1479NOTES

Some Life History Aspects of the Rock Crab, Cancer irroratus,in the Gulf of Mainel

Jav S. Knouss

Maine Department of Sea and Shore FisheriesI4/est Boothbay Harbor, Maine 04575, USA

Knousn, J, S. 1972, Some life history aspects of the rock crab, Cancer irroratus, in the Gulfof Maine. J. Fish. Res. Bd. Canada 29: 1479-1482.

Rock crabs, Cancer itoratus, were caught in wire lobster traps from 1968 through 1971at Boothbay Harbor and in 1969 at Casco Bay, Maine. Females dominated the annual catches(except in basco Bay) and width classes from 61 to 90 mm; while males were predominantabove this size range. Rock crabs from Casco Bay were heavier at a given width than thosefrom Boothbay Haibor, Soft-shelled females were caught mostly in the fall, while soft-shelledmales appeared most frequently in late winter and early spring. The occurrence of newly berriedfemaleizuggested that siawning (egg extrusion) took place in late fall and early winter, andhatching oiiurred in spiing. Most female crabs attained sexual maturity between 70-80 mmcarapace width, but a few matured at widths less than 70 mm.

Knousr, J. S. 1972. Some life history aspects of the rock crab, Cancer irroratus, in the Gulfof Maine. J. Fish. Res. Bd. Canada 29: 1'479-1482.

On acaptur| des crabes communs, Cancer irroratas, dans des casiers m6talliques d homardsd Boothbay Harbour de 1,968 iL 1971et dans la baie Casco en 1969. Les femelles pr6dominentdans les prises annuelles (sauf dans la baie Casco) et dans les classes de largeur de carapace de61 d 90 mm: au-deld de cet intervalle, les miles sont plus abondants. Pour une largeur donn6e,les crabes de la baie Casco sont plus lourds que ceux de Boothbay Harbour. Les femelles dcarapace molle sont captur6es surtout en automne; les mdles dans cette condition se ren-contrent plus fr6quemment d la fin de I'hiver et au d6but du printemps. La pr6sence de femellesnouvellement oeuvdes suggdre que la fraie (lib6ration des oeufs) a lieu d la fin de l'automneet au d6but de I'hiver, et feclosion au printemps. La plupart des femelles atteignent la maturit6sexuelle d une largeur de carapace d'environ 70 a 80 mm, bien que quelques-unes atteignentce stade d des largeurs inf6rieures d 70 mm.

Received March 14, 7972

Ar,oNc the Maine coast, the abundant rock crab Methods and materials-Rock crabs were collected

(Cancer irroratus) supports a small fishery. The with _rectan^gular vinyl-coated wire lobster- -traps (l X

i970 catch was only t,ilt,tCOlb, valued at S-89,6t1. I and I X 2 inch mesh) in coastal-waters of Maine near

Fishing is primarily incidental to the lobster n.rt..v. Boothbay.Harbor from Mav 1968 through December

rhiJstudy was undertaken because or the rk;ii: i:1J',X?$]i":1f:"",#"if;X"::ffi:l"iYl-#1t.11:hood offuture expansion ofthe crab fishery and the ,trit* i"t.irp.ir.J *itfitock outcroppings in depthsscarcity of information on the species. This investi- raneins frorn- 15 to 60 ft.gation, which has utilized data collected incidentally dpon capture, each of the 7174 crabs was sexed andto the Lobster Research Program of the Maine measured prior to its return to the sea. Carapace widths

Department of Sea and Shore Fisheries, is con- measured between the two most posterior notches on the

cerned with: (1) size composition and sex ratio of anterolateral border were recorded to the nearest milli-

annual catches; (2) seasonil occurrence and sire oi meter. Crabs were classified as newly molted if ventral

ovigerous females; (3) incidence of molting; an"J :-:'lilt:?^f-:":it"::and/ortheproximalsectionsof the

1+; widtn-weight ielitions ilJ*:T;'ff,fii,'31'*',il'iLx?; d;11!".,,":?1"'#u'l;the swimmerets (indicating recent hatching), were also

lThis study was conducted in cooperation with the noted.Department of Commerce, National Marine Fisheries Width-weight relations were based on 272 crabs (145Service, under Public Law 88-309, as amended, Com- males and 127 females) taken in Casco Bay in July 1969mercial Fisheries Research and Development Act, and 168 crabs (47 males and 121 females) collected nearProject 3-14-R. Boothbay Harbor in July-August 1969. Wet weights

were recorded to the nearest 10 g. The regression ofPrinted in Canada (J2472) weightonwidthwasflttedbythemethodofleastsquares

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1480 JOURNAL FISr{ERIES RESEARCH BOARD OF CANADA, VOL. 29, NO. 10, 1972

using the logarithmic transformation log1sW : logna|blo916l-, An analysis of covariance was employed todetermine whether or not the regression coefficients ofmales and females were signiflcantly ditrerent.

Size composition-Since the size compositionof annual catches from Boothbay Harbor did notvary year to year, catch data were combined from1968-:71. Width-frequency histograms clearly re-vealed the marked size disparity between males(generally larger) and females (Fig. 1). Phillips (1939)concluded that mature female Cancer crabs from thePacific coast are usually smaller than mature males.Males from Casco Bay (mean 107 mm) were largerthan males from Boothbay Harbor (mean 92 mm).The effects of gear selectivity are manifested in thehistograms by: (1) the progressive decline in numbersof small crabs, and (2) the pronounced modes whichdenote size where crabs are fully vulnerable to thegear. Although these conspicuous modes occurredat smaller sizes for females than males, it seemsunreasonable to assume that males would becomefully vulnerable to the gear at a larger size thanfemales. I attributed this dissimilarity in the sizedistribution to smaller males being unavailable tothe gear. Small males (less than 90 mm carapacewidth) may concentrate themselves in shallower ordeeper water than that sampled.

Sex ratio - There were more females than malesin the Boothbay Harbor catch, 196811 ; conversely,there were fewer females than males in the 1969catch from Casco Bay (Table 1). In both areas,

Frc. 1. Width-frequency distributions of rock crabscollected at Boothbay Harbor (1968-71) and Casco Bay(le6e).

Taglr 1 Total number of rock crabs and percentfemales by size class for Casco Bay 1969 and BoothbayHarbor 1968-71.

Boothbay Harbor Casco Bay

Carapacewidth(mm)

Total Femalesno. (%)

Total Femalesno. (%)

2t-3031+041-5051-6061-'7071-8081-9091-100

101-r l0111-120121-130

Total

J

7'761,

273153128781335

+ t o

534

6632

100J J . J

3 5 . 360.78 1 . 387 . 566 .022 .61 . 500

6 2 . 1

10;92.397 .678 .02 . 5000

3 2 . 1

females dominated the size classes between 61 and90 mm. For carapace widths greater than 90 mm,males outnumbered females,

Disparities in the overall sex ratios may be ex-plained by: (1) the spatial separation of males smallerthan about 90 mm carapace width from the segmentof the population available to the gear; (2) differencesin sex ratios between sampling sites (a cursoryanalysis indicates differences in sex ratios betweensampling stations as well as seasonal changes withinsites); and (3) possible differences in mortality rates(fishing mortality is greater for males since theyattain larger sizes while most females never reacha harvestable size). Fluctuations in the sex ratio withsize may also be assigned to the unavailability ofsmall male crabs and to a retardalion or cessationin the growth rate for females after the onset ofsexual maturity. The female Dungeness crab,Cancer magister, of the Pacific coast has been ob-served by Cleaver (1944) to slow down its growthrate with the onset of maturity, while members ofthe spider crab family are known to terminate molt-ing at maturity.

Maturity - A relative index of size at first matu-rity, time of spawning, and egg hatching was basedupon the occuffence of egg bearing and egged-ofl(eggs have hatched but egg cases still cling to theswimmerets) females in the monthly samples.Berried females (width ranged from 62 to 99 mm)appeared most frequently from February throughMay with a gradual decline to August and then amarked reappearance in November and December

:I

13125508 l

139l l 7

Z J

549

z=o

U

zU

BOOTHBAY HARBORFEI\4ALEStr (1968:71)

MALES ai =817 I l -_ i . szAN=4i l6 l l l " l N-25oel=oi l t l l l q.0.22

FEI\4ALES I I" MALESx=77:t _f l l ' l i . lo?oN=r76 l l l l l L N=3738 0.38 lll ll I t=ouo

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MonthTotalno.

(Table 2). Egged-off females (width ranged from55 to 96 mm) were most abundant from June throughAugust with a conspicuous decline in the followingmonths (Table 2).

These periodical appearances of berried and egged-off females indicate that egg extrusion occurs in latefall and winter from which time the eggs are carriedexternally until hatched the following spring. Thisis supported further by the observation of newly

Tmrn 2. Total number of female rock crabs with themonthly percentage of berried and egged-off femalescollected at Boothbay Harbor from 1968-71 and July1 97 O-l 1, respectively.

Berried Egged-off

1481

spawned orange eggs in late fall-early winter, fol-lowed by the more developed greyish-black eggs inlate winter and spring. Cleaver (1944) noted that theDungeness crab spawned in the late fall and theeggs were hatched in the spring.

Molting -Information on molting was first col-lected in August 1969 (Table 3). The data indicatethat months of peak shedding did not coincide formales and females. Soft males appeared mostfrequently during February and March and softfemales in the fall.

Width-weight relation - The regression of totalwet weight on carapace width was calculated formale and female rock crabs sampled at Casco Bayand Boothbay Harbor. The equation used wasW : aLb, where W : wet weight in grams, L :carapace width in millimeters, and a and b areconstants.

Since analysis of covariance on the regressioncoefficients (Steel and Torrie 1960) indicated that

Ftc. 2. Comparison of rock crab width-weight relationsfor sexes combined from Boothbay Harbor and CascoBay. The curves represent weights calculated from theregression equations. The regression equations for Booth-bay Harbor and Casco Bay are, respectively, 1og19W : -3.39 + 2.82 log1s L and logls W : -3.60 +2.94 logrc L,

(%) orcatch

(%) orcatch

Totalno.

Jan.Feb.Mar.Apr.MayJuneJulyAug.Sept.Oct.Nov.Dec.

035

18253

116500824

I 581s943091,7092

020.013.2t 3 . 22 1 . 67 . 82 . 10 . 700 . 65 . 95 . 4

_a

5+

te582631s9680

13731

I19.330 . 814.92 . 9t . J

0 . 70

aNo samples taken.

Taerr 3. Percentage of soft-shelled crabs in monthlysamples collected at Boothbay Harbor, 1.969-71.

Males Females

I

lrl

=

MonthTotal %no. shedders

Total %no. shedders

Jan.Feb.Mar.Apr.MayJuneJulyAug.Sept.Oct.Nov.Dec.

ri:11038

1081 1 8J t I

55219861,J I

60

3 1 . 029.12 . 66 . 50 . 91 . 91 . 60 . 502 . 73 . 3

ie681 1J +

101582

1 1 8 361685L J

68

2 . 82 , 7

0000 . 90 . 83 . 48 . 200

aNo samples taken.

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1482

width/weight ratios of males and females from thesame area were not significantly different, sexes werecombined by area. The regression coefficients(a and b) were:

Boothbay Harbor Casco Bay

a b a b-3 .39 2 .82 -3 . 60 2 .94

Casco Bay rock crabs were heavier at a givenwidth, particularly at the larger sizes where malespredominated, than Boothbay Harbor crabs (Fig.A.

JOURNAL IISHERIES RESEARCH BOARD OI CANADA, VOL. 29, NO. 10, 1972

Acknowledgments -I am grateful to Messrs R.Hanley, G. Brackett, R. Nunan, S. Ham, and A. Dollofffor their assistance in field collections and data com-pilations. I would also like to thank Mr J. C. Thomasfor his suggestions and review of this manuscript.

CrrrvEn, F. C. 1944. Life history and habits of thecommercial crab, Cancer magister. Wash. State Dep.Fish. Biol. Circ. l: 2 p.

Pnrnrps, J. B. 1939. The market crab of Californiaand its close relatives. Calif. Fish. Game (25) 1:29 p.

Srrrl, R. G. D., eNo J. H. Tonmr. 1960. Principlesand procedures of statistics. McGraw-Hill Book Co.,Inc., New York, N.Y. 481 p.

Fatty Acids in Surface Particulate Matter From the North Atlantic

Davtn M. Scnurrz.c.ND hvns G' QuIt'tN

Graduate School of OceanograPhYUniversity of Rhode Island, Kingston, R.L 02881, USA

Scnur,rz, D. M., nNo J. G. QurNN. 19'72. Fatty acids in surface particulate matter fromthe North Atlantic. J. Fish Res' Bd. Canada 29: 1482-1486'

The fatty acid composition of particulate matter from surface waters in the North Atlantichas been investigated. A high proportion is long-chain polyunsaturated acids, typical of amarine origin. The low relative abundance of iso and anteiso l5-carbon acids indicates littlebacterial contribution to the particulate matter. This fatty acid distribution is in contrast tothat found in estuarine particulate matter, which contains only trace amounts of the long-chain polyunsaturated acids and substantial quantities of branched chain acids.

Scuur,rz, D. M., lNo J. G. QurNr.r. 1972. Fatty acids in surface particulate matter fromthe North Atlantic. J. Fish. Res. Bd. Canada 29: 1482-1486.

Nous avons mesur{ la teneur en acides gras de la matibre particulaire des eaux superfi-cielles de I'Atlantique Nord. Cette matibre est constitu6e en grande partie d'acides polV-i191'tur6s d longue chaine, caractlristique d'une origine marine. L'abondance relativement faibled'acides isi et anteiso 15 carbone indique qu'il y a peu d'apport bact6rien d la matidre parti-

culaire. Cette rdpartition des acides gras diffdre de celle observ6e dans la matidre particulaired'estuaires, qui ne contient que des traces d'acides polyinsaturds d longue chaine et une grandequantitd d'acides d chaine ramifide.

Received January 10, 1972

Tnn lipid fraction of sea surface film samples has portion of the fatty acid composition of phyto-

been investigated by several workers (Garrett 1967; plankton and zooplankton consists of long-chain

Jarvis et al. 1967: Duce et al. 1972). In general, polyunsaturated acids (Ackman et al. 1968; Chuecas

they found an enrichment of surface-active lipid and Riley 1969; Culkin and Morris 1969, l97O).

maierials, e.g. fatty acids and fatty alcohols, at the On R/V Trident Cruise 102 from Reykjavik,

air-sea interface. However, fatty acids found in Iceland, to Halifax, Nova Scotia (August, 1971),particulate matter from surface waters (20 m), have samples were taken at seven stations (Table 1) to

been reported only by Williams (1965), who in- determine the fatty acid composition of open-ocean

dicated that a high percentage of many varied un- surface particulate matter and to compare it with

saturated fatty acids are present. A substantial particulate matter in estuarine samples from Nar-ragansett Bay, R.I. Few data have been published

Printed in Canada (J2394) on the fatty acid composition of particulate matter,

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