (N X 625) 614 593 LIpid a as 0.05 Ash 233 248 'Not corrected for chitin ------

50' ). Dunng a cruise In Apnl 196 1, he fou nd crabl> south of lat 24 . In running a transect of trawltng stations from near shore to the edge of the continental shelf, Boyd found red crab between 41 and 164 fathoms. At the latter depth , the crabs mea­ sured an average of 1. 10 inches cara­ pace length, with a maximum of 1.26 inches. These crabs were pre umed to be strictly benthic, because no crabs over 1.02 inches were found in

Figure a.-Pan-alled salmon ready for market. (Photo by J. Fraler, STOWW.)

5 calcu lation because the data on whi ch of carotenoid pi gments, a nd even pap­ trawl s loa ned by M FS, Lady O/~a that estimate was based howed th at rika . The salmon-rearing indu try fis hed for 4 day at the Channel the 567 yell owfi n sto mach sampl ed ha grown drama ti ca ll y recent ly (Fi g . Islands . T otal catch was a di appoint­ contained a total of 30.9 quarts of 7 and 8) and th e producti on from ing 500 pound of crab , but valuable red crabs (A lver on. 1963). which three pri vate fi rms was projected to ex peri ence was gai ned . amounts to 0 .05 quart s per fi sh rather reach 4-5 m ill ion pounds by 1974 Since red cra bs are di stributed pri ­ than 0 .5 qua rts a indicated by Long­ (Wagner. 1972>. maril y near Baja alifornia. th e hurst. Thus his estimate is too hi gh Red crabs were sorely needed fo r Mex ican G overnment wa petitioned by a facto r of 10 . However . when one furth er research , and th e a li fo rnia to a ll ow Lady O/~a to fi h fo r crab con iders th e consumptio n by the Department o f Fish a nd Game's re- in Mex ican wa te r . Owing to th e entire populati o n of yellowfi n. as well earch ves el A Imha provided two one­ experi mental nature of the fi hery, as skipjack and cores of other preda­ ton loads. The crab~ were used pri ­ Mex ican officials granted the Lady tors which feed on the crabs . it IS maril y by the M FS's PaC ific Fishery O/,?a their permi SS ion in exchange fo r evident th at the stock o f red c rabs Products Technology Center in eattl e data on a ll aspect of the fis he ry . Thus i huge. to stud) cha racteri tics of red crab on I I A pril 1973, the vessel left pertaining to ha ndling and storage a n Di ego to launch th e fi he ry in UTILIZATION aboard fishin g vessels. tudles of th e earn est. Be Ide Bi xle r. c rewma n Dave effects of the crab in the diet of Johnson. and th e a uthor. Ma ri o The abundance of th e red crab re­ rainbow trout brood stock were al 0 Yoshi da. a tudent from the Escuela source has been common kn owledge begun at the University ofWa hIngton . Superior de C lencias Ma rina in En- to the fis hing industry for years. How­ Late In 1972 the mall T ribes enada, MeX ICO. went alo ng as official eyer . no attempts we re made to devel­ Organizati on of Western Washington observer for the Mexican Government. op uses fo r the crabs. prlnclpa ll } (STOWW) reque ted aid from M FS Fi hing operati ons started at Punto because of the small amount of meat In getti ng a upply of red crabs fo r Abreojo (Ia t 26 45 ' : I 13 ° 40'W ) in the tail. To explore possible uses. feeding pen-reared almon . STOWW v.here Fa th ome t e r ~ readin g a nd \i ual M FS ran a senes of a nal) es on i a enlce organizatio n providing Ightings indicated the presence of red crabs to proVIde potential use rs economi C, socia l. a nd administrative red crabs. The fi r t ign of la rge with basic data. Tables 1-5. repo rt ed senices to the me mbership of 18 numbers of crabs near th e urface pre\ lousl} In National Fisherma n Indi an tnbe. Red cra bs had been v. as In waters discolored by a bloom (1970). gl\e results of these analy es pre ent In southern Califo rni a wa te rs of plan kton. probably COIlYlllllll.\ . by MFS and b} a pri vate firm . ince summe r. and In ea rl) 1973 the} an organi sm whi ch produce th e The results att racted the attenti on were still being tra nded o n beache widely known -- red tide:' Ma ny crab of a pet food manufactU ring fi rm while fis hermen reported large num­ were seen repeatedl } swimming to th e which deCided to explore the po si­ bers near the Channel Isla nds . Brent urface and th en inking lowly. then bi lit} of I ncludi ng the c rabs in a Bixler. owner and ca ptain o f the fish­ swimming upward again . U ndoubted­ special pack. Accordingly. it ordered ing vessel Lady Olga , agreed to try ly the c rab were feeding o n th e con­ a sample shipment from Matt May. fis hing for red crabs for STOWW af­ centrated plankto n. Boyd ( 1962) also then ov. ner of the ves el A lIleriClIIl ter learni ng of th e potential growth report ed red c rabs associated with Eagle. and the commercial fis her) of the fi hery . I n February . eq ui pped was born Fifteen hundred pounds of 2 Reference to trade names does not Imp\) wi th both la rge and sma ll mi dwater endorsement by the Na!lona\ Man ne FIsher· red crabs-enough for studie on con­ les Sen ice., OAA. sumer (cats) acceptance-we re caught . 3 . POLYP ROPYL ENE LI NE during the first tnp in July 1970. "0 MFS provided the gear fo r catching TOP . " " ' " '"'''' the crabs. and the autho r went along ~ ~""" to study the crabs a nd fis hing opera­ tions. Meanwhile. the NM FS's N orthwest """~~} Fisheri es Center in Seattl e di scovered 30' that when red crabs were included in th e di et of pen-reared Pacific salmon (Oncorhynchus sp.). the flesh ga ined its natural reddish tint (A nthony N ovotny. NMFS, N orthwest Fishe r­ ies C enter, pers. comm .). Without the crabs, the flesh remained white . Carotenoid pigment , which red crabs contain in quantity (Wi lkie. 1972), caused th i effect. Earli er efforts to induce red-colored flesh included feed­ Figure 9.-Midwater frame Irawl used in ing the salm on with va rious sources catching red crabs .

6 Figure 10.-Daytime traces of pelagic red crabs on a " white line" Fathometer . A: Bahia Magdalena. Crabs on and near botlom. The inverted " V" traces were probably fish . B : A Thetis Bank. Crabs on Ihe botlom as well as near the surface. The " white l ine" is occluded because of the densily of the c rabs. T 121m Gonyalllax, which produces toxins I fatal to many fishes and invertebrates. -L Apparently the crabs are immune to the toxi ns . A few days of fishing near the area proved that commercial quanti­ B ties were not present. For this trip a midwater frame trawl with an 8 X 10-foot opening was constructed (Fig. 9). The webbing was simply attached to the four sides o f the frame and tapered to an end openi ng hal f the I size of the mouth . A conventional 301m cod end was not sewn into the end. A pair of 40-pound depressors kept the opening vertical during tows. The net worked satisfactorily in catching crabs, but bringing the crabs aboard proved difficult because the webbing was too light. and reinforcing rib­ line were insufficient to ho ld the weight of the crabs. Following 4 days of unproductive searching a nd fishing, we entered may move both along the sho re and The cruise experience confirmed as Bahia Magdalena. Several Mexican s li ghtl y offshore or inshore. They well as contradicted publi shed accounts shrimp ves els were anchored in th e often stayed very close to th e bottom regarding the crabs. T he size of the bay, and we learned from their crews during the day (thus making it difficult crabs corresponded closely to that th at crabs were so abundant in the to use a midwater trawl), and moved given by Boyd (1967). Samples taken bay that at times it wa impossible up somewhat during the late after­ from various localities showed re­ for them to trawl for shrimp. A couple noon , although at times they hovered markably little difference in ize, of hours of scouting confirmed their at mid-depths throughout the day. ranging from 0.59 to 1.02 inch es a nd reports. The Fathometer showed dense They evidently moved to the surface averaging 0.85 inches in carapace traces (Fig. 10) and hundreds of birds in large numbers at night, judging length at all areas fis hed. Sample sat on the water feedi ng on red crabs, from the feeding activity of birds in from Bahia Magdalena taken at 0900, while others flew over th e water and the earl y morning hours. Peli cans do 1500, and 1800 hours showed no neatly picked up crabs at the urface . not appear to feed on red crabs, and di fference in range or average size. Fishing began the next day, and when they are among a group of diving At Bahia Magdalena, some indica­ by the end of 5 days the hold was and working birds their feed would tions of diurnal migration were noted, fi lled with 42,600 pounds of red crabs invariably be small baitfish rather but even during daylight hours the (Table 6) . Much time was lost owing than crabs. Boyd (1967), however, crabs did not settle directly on the to inadequacy of the net. The catch included pelicans a mong the predators bottom (Fig. lOA). Rather, they typi­ rate could easily be doubled with the of red crabs. cally were distributed from the bottom proper net. Because the crabs had to Table 6.-Summary 01 fishing activity aboard Lady Olga, 16·24 April 1973. be shoveled into plastic bags before Avg Avg being placed in the refrigerated fish Bottom Surface No duration catch Total hold, handling and storage was also depth temp of of tows per tow catch Date Locality (fm) (F) tows (min) (Ib) (Ib) time-consuming and laborious, and 4/16 Pta . Abreo)os 10·15 59 4 59 138 550 6-8,000 pounds were about maximum 4/17 Bahia San Juanlco 10·15 62 6 50 392 2,350 for a IS-hour workday. 4/18 Bahia San Juanlco 7·13 62 2 62 825 1,650 4/19 Bahia San Juanlco 5·10 62 1 50 100 100 Several behavioral characteristics of 4/19 Bahia Santa Mana 20·22 62 1 32 100 100 red crabs and bi rds were learned 4/20 Bahia Magdalena 5·15 64 4 13 1,5 00 6 ,000 4/21 Bahia Magdalena 5·15 64 9 37 833 7,500 which proved useful in find ing the 4/22 Bahia Magdalena 5·15 64 6 31 1,350 8 ,1 00 crabs. T he crabs do not stay in the 4/23 Bahia Magdalena 10·15 64 4 38 3 ,150 12,600 4/24 Bahia Magdalena 12·15 64 2 30 1,825 3,650 identical area from day to day. T hey 39 40 1,092 42,600

7 " . of red crabs may lose their effec­ tiveness. Another aspect is directed toward separating the crabs into two fractions. one with high protein and carotenoid pigments (for salmon

~-- feed). and another with low protein and high chitin for other uses (Spinelli. Lehman, and Wieg. in press). -" Even if red crabs become an integral part of the diet of pen-reared salm on. -=".;;a~-: - the total tonnage needed for th is -~~- ~<-... -"~ - purpose will only be about a hundred ----Figure 11.-Birds sitting on and flying low numbers (Fig. 8). Fish caught there tons per year. Other uses wi II have over the water, feeding on red crabs at the surface. Most of the birds are juveniles . had stomachs full of red crabs. and to be developed in order to sustai n a many crabs were seen near the su rface. fishery for crabs. The use of the flesh­ Somewhat to the north of Thetis coloring property can be carried over to about midwater. Whether or not Bank in deep water at night. Fathome­ to other fishes and animals where the crabs near bottom were sitting ter traces of crabs were solid from external rather than internal coloration on each other is not known . the surface to a depth of 30 fathoms . is desired, for example in aquarium BOyd (1962) found that wave and fishes. Research is needed. however. FUTURE OF THE FISHERY wind action was responsible for strand­ to determine the effects of red crabs ings of red crabs on beaches. W e Development of a new fishery is in the di ets of various species of found. however. that crabs were being always difficult. Even if the availabil­ animals. In rainbow trout. at least. stranded daily in a quiet cove where ity of a resource is known. studies are red crabs produce brilliant external the wind and v.a\es moved offshore sti ll necessary on all aspects from coloration as well as pink flesh (Loren rather than toward the beach. It fishing to marketing. In the case of Donaldson. University of Washington, seemed that the crabs were being red crabs. the task is even more dif­ pers. comm .). If the same results can stranded b) the recedi ng tide rather ficult because conventional uses for be achieved with aquarium fishes. and than b) v. ave action. Cadieux (1973). crustaceans do not apply. and new if the feed can be packaged in a on the other hand. observed many uses have to be developed. The future convenient form this might become crabs actually walking out of the of the fishery lies in the success or a major use for the crabs. v.ater to die on the beach. Hundreds failure of these new uses. The chitin found in red crab shells of birds lined the beach where the Certainly one of the more impor­ cou ld possi bly form the basis of a crabs were washed ashore (Fig. 3), tant areas of research is the value of major industry. Chitin is the structural but they did not appear to feed on red crabs as a coloring agent for pen­ material that holds together the shells crabs on the beach. The bi rds oc­ reared salmon. Current research being of crustaceans. Presently a pilot plant ca ionall) took flight and picked up conducted by NMFS in Seattle on near Seattle. Wash . is testing the dead crabs that were awash in shallow the optimum feeding rates and times feasibility of extracting chitin from water and returned to the beach to will provide data necessary for evalu a­ shells of crustaceans. Chitin is similar eat them We noticed also that most. tion and economic comparison with in nature to cellulose and can be used if not all. of these birds were adults. other sources of carotenoid pigments. in place of cellulose in some products. whi le most of the birds feeding on Three of the five commercial firms From chitin also. a material called live crabs av.a) from the hore (Fig. in the United States now rearing chitosan can be derived. opening up I I). had the mottled markings of salmon have enough supplies of red a surprising variety of uses in paper­ Juvenile birds. crabs to also undertake such feeding making. food. pharmaceuticals. sewage Our fishing was confined to shallow. experiments . If results are favorable. treatment. and many other applica­ protected bays because of high seas. red crabs may become an important tions (Pacific Northwest Sea. 1973). We fL)und e\ idence of large concen­ component of the salmon's diet. I ncl usion of red crab in pet food tratiOns of crabs in deeper offshore A long with this research other is still undergoing research. If results \\ater~. however. About 15 miles north work related to use of red crabs as are favorable. the crab market could 0 l)t Cabo San Lazaro (lat 24 -+8 ' salmon feed is being done at NMFS increase severalfold and the fishery k)ng 110 IS'W) during daylight. the Pacific Fishery Products Technology would be assured a sound base. Of Fathometer Indicated large number Center at Seattle. One aspect is to course. with the cost of fis h meal of crabs In the top 10 fathoms. At at tempt to stabilize the carotenoid rising dramatically. the possibility the ~urface. narrov. but long windrow pigments of red crabs so that they exists of using red crabs directly as of crabs v.ere oriented in line with can be included in dry pellets. which fish meal despite their relatively low the strong northwest wind. are cheaper to produce than other protein and high fiber content. Recent At Thet" Ban\... about 18 mil es form of salmon feed. Under normal tudies show that high-quality meal nl)rth\\e~t L)f Cabo San Laza ro . we hea t-drying processes used in making can be manufactured from crustaceans tl1und crab, ncar the bottom in large dry pellets. the carotenoid pigments (Meyers and Rutledge. 1971).

8 Another po sible use for the shell re ults. and it IS likel) that se\ eral (adleu\. (. l'r1 'IellO\\I.ul "th .It> of red crabs is in horticultu re. Dried experimenta l products will pro\e u)Ll-tail \\ cst Outd )1 Dec IQ"' ~ 'll Longhur t. A. R. 1%' The pdaglc 1'''' I e a nd pul veri zed crab sh e ll s. when added practicable. It should be pointed out. of PIClIrtlI1IUd, \ pl,III1P' \ 'll'mr '10 ( ru tace.!. Galatheld,le) In the l dillorm to acid soil. would act to neutra li ze howe\er. that although red crabs can Current. Calif. (o"r (),e.JOl, 1 I h In\e t the soil and would also be useful as be caught in international water . the Rep 11 142-1"4 191< a. DIstrlhutl

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