NOAA Technical Report NMFS Circular 426 

Synopsis of 

Biological Data on 

the Rock Crab, 

Cancer irroratus Say 

Thomas E. Bigford 

May 1979 

FAO Synopsis No. 123 

u.S. DEPARTMENT OF COMMERCE 

Juanita M Kreps, Secretary 

National Oceanic and Atmospheric Ad ministration 

Richard A Frank, Administrator 

National Marine Fisheries Service 

Terry L Leltzell Assistant Ad..,.- InlSi'atar 1m - sr-er es 
PREFACE 

This synopsis of the literature is intended to summarize all biological 

and biochemical studies involving Cancer irroratus published before 

early 1977. Included are some unpublished observations, drawn primarily from work completed at the U.S. Environmental Protection 

Agency laboratory in Narragansett, R.I. 

The National Marine Fisheries Service (NMFS) does not approve, recommend or endorse any proprietary product or proprietary material 

mentioned in this publication. No reference shall be made to NMFS, or 

to this publication furnished by NMFS, in any advertising or sales promotion which would indicate or imply that NMFS approves, recommends 

or endorses any proprietary product or proprietary material mentioned 

herein, or which has as its purpose an intent to cause directly or indirectly 

the advertised product to be used or purchased because of this NMFS 

publication. 
CONTENTS 

1 Identity .. ........................................................................... 1 

1.1 Nomenclature . . . ................................................................. 1 

1.11 Valid name ...... .... ................ ....... ...... . ......... . . ............... 1 

1.12 Synonomy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 

1.2 Taxonomy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 

1.21 Affinities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 

1.22 Taxonomic status* 

1.23 Subspecies* 

1.24 Standard common names, vernacular names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 

1.3 Morphology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 

1.31· External morphology .... .. . .... . ... . . ....... . .......... "....................... 2 

1.32 Cytomorphology* 

1.33 Anatomical and biochemical characteristics .................... . ..... . ............ . 3 

2 Distribution ....... ... . ...... . . . . .. . ...... . .......... ..... .......... .. .. ... ... . ...... 3 

2.1 Total area .. . ... ... .. . .. ...... .......... . . . ...... .... ........ . ............. ..... . 3 

2.2 Differential distribution ............... "..... . ........ . .............. ... .... ... ... . . 3 

2.21 Spawn, larvae, and juveniles .................................................... 3 

2.22 Adults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 

2.3 Determinants of distribution changes .... " . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 

2.4 Hybridization .. ..... ........ ..... . .. ....................... . . . ... .. ........ . ..... 6 

2.41 Hybrids.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 

3 Bionomics and life history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 

3.1 Reproduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 

3.11 Sexuality. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 

3.12 Maturity ............... . .. . ............... ... ............... .. ...... . .. . .... 6 

3.13 Mating . . .... . ..... . .. .. .... . .............. . . . ............. . ................ 7 

3.14 Fertilization ...... .. ....... . . .. ............... . ... . . .... ....... ..... .. . .. .. .. 8 

3.15 Gonads ............... . ..................................................... 8 

3.16 Spawning . .. .................................................... . ... . ....... 9 

3.17 Fecundity ........................ .. ................. . ..................... .. 9 

3.2 Preadult phases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 

3.21 Embryonic phase .......................... . .... .. ..... ... .................... 9 

3.22 Larval phases ................................................................ 9 

3.23 Adolescent phases. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 

3.3 Adult phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 

3.31 Longevity ........ .. ........ .. ..... ..... ................. . ................... 10 

3.32 Hardiness ..... ....... . ... .................. . .............. .. ...... . ......... 10 

3.33 Competitors .. .. . ... . . .... .... . . .. ..... . .. . ... . . ............................. 10 

3.34 Predators. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 

3.35 Parasites, diseases, injuries, and abnormalities ...................................... 11 

3.4 Nutrition and growth ... ...... . ..... ................... . ..... ... ................... 11 

3.41 Feeding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 

3.42 Food . . . . .......... . .... . . .......... .................... ....... ............. 12 

3.43 Growth and morphometry. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 

3.44 Metabolism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 

3.45 Molting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 

3.46 Size* 

3.5 Behavior ........................................................................ 16 

3.51 Migrations and local movements ................................................ . 16 

3.52 Schooling* 

3.53 Responses to stimuli .......... .......... .... ...... .......... ... ................ 17 

4 Population .......................................................................... 17 

4.1 Structure. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 

4.11 Sex ratio ....... ...................... . ... ... ......... . . ................. ... . 17 

4.12 Age composition ............................................................... 18 

4.13 Size composition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 

4.2 Abundance and density. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 

4.21 Average abundance* 

iii 
4.22 Changes in abundance ........................................................ . 

4.23 Average density .............................................................. . 

4.24 Changes in density* 

4.3 Natality and recruitment .......................................................... . 

4.31 Reproduction rates ..................................... ...................... . 

4.32 Factors affecting reproduction ............................ . . ......... . .......... . 

4.33 Recruitment ................................................. ............... . 

4.4 Mortality and morbidity ........................................................... . 

4.41 Mortality rates .............................................................. . 

4.42 Factors causing or affecting mortality ........................ .................... . 

4.43 Factors affecting morbidity* 

4.44 Relation of morbidity to mortality rates* 

4.5 Dynamics of population ........................................................... . 

4.6 The population in the ecosystem ............................................ ......... . 

5 Exploitation ............................................................. ........... . 

5.1 Fishing equipment ...... ... .......... ... ......................................... . 

5.11 Gear for capture ..... ............ ............ ................................ . 

5.12 Boats .............................................................. ........ . 

5.2 Fishing areas .................................................................... . 

5.21 General geographic distribution ......................................... ........ . 

5.22 Geographic ranges ......................................................... .. . . 

5.23 Depth ranges .................................................... . .... ..... .. . 

5.24 Conditions of the grounds ............................................... ....... . 

5.3 Fishing seasons ......................................................... ......... . 

5.31 General pattern of season(s) .............................................. ...... . 

5.32 Dates of beginning, peak and end season(s) ........................................ . 

5.33 Variation in date or duration of season* 

5.4 Fishing operations and results ............................................... ........ . 

5.41 Effort and intensity ........................................................... . 

5.42 Selectivity .. .......... ........... ........ . .................................. . 

5.43 Catches .... .... ... ..... ..... ......... .... .................................. . 

6 Protection and management ...... ... .................................................. . 

6.1 Regulatory (legislative) measures .................................................... . 

6.11 Limitation or reduction of total catch ............................................. . 

6.12 Protection of portions of population ............................. ................. . 

6.2 Control or alteration of physical features of the environment* 

6.21 Regulation of flow 

6.22 Control of water levels 

6.23 Control of erosion and silting 

6.24 Fishways at artificial and natural obstructions 

6.25 Fish screens 

6.26 Improvement of spawning grounds 

6.27 Habitat improvement 

6.3 Control or alteration of chemical features of the environment .............................. . 

6.31 Water pollution control .... ..... ........... . ................................... . 

6.32 Salinity control* 

6.33 Artificial fertilization of waters * 

6.4 Control or alteration of the biological features of the environment ........................... . 

6.41 Control of aquatic vegetation* 

6.42 Introduction offish foods* 

6.43 Control of parasites and disease ............................ ... .................. . 

6.44 Control of predation and composition* 

6.45 Population manipulation* 

6.5 Artificial stocking* 

6.51 Maintenance stocking 

6.52 Transplantation 

7 Culture ....... ................................. .1 ••••• ••••••••••• ••• ••••••• •••••••••• 

Acknowledgments ..................................................... ....... .... ...... . 

Literature cited ............. ............................................................ 

* As no information was available, these sections were omitted. 

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Figures 

1. Dorsal view of an adult rock crab, Cancer irroratus Say. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 

2. Percentage survival of Cancer irroratus larvae at constant and cyclic temperatures. . . . . . . . . . . . . . . . . 5 

3. Duration of larval development in Cancer irroratus at constant and cyclic temperatures. . . . . . . . . . . . . 5 

4. Sexual dimorphism in abdomen shape in mature male and female Cancer irroratus ................ 7 

5. Width frequency distributions of Cancer irroratus collected on two cruises: Blesk-30 September12 October 1971, at 48 stations from Cape Cod to Cape Hatteras, and Eastward-24-30 April 1973, off 

coast of North Carolina ........................................................ : . . . . . . . 7 

6. Percentage occurrences of various stages of gonad development in relation to size of 131 male and 136 

female Cancer irroratus captured during a June 1973 cruise in the Mid-Atlantic Bight region . . . . . . . . . 8 

7. Developmental stages of Cancer irroratus ................................................. 9 

8. Metabolic-temperature response curves for the five zoeal and one megalopal stages of Cancer 

irroratus ........................................................................... 13 

9. Cancer irroratus hepatopancreas oxygen consumption as related to temperature for: A) 3°C acclimated 

winter crabs, B) 18°C acclimateCl. winter crabs, C) 3°C acclimated summer crabs, D) 18°C acclimated 

summer crabs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 

10. Carapace width size frequencies of Cancer irroratus collected with crab pots in Delaware Bay from 

November-April 1969-70 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 

11. Rhode Island commercial landings for the Cancer irroratus and C. borealis combined. . . . . . . . . . . . . . . 22 

Tables 

1. Stage of development reached by larvae of Cancer irroratus in different combinations of temperature 

and salinity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 

2. Percentage mortality of each stage of Cancer irroratus larvae reared in 30'/" salinity at different temperatures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 

3. Survival of Cancer irroratus larvae at constant and cyclic temperatures. . . . . . . . . . . . . . . . . . . . . . . . . . 6 

4. Stages in gonadal development of Cancer irroratus .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 

5. Relationships of intermolt stage and gonad development in 267 Cancer irroratus collected during June 

in the Mid-Atlantic Bight. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 

6. Diagnostic features of stages during larval development of Cancer irroratus . . . . . . . . . . . . . . . . . . . . . . . 10 

7. Estimated age and corresponding instars and carapace widths for male and female Cancer irroratus '" 10 

8. Incidence and type of fouling organisms observed on Cancer irroratus captured in June in the MidAtlantic Bight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 

9. Analysis of stomach contents of Cancer irroratus in the Gulf of St. Lawrence, Canada. . . . . . . . . . . . . . . 12 

10. Regressions of body measurements from juvenile and adult Cancer irroratus in Virginia waters ....... 13 

11. Molt cycle stages of CarLcer irroratus. Modified from Drach (1939) .. . ........................... 15 

12. Average carapace widths, absolute and percentage increments, and their ranges for 125 male Cancer 

irroratus. Pooled data for three seasons, 1970-73 ................................. . .......... 15 

13. Average carapace lengths, absolute and percentage increments, and their ranges for 43 male Cancer 

irroratus. Pooled data for three seasons, 1970-73 ................................ . .. ... ...... 15 

14. Average weights, absolute and percentage increments, and their ranges for 57 male Cancer irroratus. 

Pooled data for three seasons, 1970-73 .................... ............................... 16 

15. Cancer irroratus larval carapace measurements based on a diet of newly hatched brine shrimp 

nauplii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 

16. Comparison of mean juvenile and adult Cancer irroratus carapace widths based on: field collections 

and derived regressions, regression values only, Krouse's regression values and Haefner's projections 

beyond stage X, and laboratory reared . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 

17. Percent mortalities of Cancer irroratus adults held at different salinities in the laboratory for 3 days ... 17 

18. Sex ratios, by area and depth, for Cancer irroratus captured in June 1973 in the Mid-Atlantic Bight ... 17 

19. Catch data and mean yields from the Boston Harbor Cancer irroratus population. . . . . . . . . . . . . . . . . . 21 

20. Commercial crab (Cancer irroratus and C. borealis combined) landings and values in Rhode Island 

water between 1971 and 1973 ............................................... . . .. ........ 22 

21. Average concentrations of metals in whole Cancer irroratus adults expressed as ratio of wet weight, dry 

weight, and ash, ± 1 standard deviation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 

v 
Synopsis of Biological Data on 

the Rock Crab, Cancer irroratus ay 

Thomas E. Bigford! 

AB TRACT 

The rock crab, Cancer irroratuB Say, is a common member oflhe bf'nlhic communll\ ulllnJ; Ih 

east coast of North America. The species inhabil~ sandy bottom area, hul rna) o(,('ur lin ~ro\t'l or 

rocky substrates. Bottom trawls and trapping ,ia pot~ frequently) ield, high numh .. " 01 rock 

crabs. growing market may create an increased demand for thi. under .. ploil(d 'p <:1(' • 

Cancer irroratu8 typically occurs from Labrador south to Florida. \\ Ithin thi, ran~( Ihe cr h 

is distributed in specific patterns with respect to temperature , ,alinity, depth. ,ub,lrul" ,und I'm(' 

of year. Many of these factors, plub light, pressure, and gra\lt}, affect lanaI di,lnhullOn , 

The literature includes several papers in general life hi,lory . Puttern, of moiling lind gro\\ Ih 

have been studied in the laboratory and field for all of the life ,tage •. Larval de' "lopnH'nl .lnn 

responses to environmental variables are also well described. 

1 IDENTITY 

1.1 Nomenclature 

1.11 Valid name (from Rathbun 1930) 

Cancer irroratus Say, 1817, J. Nat. Sci. Phila., vol. 

I, p. 59, pI. 4, fig. 2; Smith, 1871-1872 (1873), Rep. U.S. 

Commer. Fish., vol. I, p . 312 (18), 530(236), 546(252); 

Rathbun, 1884, Fish. Fish. Ind. U.S., sec. I, p. 766, pI. 

260, figs. 1-3; Sumner, 1911, Bull. Bur. Fish., vol. 31, 

pt. 2, p. 671; Hay and Shore, 1915-1916 (1918), Bull. Bur. 

Fish . 35: 369-475, pI. 35, fig. 1. 

1.12 Synonomy (from Rathbun 1930) 

Platycarcinus irroratus Milne Edwards, Hist. Nat. 

Crust., vol. I, 1834, p. 414 ; DeKay, Nat. Hist. New 

York, pt. 6, Crust., 1844, pI. 2, fig. 2. 

Cancer sayi Gould , Rep. Invertebr. Mass., ed. I, 1841, 

p. 323 (type-localities, Cape Ann, Nahant, etc.; types 

not located) . 

Platycarcinus sayi DeKay, Nat. Hist. New York, pt. 6, 

Cru t .. 1 44, p . 7. 

Cancer boreali Packard, fern . Boston oc. L at Hi t., 

vol. I, 1 67, pI. 303; not C. boreaLL' timp on. 

Cancer amoenus Connolly, Contrib. Can. BioI., n. s., vol. 

1, 1923, p. 337, text-figs. 1 and 2, pis. 1-4. Not C. 

amoenus Herbst, 1799. 

1.2 Taxonomy 

L' Ennronmenta) Protection Agenc~ , En,.ronmenta) Re. ar h 

Labt1rstOf\, :-"arragan,ett, Rl O~ 2. pre nl sddre . Cenler for. 'at ural 

Area •. 15~5 e\\ Hamp.hlTC A"enue, . \\ , \\ a,hm on, DC -

1 

1.21 Affinities 

Suprageneric 

Phylum Arthropoda 

Cia Cru tacea 

ubela Malaco traca 

Serie Eumalaco traca 

uperorder Eucanda 

Order Decapoda 

'uborder Reptantla 

ectlOn Bral:hy ura 

ub ection Brachygnatha 

Superfamily Brachyrh}'Jlch 

Family Cancridae 

Generic Cancer (from. ationa 1975) 

"Cancer Linnaeu8 1758:625. Type specie C. pagurw 

Linnaeu8 1758. 

"Alpheus Weber 1795:91. Type apeci A. pagu.nu 

(Linnaeus 1795) Not Alpheus Fabriciu 11 

"Pagurus Berthold 1827:255. Type peci p, pagurw 

(Linnaeus 1827). Not Pagurw Fabricl 1775'410, 

"TricMcera DeHaan 1833:4,16. Type peCI T 

bosula (DeHann 1833). 1 'ot TricMcera 1 I n 1 

"Platycarcinus Milne Edward 1 :412. Type I 

P. pagurus (Linnaeu8 1 ). 

"Romaleon Gi tIe 1848:11. ubstitu 

"Metacarcinus ~1ilne Edwards 1 

M. magister (Dana 1 2). 

"TricMcarcinus ~1iers 1 7 ,34, Ibbo ula (DeHaan 1 

Generic (from GI 

"Carapace very wide, flnely 

margin very I ,curv 'ltb 
lobes; gastrocardiac regions marked; orbits small, deep, 

with 2 fissures; front narrow, with 3 teeth, epistome narrow, chelae subequal, with 5 longitudinal blunt ridge8 on 

their outer surfaces." 

Subgeneric Cancer, sensu stricto 

(partially from Nations 1975) 

Front produced; frontal teeth rounded, medial one not 

acute but forming a rounded lobe nearly 88 wide or wider 

than those of the adjacent pair. Anterolateral teeth 

broad, truncate to slightly produced, separated by cl08ed 

fissures; first tooth wider than second. Outer margin of 

anterolateral teeth forming an obtuse angle. Carapace 

and chelipeds smooth. Usually colored with purple or 

crimson spots dorsally on a light brownish-red background, Gulf of St. Lawrence crabs may lack purple, 

with a yellow-brown color predominating and a ventral 

color of pale yellow to cream (Stasko ). 

Specific irroratus 

Nine anterolateral and two posterolateral teeth (usually obscure). Carapace ovular and convex, bordered anteriorly by the anterolateral teeth and posteriorly by a 

raised carina with two teeth. Anterolateral teeth generally shallow, with notches between adjacent teeth ex-

"A. B. 'tasko. Fishenes and .\Iarine :::.ervice. BIolOgical tauon,:-'l. 

Andrews, New Brunswick, Canada. EOG 2XO. pers. commun. Oct 1977. 

........ \ 

' . . ' 

:'" ~ , -.'-

tending into the carapace as !lhort fi ures (fig. 1). 

Haefnerl de cribed pecific morphologIcal difference between ' Lrruratu and imilar crab. 

Chehpeds shorter than fir t pair of pereiopod and 

granulate (not dentIculate); upper margin of meru. 

ending In a short, ubdi tal tooth; carpu with a. harp, 

inner tooth overlapping propodu . Leg long and compre ed, WIth meru (arm), carpu (wrl t), and pUJPodu 

(hand) with the dactylu vi Ible from above on all five 

[Hm of leg .. 'ide margin of fifth and ixth abdominal 

pgmf>nt In male onverglng di tally. Pleopod ,except for 

lir. t und econd (modified for copulatirm), are reduced. 

IJt(J!fno I' • line anterolateral and two po terolatera! tef'th on the carapace, edge of teeth entire. heliped granulate, not denticulate (Fig. 1). 

1.2t Stnndard c mmon name, vernacular 

name 

H ck crab, tone crab, mud crab, and canc r crab. 

1.3 '\Torpho!ogy and de cription 

1.31 r,xtemal morphol) 

A" de nbed 8tJo\'e in eetion 1.21. 

F 

gin a 

P'lIn • \a 

to Idenl flcatl n \ rMce :: 10. G OU Iff 

Figure I.-Dorsal view of an adult rock crab, Cancer irroratus Say. (From Rathbun 1930.) 

2 
1.33 Anatomical and biochemical characteristics 

Skobe and Nunnemacher (1970) studied the fine struc- . 

ture of the circum esophageal nerve. One rock crab (carapace width 65 mm) had a connective nerve of 0.29 mm in 

diameter. Within the connective were numerous fibers, 

,ranging from <1 ~ (fine) up to 25 ~ (large). Fine fibers 

«1 ~) and small (1-3 ~) fibers comprised the majority of 

all fibers with 41 and 47%, respectively. Medium-sized 

Ibers (3-9 f-L) accounted for 11 %, and only 1 % of the fibers 

ere rated as large (9-25 f-L). 

Various organs and fluids of C. irroratus have been 

analyzed for biochemical content. Cooke and Goldstone 

(1970), upon examining the pericardial organs for monoamines, found a green-fluorescing and a yellowfluorescing system ofaxons and terminals. 

Functional organization of the propus-dactylus organ 

consisted of paired neurons in one scolopidium that were 

ensitive to the same directional stimulus (Hartman 

1966; Hartman and Boettiger 1967). Certain movement 

cells showed position sensi ti vi ty. 

Blood sugar analysis by Telford (1968) revealed a 

mean glucose level of 8.1 mg/100 ml in animals collected 

off Maine during May and June. Reducing substances 

were 11.9/100 m!. No difference was found between sexes. 

Jeffries (1966) found a mean concentration of 2.11 mg 

glucose/100 ml serum and 2.41 mg phosphate/100 ml 

serum in the rock crab. 

A study to determine the characteristics of hemolymph upon infection by the bacterial pathogen Gaffkya 

homari, recently renamed Pediococcus homari (Section 

3.3.5), determined several hemolymph protein values: 

mean hemolymph serum protein 23.0 mg/ml ± 10.5; 

mean hemocyte values/mm3 X 104 were 2.24 ± 1.14, 

correlation coefficient (cells/serum protein) of 0.723; 

ratio of hemocytes (Lga:Sga:Ly or large granule amoebocytes: small granule amoebocytes: lymphocytes) of 

16:10:1; and a hemolymph pH of 7.38 ± 0.1 at 20°C 

(Stewart and Dingle 1968). 

Biochemical analyses of digestive gland enzymefJ in 

the rock crab (Hiltz and Lightle 1970) determined the 

mean activities of {3-glucuronidase and arylsulphatase as 

53 and 115 f-Lg phenol liberated/g powder per h, respectively. 

Carbohydrase analyses of C. irroratus tissue homogenates revealed a strong activity on the substrates glycogen and maltose, a moderate activity on amylose and 

amylopectin, and a very slight activity on trehalos~, raffinose, a-lactose, {3-lactose, cellobiose, and laminarm. No 

activity was recorded on sucrose, mannan, turanose, 

melezitose, melibiose, cellulose, fucoidin, lichenin, gaJactiI)., xylan, methyl glucoside, or innulin (Telford 

1970). 

Blood samples taken directly from the heart of male 

rock crabs were analyzed by Dean and Vernberg (1965) 

for the chromatographic presence or absence of blood 

carbohydrates. Of the carbohydrates tested, fl.laltotetraose, maltotriose, maltose, glucose, galactose, and a 

galactan derivative were present and mannose and 

fucose were absent. 

3 

2 DISTRIBUTION 

2.1 Total area 

Cancer irroratus inhabits the continental shelf and 

slope waters from Labrador to South Carolina (Rathbun 

1930; Squires 1966; Williams 1965; Nations 1975); Jeffries (1966) listed the southernmost limit as Florida while 

Carpenter4 has positively identified C. irroratus in the 

Straits of Florida. The crab typically occurs in shallow 

waters in its more northern habitats (Williams 1965; 

Templeman 1966), in deeper, sandy-bottom regions 

further south (MacKay 1943), and in bays and inlets in 

intermediate areas (Jeffries 1966). Most of these distributional patterns vary seasonally, especially south of 

Massachusetts and Rhode Island. 

2.2 Differential distribution 

2.21 Spawn, larvae, and juveniles 

Sastry and McCarthy (1973) found ovigerous females 

with eggs nearing hatch from late April (water column 

5°C) to early June (15°C at bottom, 19°C at surface) in 

Narragansett Bay. Other collections have found ovigerous females from late December through late August in 

Rhode Island waters (Bigford5). 

Larvae hatch from late spring throughout the summer 

months. In Canadian waters, Connolly (1923) and Scarratt and Lowe (1972) collected C. irroratus larvae between June and September. Fish (1925) collected larvae 

at Woods Hole from May to August. Hillman (1964) first 

found Cancer larvae in Narragansett Bay in late May 

while Frolander (1955) found larvae from April to late 

October in the same waters. Coastal New Jersey 

plankton surveys by Sage and Herman (1972) revealed C. 

irroratus larvae in late spring samples. In Delaware Bay, 

larvae were collected in April, May, and June (Deevey 

1960). Sandifer (1973) found C. irroratus zoeae (stages 1-

IV) in lower Chesapeake Bay from May to October, exluding August. 

Hillman (1964) first found larvae in Narragansett Bay 

plankton samples when the bottom-water temperature 

was 9.2°C and found them last when the surface waters 

reached 18.4 °C. Note that these data were collected prior 

to verification of the larval description (Section 3.22). 

These temperature limits are significantly lower than 

those reported for other decapod larvae within the bay 

(Hillman 1964). Water reached 9.2°C in late Mayor early June in Narragansett Bay. .. . 

Larval distributions in plankton collectlOns mdlCated 

that zoeae hatch offshore. This pattern of occurrence 

more seaward was observed by Sandifer (1972) in the 

Chesapeake Bay area and predicted by laboratory 

experiments by Bigford (1976, 1977). As development 

proceeds, larvae may be found nearer to shore. 

'R Carpenter formerly with the Virginia Institute of Marine Science, 

Glou'cester Poin~ , VA 23062, pers. commun., Jan. and June 1978. 

'T. E. Bigford, formerly with the U.S. Environmental ProtectIOn 

Agency, Narragansett, RI 02882. Unpubl. data. 
Juveniles appeared to migrate, or are carried by cur-

:ents, to shallow waters and the intertidal zone. Krouse 

1977) reported an abundance of small juveniles (5-40 

mm carapace width) buried in the pebble, rock, and shell 

:lebris of the shoreline in Maine. 

2.22 Adults 

Adult rock crabs are distributed in specific patterns 

with respect to depth, time of year, substrate, and water 

temperature. A complete, but dated, listing of the place 

Df capture, substrate, and depth for a series of collections 

tS given by Rathbun (1930). Most collection efforts have 

been concentrated in the summer months, thereby biastng annual collection data. 

Depths of occurrence vary with time of year and sex. 

Migrati()ns of each sex yield changing patterns of di tribution, particularly in coastal waters. In the northern 

part of its range the rock crab is found along the coast 

year-round; in the south, frequent shelfward migratIOns 

apparently occur that spread the population into deeper 

(> 170 m) waters in the summer months. Tagging studies 

would verify these migratIOns. 

In southern New England waters the rock crab has 

been collected at depths up to 170 m (Jones 1973; Reilly 

1975); surveys in more southern waters have revealed a 

tendency toward even deeper waters. Musick and 

McEachran (1972) found C. irroratus at 274 m off the 

Chesapeake Bight; Haefner (1976) collected rock crab in 

the Mid-Atlantic Bight region at depths to 751 m. 

Rathbun (1930) reported collecting several indiVIduals at 

592 m near North Carolina. 

Movements of rock crab populations were noted by 

several researchers. The southern trend, as observed by 

Jones (1973) in Rhode Island and Cerame-Vivas and 

Gray (1966) and Shotton (1973) in Virginian waters, is 

apparently for the crabs to migrate offshore into cooler 

water temperatures in the summer. Northern populations remain predominantly inshore throughout the year 

(Krouse 1972; Stasko see footnote 2). 

With respect to substrate, the rock crab is found primarily on sand-mud substrates south of Cape Cod (Jeffries 1966; Weiss 1970; Stewart 1972; Shotton 1973; Steimle and Stone 1973). Gulf of St. Lawrence's populations 

appear to be less selective of substrates in the summer, 

with crabs common on rock, gravel, sand, and mud 

(Stask06). Fall collections (Scarratt and Lowe 1972) indicate that these same Canadian crab populations may 

prefer rock outcroppings in cooler water temperatures. 

Interspecific competition affects distribution patterns, as 

discussed in Section 3.33. 

Distribution patterns, including migrations, are closely related to time of year and hence water temperatures. 

During the winter months, southern rock crabs tend to 

move inshore. In the 'Chesapeake Bay the shoreward migrations are initiated when water temperatures fall below 

15.5°C (usually late October or early November) (Shot-

'A. B. Stasko. 1976. Northumberland Strait Program: lobster and 

rock crab abundance in relation to environmental factors. Int. Counc. 

Explor. Sea, Doc. CM 1976/k:25, 13 p. 

4 

ton 1973). In Rhode Island waters the inshore movements also begin in mid-autumn (,Jones 1973; Bigford see 

footnote 5). 

2.3 Determinants of distribution changes 

Cancer Lrroratus i di tributed in specific patterns with 

respect to temperature, sallnity, light, gravity, pressure, 

ubstrate, depth, and carapace size. The relati ve effect of 

each factor varie with age and time of year. 

Zoeae and megalopae were found ( as try 1970; astry 

and McCarthy 1973) to urvive differentially in variou 

temperature-salinity regime depending upon the stage 

of development. Tables 1 and 2 show the trend in development and mortality toward an apparent optimum at 

15°C and everal alinite or 20°C and 25"1.. andifer 

(1973) collected zoeae in temperature- alinity range of 

13.00 -27.9°C and 23.31-32.03 Z., re pectively . Few larvae 

were collected above 25°C or below 25/ •• , reflectlng the 

optima hown III Table 1 and 2. 

Rock crab larvae !>how dIfferential survival in variou 

temperature regime. Re earch by a try (1976) hawed 

that both the mean temperature and the range affect urvival during larval development. Percent urvival of each 

larval tage wa higher under cycllc temperature; a 

range of 10° (lOo-20°C or 15"-25°C) re ulted III higher 

. urvival than cycle:. with 5°C range (Fig. 2. 3; Table 3). 

Thermal tolerance limit (LD. ,) for all five zoeal 

tage. hown by a try and Vargo (1977) were approxImately 2°C. -tage II and IV larvae exhIbited a lightly 

higher LDsu than the other three zoe a 1 tage; megalopae show a lethal temperature for 50c(; of the te t population at about 27°C, lightly below the zoeal limit. 

Adult rock crab are abundant in ~arragan ett Bay, 

R.I., where water temperature range from 1°C to about 

23°C annually (BIgford see footnote 5). Mid-Atlantic 

Bight populations have been reported in waters of 5.1°-

Table I.-Stage of development reached by larvae of Cancer 

irroratus in different combinations of temperature and 

salinity. I-V, zoeal stages; M = mega lops stage; C = crab 

stage. (From Sastry and McCarth) 1973.) 

Temp. 'ahmt:i 

(OC) 15 20 25 30 35 

10 I II ~1 ,,1 "I 

15 II C C C C 

20 I M .C M M 

25 I I I I I 

Table 2.-Percentage mortality of each stage of Cancer 

irroratus larvae reared in 30%. salinity at different temperatures. (From Sastry and McCarthy 1973.) 

Temperature 

Stage lOoC 15°C 20°C 25°C 

I 16.6 5.5 27.7 100.0 

II 13.8 3.7 5.5 

III 25.0 5.5 13.8 

IV 2.7 0 13.8 

V 0 3.7 11.1 

Megalops 41.6 20.3 27.9 
100r-------------------------------~ 

....J 

<i 

> 

~ 50 

::J 

(f) 

"" 

o Constant 

o 10°C cycle 

!Qg 5

u

C cycle 

10 15 20 10-

20 

15- 12.5- 17.5-

25 17 .5 22.5 

15 20 10-

20 

15- 12.5-

25 17.5 

15 20 10- 15- 12.5-

20 25 17.5 

TEMPERATURE. OC 

( a ) 

TEMPERATURE,OC 

(b) 

TEMPERATURE, ·C 

(c) 

Figure 2.-Percentage survival of Cancer irroratus larvae at constant and cycli c temperatures. (a) Hatch to megalops, (b) megalops 

to crab, (c) hatch to crab. (From Sastry 1976.) 

50r--------------------------------, 

(a) 

40 

20 

V> 

> 

~ 0 t---___ .....l:.-'-'-':I....-..L.:...:...:..L-LL..L.L-.lL.LL---D'-..:lI::L-___ -l 

IJ.J 

~ 

ff- 20 

z 

IJ.J 

~ 

~ 

(b) 

o .. ~ 0 ~---~~~~~~~L-~~~~L----~ 

> 

~ 50 

(c) 

40 

20 

1:-:-:-:1 Constant 

En 10°C cycle 

rs2SI 5°C cycle 

10 15 20 10- 15- 12.5- 17.5-

20 25 17.5 22.5 

TEMPERATURE, °c 

Figure 3.-Duration of larval development in Cancer irroratus at 

constant and cyclic temperatures. (a) Hatch to crab, (b) mega lops, 

(c) hatch to megalops. (From Sastry 1976.) 

5 

14.4 °C during June sampling (Haefner 1976). Near 

North Carolina, C. irroratus have been collected at temperatures up to 30°C in February and 32°C in May (F. J. 

Vern berg and W. B. Vern berg 1970). Maximum abundance, as reported by Haefner (1976) for the midAtlantic region in June, occurred at 8°-9.9°C, with density slightly lower between 10° and 13.9°C. 

MacKay (1943) hypothesized that the key factor affecting the distribution of Cancer crabs is temperature. 

Temperature governs distribution along the entire geographical range of the rock crab, imposing latitudinal 

and shore-to-shelf gradients. The crabs are rarely found 

north of the 4.4 °C mean surface water temperature isotherm or south of the 23.6°C isotherm. 

The influence of salinity is perhaps less severe than 

temperature . Zoeae, megalopae, and juveniles can survive in salinities ranging from 20 to 35%0 (Table 1). 

Synergistic effects of temperatures are important in determining the effects of salinity (Sastry and McCarthy 

1973). Adult and juvenile crabs are typically oceanic in 

Narragansett Bay and New England waters; salinity preference appears to be approximately 25-30%0, much like 

the larvae. (See section 3.35.) 

Sastry and Vargo (1977) studied possible seasonal variation in temperature-salinity responses. Results thus far 

indicated that larvae from winter hatches completed development in 30%0 at 10°C and in 25-35%0 at both 15° and 

20°C. Larvae hatching in the spring metamorphosed in 

25-35%0 at 10° and 20°C and in 20-35%0 at 15°C. Fallhatched zoeae completed development in salinities of 20-

35%0 at 15 °C and 25-35%0 at 20°C. Survival to the first 

crab stage was highest in spring hatches and lowest in 

winter hatches. Sastry and Vargo (1977) proposed that 

previous thermal history, plus the stage of egg development at collection, could influence these changing temperature-salinity limits. 

Laboratory studies on the responses of larval C. ir-
Table 3.-Survival of Cancer irroratus larvae a t constant and cyc lic tt'mp('ratur('~ . 

Zoeal stages I· V and megalops. (From Sastn I \l7t;.) 

Survival at 

constant temperatures 

Larval (C),', 

stage 10° 15° 20° 25° 

I 54 85 76 39 

II 37 78 68 17 

III 32 72 58 6 

IV 20 66 47 0 

V 15 60 31 0 

Megalops 0 40 17 0 

roratus to light, gravity, and pressure were undertaken 

by Bigford (1976, 1977, in press) in an attempt to de· 

termine when the transition from planktonic larvae to 

benthic crab occurred. Results showed an abrupt settling 

in stage V zoeae, shortly before the molt into megalopa, 

at a laboratory age of approximately 20 days. Absence of 

stage V zoeae and megalopae from the plankton was veri· 

fied by collections in Chesapeake Bay by Sandifer (1973). 

Rock crabs are abundant from nearshore to the con· 

tinental slope. In the Mid·Atlantic Bight, Haefner (1976) 

found highest densities of adults between 40 and 60 m on 

the continental shelf. Densities in Haefner's collection 

(June) were consistently higher in the shelf zone than 

either the slope or adjacent canyons. Withm these areas 

there are rather extensive migrations related to water 

temperature. In Narragansett Bay the population moves 

into shallow (about 6 m) waters during early autumn and 

returns to deeper waters (>20 m) during the spring 

(Jones 1973); Shotton (1973) observed a more wide· 

spread migration to depths of 274 m in the warmer 

months off Virginia. Sexes may migrate independently, 

as suggested by Jones (1973). 

Size has been correlated with population distributions 

in C. irroratus by Haefner (1976). Crabs ~50·mm cara· 

pace width ranged in depth from 10 to 150 m, with both 

males and females within this stratum. Intermediate· 

sized crabs (51-100 mm) were most abundant in the 

shelf-slope areas at 150-400 m. Large crabs (~101 mm) 

were mostly in nearshore waters at 20-60 m. 

The distribution studies of Haefner (1976) also included analysis of the relationship between crab size and 

water temperature. As stated by Haefner (1976): "Male 

crabs ~50 mm were not found in temperatures ~6°C, nor 

females ~50 mm at ~8°C. Otherwise this size group was 

equally abundant from 8 to 13.9°C. Crabs 51-100 mm in 

size had the broadest temperature range (4-13.9°C for 

males; 6-13.9°C for females), and were most abundant 

within the 8-9.9°C temperature stratum. The large male 

crabs (~101 mm) were taken within the 8-13.9°C temperature range." Note that these conclusions were based 

on collections in June only; data for September, November, and January are in preparation by Haefner'. 

·P. A. Haefner. Jr., Biology Department, Rochester Institute of Tech· 

nology, Rochester, NY 14623, pers. commun., Jan. 1978. 

88 

86 

84 

79 

78 

63 

6 

Survival at 

cyclic temperature. 

(e), " 

15°-25' 1:.1.5°·17· 17.5 ·~2 .. 'i 

87 82 76 

83 72 60 

7 66 40 

75 58 27 

71 49 20 

39 12 0 

2.4 HybridizatIOn 

2.41 Hybrids 

HybridizatIOn in C. Lrroratu ha n ot been 

demonstrated. The rather slight morphological differences between C Lrroratus and C boreali, the ympatri c 

pecie along the eastern U.S. coast, would make de· 

termination of hybridizatIOn on the basl of phy ical 

characters difficult (Jeffrie 1966). However, biochemical analy is of erum pho phate could reveal 

hybrids (Jeffne 1964, 1966). 

Cross· insemination tudie with the rock crab and 

everal decapod (LLbLnLa emargLnata, CallLnectes 

sapLdus, Uvalipes ocellatus, and Homarus amencanus) 

proved unsucce ful. The perm·egg interaction of C Lrroratus are highly pecific (Mowbray et al. 1970). 

3 BIO OMICS AND LIFE HI TORY 

3.1 Reproduction 

3.11 Sexuality 

Cancer Lrroratus, typical of brachyuran decapod , is 

dioecious. Slight sexual dimorphism occur . Haefner and 

Terretta (1971) diagrammed and Shotton (1973) 

analyzed the characteristic feature, abdominal morphometries, and growth (Fig. 4). Phillips (1939) mentioned 

that the mature female Cancer crab is u ually smaller 

than a mature male of the same age . Work on rock crabs 

from the Gulf of St. Lawrence (Stasko 1975), the Gulf of 

Maine (Krouse 1972), and the Mid-Atlantic Bight 

(Haefner 1976; Fig. 5) showed similar sex related ize dif· 

ferences. Mature females in Virginia have a longer carapace and deeper body than equivalent length males 

(Shotton 1973). No difference in cheliped size between 

the sexes has been reported. 

3.12 Maturity 

Sexual maturity is assumed to be that intermolt phase 

during which the adult crab can first mate successfully, 

as defined by Hartnoll (1969). In males, maturity is 

accompanied by the presence of fertile spermatozoa 

within the spermatophores of the vasa deferentia. In 

females, gonad maturation apparently does not occur until after copulation. Hence, the molt of puberty, where-
~ 9 

Figure 4.-Sexual dimorphism in abdomen shape in mature male 

and female Cancer irroratus. View is of the dorsal side when abdomen is extended. (From Haefner and Terretta 1971 ; Stasko text 

footnote 2.) 

by the body, organs, abdomen, and the appendages develop fully, is defined as the final stage in maturation of 

female crabs. Haefner (1976) showed a gradual development of the ovaries related to size. 

The stages of gonadal development for C. irroratus are 

summarized in Table 4 (Haefner 1976). Development of 

both testes and ovaries, plus all associated organs, was 

categorized for all crabs > 50-mm carapace width. 

Data of Krouse (1972), and also Scarratt and Lowe 

(1972), suggested a size at first maturity of 55-60 mm 

carapace width for females and 70 mm for males. Rhode 

Island population samples revealed egg-bearing females 

as small as 14 mm, with many collected in the 14-25 mm 

width ranges (Reilly 1975; Reilly and Saila 1978). 

Gonadal inspections of males and the presence of eggs on 

females from the coastal areas near Virginia suggested 

that individuals in southern populations may mature at 

about 30-mm carapace width (Shotton 1973; Terretta 

1973; see also Section 4.31). 

3.13 Mating 

The Cancridae exhibit several characteristic behavioral patterns during mating. Scarratt and Lowe 

(1972) suggested that courtship begins, probably initiated by the male, with the male clasping a female across 

her carapace. (The cradle carriage position is described 

by Terretta (1973).) This has also been observed in C. 

pagurus and C. magister (Hartnoll 1969). At this point 

the female molts, with mating following shortly thereafter. Typically, the clasping is followed by a postcopu7 

CARAPACE WIDTH (mm) 

2 5 50 75 100 125 

15 

10 

5 

o 

5 

10 

en 

CD 15 

<l: 

a:: 

U 20 

LL. 

0 

a:: 

UJ 

CD 10 

::!; 

::> 

z 5 MALE 

o 

5 FEMALE 

10 

15 ~-----r------.-------r------.-------r-; 

50 75 100 125 

CARAPACE WIDTH (mm) 

Figure 5.-Width frequency distributions of Cancer irroratus collected on two cruises: Blesk-30 September-1 2 October 1971, at 

48 stations from Cape Cod (lat. 41°09'N) to Cape Hatteras (lat. 

35°37'N) and Eastward-24-30 April 1973, off coast of North Carolina. Intermolt (C,-C" stage is represented by the blank area; 

soft and papershell (A,-B,) by the hatched area. Males frequencies 

a re above the line, females below. (From Haefner 1976.) 

Table 4.-Stages in gonadal development of Cancer irroratus. 

(From Haefner 1976.) 

Stage of 

development 

Undeveloped 

Very slight 

Slight 

Moderate 

Welldeveloped 

Very well 

Male Female 

Gonads not observed under 40X magnification 

Vasa deferentia thread- Ovary threadlike, delike, detectable with tectable with scope. 

scope. Colorless. Colorless. 

Thickened strands of Thickened ovary with 

vasa deferentia evi- naked eye. Colorless 

dent without scope. to white. 

Colorless. 

Testes and vasa deferentia equal approximately one-fourth 

volume of hepatopancreas. White. 

Volume of male organs 

subequal to that of 

hepatopancreas. 

White. 

Testes and vasa deferentia, the dominant 

internal organs. 

White. 

Ovary about one-half 

volume of hepatopancreas. White, tan 

to ligh t orange. 

Volume of ovary subequal to hepatopancreas. Light orange 

to orange. 

Ovary larger than hepatopancreas; eggs are 

obvIOUS. Orange 
latory embrace, during which the male protects the softshelled female. 

Cancer irroratus continues to molt past maturation. 

Therefore, copulation can occur several times in the 

crab's life, always in conjunction with a molt of the 

female. The time mating occurs is determined more by 

the condition of the female than the male, occurring only 

during the relatively short time the females are softshelled (Terretta 1973). 

3.14 Fertilization 

The entire process of mating in Cancer crabs and the 

other Brachyura is discussed in detail by Hartnoll (1969). 

The first two pairs of pi eo pods in male crabs are modified to act as penislike sperm transfer organs. While 

transferring the sperm, and throughout the mating sequence, the male grasps and protects the female. 

Because of the presence of a seminal receptacle in the 

female, it appears that fertilization is internal (Hartnoll 

1969). Egg-laying usually occurs within several days of 

mating. The delay is caused by the presence of a semen 

plug or seal on the receptacle opening (caused by deposition of semen during copulation) and by the maturation 

of the ovaries after mating. 

3.15 Gonads 

Most of the brachyuran crabs, including Cancer irroratus, within the subsection Brachygnatha have the 

same generalized internal anatomy (Barnes 1973; Terretta 1973). Both sexes have paired gonads. For the most 

part, the gonads lie within the thorax (Haefner see footnote 7), occasionally extending to the first few segments 

of the abdomen. Each branch of the testes and ovaries 

bears many diverticulae. 

The terminal portions of the gonads are adapted for 

mating and fertilization. In males, the end of the sperm 

duct is musculated for use an an ejaculatory organ. 

Usually the duct opens to the outside near the base of the 

coxa or at a joint of the coxa and sterna. In females, the 

terminal portions of the ovaries are modified into 

seminal receptacles which receive sperm from the male 

pleopods. 

The relationship between gonad development and carapace width, and gonad development and inter molt 

stage, are shown in Figure 6 and Table 5. Male crabs 

~101 mm had well-developed gonads, with smaller crabs 

showing comparatively less maturation. Gonads in females in the 80-100 mm range were developed but not 

ripened; small females were in early ovarian development (Haefner 1976). Many (52-82%) of the male crabs 

100 

75 

50 Undeveloped 

25 

0 

75 

50 Very Slioht 

25 ',- & 

..... 0 

z :il I.IJ 

u 

cr 

I.IJ 

11. 

I.IJ ~ 

Slioht cJ 

> 75 ..... 

<l: 50 -l 

::> 25 

Moderate //\\ Q 

..../ \ 

/" 

::E 

::> 0 u :il ~ " 

JI Well U 

'T~' 

~l Very Well 

I 

p 20 40 60 80 100 120 140 

CARAPACE WIDTH (mm) 

Figure 6.-Percentage occurrences of various stages of gonad development in relation to size of 131 male and 136 female Cancer irroratus captured during a June 1973 cruise in the Mid-Atlantic Bight 

region, that portion of the U.S. continental shelf ranging from the 

coast of New Jersey south to the coast of North Carolina. See Table 

4 for a detailed description of the stages of gonadal development. 

(From Haefner 1976). 

Table 5.-Relatio!lship of intermolt stage and gonad development in 267 Cancer irroratus collected during June in 

the Mid-Atlantic Bight. N = numbers of crabs; % r,N = percent of the total for each sex; C" C" etc. = molt stages 

(see Table 11 and Drach (1939) for explanation). (From Haefner 1976.) 

Male Female 

Gonad D,·D, D,-D, 

development "i:.N ~N Cl-C, (%N) Al-B, r,N %'i:.N Cl-C. (%N) Al-B, 

Undevelop'ed 6 4.6 16.7 16.7 66.6 7 5.3 14.1 0 85.9 

Very slight 27 20.6 14.8 3.7 81.5 26 19.1 7.6 11.5 80.9 

Slight 40 30.5 22.5 15.0 62.5 26 19.1 42.4 11.4 46.2 

Moderate 29 22.1 38.0 10.2 51.8 71 52.1 80.2 11.2 8.6 

Well 2:> 17.6 60.9 0 39.1 6 4.4 66.7 0 33.3 

Very well 6 4.6 83.3 0 16.7 0 

N 131 136 

8 
with only slight gonadal development had hard - hell 

characteri tic (Haefner 1976). 

permiogene i in the Cancridae, including C. Irroratu8, was t udied by Langreth (1969). Mature perm 

are aflagellate, con i ting primarily of a pherical acroorne surrounded by the nucleus with hort, radiating 

arms. Mitochondria are absent or degenerate in the 

mature sperm. Centrioles are present in the nucleolasm at the ba e of the acrosome. 

3.16 Spawning 

Krouse (1972) reported collecting newly berried and 

recently spent (egged-off) females periodically throughout the year in the Gulf of Maine. Ovigerous females 

were most abundant between February and May and 

again in November and December. Recently pent 

females were most common from June to August. In 

Rhode Island waters the spawning peaks are also February to May (Reilly 1975). Jones (1973) and Bigford (see 

footnote 5) collected egg-bearing females until late 

Augu t. 

Unripe, bright orange-red eggs occur from late fall until the temperature increases of late spring (Reilly 1975; 

Krouse 1972). The eggs darken to a brick red as summer 

approaches and development proceeds. A pale greybrown color typifies an ensuing hatch. 

3.17 Fecundity 

Reilly (1975) counted the number of eggs from 33 

ovigerous females (carapace widths 21-88 mm) and 

V 

IV 

II 

9 

derived a regre. ion equation 

log l no. 01 egg 

carapac \\Idth (mm) 

r - D.t! 

Egg count. ranged lrom 4.430 to 330, 

peclmen . 

3.2 Preadult phase 

:3.21 EmbryoDlc pha e 

I r th 

EmbryoDlc development oj C lrroratw pro eed .... llhm the egg. At hatching the larval' ar u uall) ull) d 

veloped stage I zoeae, although prezoeal tage ha b l'n 

ob erved (Blgfordee footnote .')). 

Eye pot and heartbeat are vi.ihle "e-.eral da) pnor 

to hatchmg (BIgford see footnote .')). 

3.22 Larval phase 

Cancer lrroratus typically ha b\e weal tage and nt' 

megalopa tage (Connolly 192:3, anditer 1973, a tr) 

and McCarthy 1973; 'a try 19(7) (hg, 7). Lan e In th 

first zoeal tage are characterized by \\ell-de\ I p d 

thoracic limb, long dor al and rostral ~pme. , and larg 

lateral eye. The abdomen and telson hcm the lYPI al 

egmentatlOn. As zoeal development proleI'd", the t8-

'Extraction of back·transtormed nata rna\ ,m I, bid 

champ and Ol,en (l9'jjl. 

III 

M 

:> 0", 
tion patterns on the appendages change and the pleopod 

buds grow (see summary in Table 6). 

Cancer spp. larvae have several morphological features 

that distinguish them from other southern New England 

decapods (Hillman 1964). Each abdominal segment 

bears one pair of small lateral spines; the telson is bifurcate, with 3 inner and 1 lateral spine per fork. Hillman 

further described the general characteristics of the five 

zoeal stages. Cancer spp. have a long backward curved 

dorsal spine and a straight rostrum of about equal 

length. The abdomen bears a pair of hooked spines on the 

second segment and a pair of smaller spines on segments 

3,4, and 5. The cornua of the tel son have a pair of dorsal 

and a pair of lateral spines. Three pairs of spines are on 

the lateral margin of the telson. A concave depression lies 

between the spines. 

3.23 Adolescent phases 

Little research has been done on juvenile rock crabs, 

i.e., those crabs that have developed beyond megalopa 

but are not yet sexually mature. Reilly (1975) calculated 

mortality rates for subadults on the basis of stomach content analysis of cod, Gadus callarias, and little skate, 

Raja erinacea. Results showed that juveniles inhabit 

both bay waters and saltwater ponds in the Narragansett Bay watershed. Krouse (1977) found juveniles concentrated in the rocky intertidal zones of Maine. 

Zooplankton surveys (e.g., Sandifer 1973, 1975) and 

laboratory experiments (Bigford 1976, 1977, in press) inferred that rock crab larvae settle out of the plankton 

outside the bay waters they inhabit as adults. Mass 

migrations or other passive movements to inshore 

adult populations apparently occurred in the juvenile 

stages. 

Young-of-the-year Cancer irroratus crabs are first 

found in collections in Rhode Island waters in July to 

October (Jones 1973). These juveniles are in the softshell condition. Haefner (see footnote 7) stated that the 

hardening of the exoskeleton takes at least 1 mo, usually 

longer in cold weather temperatures, in crabs >50-mm 

carapace width. 

3.3 Adult phase 

3.31 Longevity 

Reilly (1975) estimated juvenile and adult ages, instars, and carapace widths based on field collections in 

Rhode Island waters. Table 7 shows estimates in growth 

with respect to age and instars. On the basis of Reilly's 

age estimator, adult rock crabs live up to 8 yr. 

3.32 Hardiness 

Typical of most molting animals, the hard-shell crabs 

(stage C, with firm exoskeleton) are much more hardy 

than soft-shell (stages A and B, exoskeleton thin and 

flexible) crabs. Haefner and Terretta (1971) reported 

keeping hard-shelled C. irroratus alive for over a month 

in circulating seawater tanks. Adult male and female 

10 

Table G. - Diagnostic features of stages during larval development 

of Cancer irroratu8. (Part from Sastry 1977 and Bigford see text 

footnote 5.) 

Pre· Dorsal and rostral spines lacking; maxilliped nata tory hairs reo 

zoeae du ed; bifurcate telson not pointed and rather blunt, with 

stage I spi nes. 

Sl Dorsal and rostral spines present; eyes not stalked; maxtllipeds 

1 and 2 with 4 natatory hairs; each furca of telson with 3 setae 

on inner Side, mandible With one pOint. 

S[l Eyes stalked; maxilllpeds 1 and 2 with 6 natatory hairs; each 

furca of telson with 3 seta~ on inner side; mandible blunt, 

Without pOint. 

Sill Maxillipeds 1 and 2 With 8 nata tory hairs, each furca of telson 

with 4 setae on Inner side; postenor edge of carapace with 

4-6 hairs. 

' IV Maxtlllpeds 1 and 2 with 10 natatory hairs; each furca of telson 

With ,5 setae on inner side; sixth abdominal segment present, 

pleopod buds present 

SV Maxillipeds 1 and 2 With 12 natatory bairs; sixth abdominalsegment bilobed; pleopods developed; single palp on mandible. 

Table 7.-Estimated age (years) and corresponding instars and 

ca rapace widths (mm) for male and female Cancer irroratus. (From 

Reilly 1975.) 

Males Females 

Carapace Carapace 

Age Instar Width lnslar width 

1 IV 13.7 IV 13.7 

2 VIII 39.9 VIII 39.9 

3 X 65 .9 IX SO. 

4 XI 80.4 X 61.1 

5 XII 97.3 Xl 70.9 

6 XIII 116.9 XlI SO.1 

7 XIV 139.6 xm 88.9 

8 XIV 97.2 

rock crabs have been held over a year in flow-through 

tanks without molting (Bigford see footnote 5). 

3.33 Competitors 

The three primary competitors with C. irroratus in 

Rhode Island waters appear to be the jonah crab, Cancer 

borealis, the American lobster, Homarus americanus, 

and the green crab, Carcinus maenas. Jeffries (1966) 

pointed out the possible competitive exclusion of Cancer 

irroratus from coarse sediment bottoms in Narragansett 

Bay by H. americanus. Stasko (see footnote 6) reported a 

similar inverse abundance relationship between rock 

crabs and lobsters in Northumberland Strait. Competition and resource partitioning studies in the Bay 

(Fogarty 1976) have shown that C. irroratus inhabits 

solely fine-grained, sandy environments, and C. borealis 

occurs primarily on rocky terrain, but also on gravel; 

Carcinus maenas also was found by Fogarty to be only on 

sandy surfaces. Based on these field observations, Cancer 

irroratus would appear to compete with its sandy bottom 

cohabitant, Carcinus maenas. Laboratory experiments 

on rock, sand, mud, and gravel sediments have shown 

that the rock crab selects rock 62%, sand 23%, mud 8%, 

and gravel 6% (Fogarty 1976). However, in the presence 

of Cancer borealis, the preferred substrate was switched 

to 24% -rock, 52% sand, 13% mud, and 11% gravel. Apparently, the presence of C. borealis competitively ex-
cludes the rock crab from its preferred substrate. Carcinus maenas and Cancer irroratus pairings were not 

studied. 

The competitive resource could be shelter. Fogarty 

(1976) has shown that C. irroratus will utilize a laboratory shelter 100% of the time when no jonah crabs are 

present. With rock and jonah crabs both in the tank, C. 

irroratus achieved control of the protective shelter in 

only 28% of the cases, with 64% having C. borealis and 

the remainder shared by both species. This again confirms displacement of C. irroratus by C. borealis. 

As a result of the competitive pressures of C. borealis, 

the rock crab is found primarily on sandy substrates. 

This limitation appears to be by behavioral competition 

and not its physical attributes (Fogarty 1976). Interspecific agonistic encounters between the Cancer congeners show that C. borealis induces direct avoidance reactions in C. irroratus; the rock crab causes no such 

behavior in the jonah crab (Fogarty 1976). 

Rock crab survival on sandy substrates, including 

avoidance of competitors (Carcinus maenas) and predators, is enhanced by burial in the upper layers of sediment. As shown by Jeffries (1966), Cancer irroratus is better suited to extended locomotory efforts than C. borealis. 

Fogarty (1976) has shown a similar advantage for the 

rock crab in burial time; C. irroratus can completely bury 

itself in an average of 16.3 s, while C. borealis requires 

about 48.9 s. Slightly larger pereiopods may assist the 

rock crab in its burial activity. The complete sequence 

of burial is described by Fogarty for C. irroratus. 

These competitive pressures do not exist throughout 

the range of the rock crab. In the absence of either C. 

borealis and/or Homarus americanus, the rock crab is 

found in rocky areas. Examples of locations where C. irroratus inhabits its preferred niche are in portions of the 

Canadian Atlantic coast (Northumerland Strait) (Scarratt and Lowe 1973), in some coastal Virginian waters 

(Haefner and Terretta 1971), and in parts of Delaware 

Bay (Winget et al. 1974). 

A coefficient of association was calculated by Haefner 

(1976) for rock crabs collected in the Mid-Atlantic Bight. 

Contingency tables were used to compute Cole's (1949) 

coefficient of association (C7 ) for C. irroratus paired with 

C. borealis and Homarus americanus. Results showed a 

very close association (C7 = 1.000, P = 0.025, t = 4.427) 

between the two Cancer species in the Chesapeake Bight 

region during June and a negative association for October in the New York Bight (C7 = 0.483, P = -0.025, t = 

2.322). The rock crab was significantly associated with 

the lobster in June in the Chesapeake Bight (C7= 0.766, 

P = 0.025, t = 2.353), which was expected due to the 

positive association between lobster and jonah crabs. 

Stasko (see footnote 6) has shown a negative association 

between the rock crab and lobster in the Gulf of St. 

Lawrence during the summer. 

3.34 Predators 

Jeffries (1966) and Reilly (1975) mentioned the activity of predatory fish upon C. irroratus. Predation by 

cod, Gadus callarias, and little skates, Raja erinacea, on 

11 

the Rhode Island rock crab population has been used a 

an indicator of predation (Reilly 1975). Reilly showed 

that there was a tendency for skates to prey upon 

juveniles <20 mm wide more extensively than cod do. 

Other fish known to feed on rock crab juveniles and 

adults include smooth dogfish, Mustelus canis; red hake, 

Urophycis chuss; ocean pout, Macrozoarces americanus; longhorn sculpin, Myoxocephalus oC.todecimspinosus; toadfish, Opsanus tau; cunner, Tautogolabrus adspersus; tautog, Tautoga onitis; striped bass, 

Morone saxatilis; and goosefish, Lophius americanus 

(Field 1907; Bigelow and Schroeder 1953; Reilly 1975; 

Reilly and Saila 1978). 

Ennis (1973) reported that in Bonavista Bay, Newfoundland, C. irroratus and several other decapods make 

up a total of almost 50% of the stomach contents of 

Homarus americanus. The intensity of predation varied 

seasonally, reaching a minimum in midsummer. Ro-ck 

crabs also comprised about 28% of the stomach contents 

of lobster in Nova Scotia seaweed communities (Miller et 

al. 1971). 

Mention was made by Sastry (1971) that C. irroratus 

larvae are cannibalistic under laboratory conditions. For 

this reason individualized culture systems are frequently used. 

3.35 Parasites, diseases, injuries, and abnormalities 

Many of the common fouling organisms observed on 

adult rock crabs were identified by Haefner and Van 

Engel (1975) and Haefner (1976). As noted in Table 8, 

the fleshy ectoproct Alcyonidium is abundant on C. irroratus in waters <75 m deep. 

Sastry (1971) and Johnson et al. (1971) reported 

infestations of the bacterium Leucothrix mucor in both 

laboratory and field studies, primarily on egg masses. 

Use of penicillin G greatly depressed bacterial counts in 

the recirculating seawater systems used by Sastry (1971). 

Cornick and Stewart (1968) found a moderate pathogenic effect of the bacterium Gaffkya homari on C. irroratus. Gaffkya homari is the transmittor of gaffkemia, 

an often fatal bacterial disease of Homarus americanus. 

Note that the scientific name of Gaffkya homari was rejected in favor of Pediococcus homari (Editorial 

Secretary 1971). 

The most common injury observed in rock crabs is the 

loss of appendages. Trawl samples frequently reveal 

crabs minus chelipeds or pereiopods. This may be a 

direct result of the collection process. 

The occurrence of two immature albinistic specimens 

of C. irroratus was reported by Dexter (1968). However, 

albinism is rare in anthropods; these two individuals are 

the only recorded albino rock crabs. 

3.4 Nutrition and growth 

3.41 Feeding 

Cancer irroratus is mostly carnivorous, and cannibalistic to an extent. The degree of cannibalism appears to 
Table B.-Incidence a nd type of fouling or ga nisms obser ved on Cancer irroratus 

captured in June in the Mid-Atlantic Bight. See Table I I for a description of 

the molt stages. (From Haefner 1976.) 

Hard and 2eeler crabs Pa2ershell crabs 

Depth Total Fouled Fouling Total Fouled Fouling 

(m) no. ('0) organisms no. (%) organism 

10-20 5 40.0 Alcyonidium sp. 2 0.0 

20.0 Gastropod eggcase 

20-40 60 20.0 Alc),onidium sp. 51 3.9 A lcyonidium 

3.2 Octolasmis loweii 

1.6 Hydractinea sp . 

40-60 40 15.0 Alcyonidium sp. 29 0.0 

2.5 Octolasmis loweii 

5.0 Hydractinea sp. 

75-150 15 0.0 

150-400 15 0.0 

Total 133 20.0 

be density dependent. It may be that cannibalism is solely a laboratory phenomenon; Scarratt and Lowe (1972) 

reported that parts of rock crab shell were found in the 

stomach of only one rock crab collected in the field. 

Feeding is accomplished with the aid of both the chelipeds and pereiopods, which hold the food up to the 

mouthparts. Food is torn up by opposing movements of 

the mouthparts. 

3.42 Food 

Rock crabs held in the laboratory were fed combinations of chopped quahaug, Mercenaria mercenaria; blue 

mussel, Mytilus edulis; assorted fish; and thawed adult 

brine shrimp, Artemia salina (Bigford see footnote 5). 

Haefner and Van Engel (1975) offered squid, although 

only papershell (molt stages A2 and B1) crabs accepted it. 

No studies were conducted relating the nutritive value of 

these foods to the needs of the crabs. Gut content 

analyses (Table 9) revealed that pelecypods such as the 

mussel, plus other animal and plant tissues, are consumed by field populations of C. irroratus. 

3.43 Growth and morphometry 

In the laboratory, the duration of (;ompletion of the 

five zoeal and one megalopa stages varies depending on 

temperture cycles, salinity, culture conditions, and food . 

With a constant temperature regime, development proceeded fastest (37 to 58 days) to first crab stage at 15 °C 

and 30%. (Sastry 1970, 1971). The duration of zoeal development was usually shorter and megalopal development longer when larvae were reared in cyclic (5° or 

10°C range; 10°_25° minimum, maximum) temperatures 

at 30%, (Sastry 1976). 

Growth of C. irroratus adults has been studied by 

~hotton (1973), Reilly (1975), and Haefner and Van 

Engel (1975). Results from Shotton's morphometry 

tudies (Table 10) implied that length-width relationhip in the rock crab are linear. One exception was the 

curvilinear ratio of propodus length on carapace width in 

male ~30 mm (Table 10). Generally, the various body 

12 

28 0.0 

11 0.0 

121 1.6 

proportions showed an abrupt change at approximately 

30-mm carapace width. This was particularly true of abdomen width, an indicator of sex and maturity (see Sections 3.11 and 3.12). 

Krouse (1977) suggested that at carapace widths below 

60 mm both sexes have the same growth rate . One linear 

regression (see footnote 8), Y = 0.556 + 1.247X (where Y 

= postmolt carapace width and X = premolt carapace 

width), described the growth rates for crabs ranging in 

size from 9 to 48 mm. Beyond that size, changes due to 

sexual maturity complicated the growth relationship. 

Studies by several investigators have shown that male 

rock crabs are larger than females in carapace dimensions. Maximum carapace widths were 141 mm for males 

and 106 mm for females in Virginian waters (Shotton 

Table 9.-Analysis of stomach contents (number with each food, 

percent total, weight of food) of Cancer irroratus in t he Gulf of St. 

Lawrence, Canada. (Fr om Scarra tt a nd Lowe 1972.) 

6-30 June 1967 21 Sept.-5 Oct. 1967 

Item No. % g/kg No. '70 g/kg 

Total examined 202 28 

Empty 50 29.2 

Amorphous matter 71 35.1 1.6 23 82.1 2.2 

Liquid 36 17.8 1.0 10 35.7 0.9 

Polychaeta 39 19.3 1.0 5 17.8 0.3 

Shell fragments 31 15.3 0.4 5 17.8 0.1 

Sand 21 10.4 0.2 

Eelgrass (Zostera) 9 4.4 0.1 

Sea urchin (Strongylocentrotus) 8 4.0 <0.1 3 10.7 <0.1 

Mussel (Modiolus) 6 3.0 0.2 9 32.2 0.1 

Amphipoda 5 2.5 <0.1 3.6 <0.1 

Pelecypoda 4 2.0 0.1 3.6 <0.1 

Gastropoda 3 1.5 <OJ. 3.6 <0.1 

Porifera 3 1.5 0.1 

Rhodophyceae 3 1.5 <0.1 

Tunicata 3 1.5 <0.1 3.6 <0.1 

Cumacea 2 1.0 <0.1 

Asteroidea (Astenas) 2 1.0 <0.1 4 14.3 0.2 

Chiton 0.5 <0.1 2 7.1 <0.1 

Foraminifera 0.5 <0.1 

Isopoda 0.5 <0.1 

Turbellaria 3.6 <0.1 

Cancer irroratus 3.6 <0.1 
1973). Boothbay Harbor, Maine, populatIOns were al 0 

sexually dimorphic (Krouse 1972). Indust(itll trawl samples from Rhode Island revealed a maximum carapace 

width of 126 mm for males and 100 mm for females (Reilly 1975). Dlfferences in carapace length between the sexes 

are reflected in the regression equations shown in Table 10. 

The adult width-weight relationship has been calculated for crabs from Casco Bay and Boothbay Harbor 

by Krouse (1972)n from Narragansett Bay by Fogarty 

(1976), and from Chesapeake Bay by Haefner and Van 

Engel (1975). Krouse's calculations, based on wet 

weights taken to the nearest 10 g, yielded an exponential 

curve. The regression equations (see footnote 7) showed a 

slight difference between the two Maine sites: 

Boothbay Harborloglo weight -3.39 + 2.82 log lo carapace width 

Casco Bay10giG weight -3.60 + 2.94 10glO carapace width. 

Sexes were grouped during Krouse's analysis since there 

were no significant differences in regressions (see footnote 8) between males and females. Haefner and Van 

Engel also determined the width to weight relationship: 

loglo premolt weight 

log 10 postmolt weight 

-4.06 + 3.14 log premolt 

width 

-4.14 + 3.14 log postmolt 

width. 

Differences in regression equations reported by these 

researchers arose from both methodology and the conditions of the crabs. While Krouse (1972) recorded weights 

to the nearest 10 g, Haefner and Van Engel (1975) used 

O.l-g calibrations. Krouse also used a different method of 

determining carapace width than did Haefner and Van 

Engel. Scarratt and Lowe (1972) have also calculated 

width-weight regressions, but they used preserved crabs. 

6.0. ZI ZlI 

4.0. 

... 2.0. 

:r 

C> 

i;j 1.0. ~ 

)- 0..7 m: 

Q o. ~ 

... 

E 

.. 

.... "" 0' 60 Z:m: 

~ 40. 

2 .0. 

1.0 

0 .7 

o.~ 

Tab)" ) fI.-R(>~n·"lon' 01 hod, m! I urt>m nt fro 

udult ("nnr, r ;rrurlltu. In \ Ir Int I \\ h r (f rum 

\1l'a-url'ment 

Campacl' length, ( I.) 

nn compare wIdth (I \\ I 

Left cheliped propodu 

length (PLl on 

carapace width ((WI 

Body thickn"ss (BT) 

on carapace width ((\\'1 

Th,ckn"" (CT) on 

WIdth (CW) 

Width lew) on 

thickness leT) 

Ahdomen width (A\\) 

to carapace width « \\) 

!\I 

F' 

~1 

M 

F 

~1 

F 

i\I 

F 

~I 

f 

\1 

t 

:\1 

F 

.\1 

F 

;\1 

F 

mm 

( I 

( I. 

·30 l L 

L 

1'1. 

30 I L 

.J PI. 

~30 PL 

<30 r 

<30 II 

·30 ('1' 

·30 l T 

all (. r 

.1 l T 

all l \\ 

all ( \\ 

,,30 A\\ 

<30 \\ 

~JO \\ 

·30 \\ 

All other studies reported here utilized fre h cra) . 

Haefner and Van Engel presented a detailed dl cu I n 

of crab width to weight relationships. 

3.44 Metaboltsm 

Oxygen consumption rates III the lOeal and megalopa 

stages (Figure 8) were studied by astry and Mc arth 

(1973) and Sastry and Vargo (197,). ::-itag I LO ae, which 

are the most Illsen itive to temperature, how d a 

relati vely constant QlO of <2 in temperature ranglll 

from ;)0 to :lO°C. Second stage zoeae how dam r ed III 

crease III QIO between 5° and 15°(" ~lth a rna Imum <.: 

of6.26 As with stage I and II zoeae, the third La e lana 

zm 

MEGALOPS 

, iii iii iii I i Ir----r, -...,,--,.---,.., --., 

0 5 10 15 20 l5 0 5 10 15 20 25 0 5 10 20 2' 

TEMPERATURE ·C 

Figure .. -'tetaooli('-temperatuN' reponse ('une for tb the zocal nd one m 

of Cancer irrorotu . (From "'a,tn aod 1 rth, I 7 .) 

13 
exhibited depressed oxygen consumption above 20°C. 

The last two zoeal stages showed an increase in QIO between 10° and 15°C. Generally, these zoeal QIO values inferred a more stenothermal tendency in later stage larvae. At the optimal temperature range of 10°-15°C or 

15°-20°C, Sastry and McCarthy (1973) found a typical 

,QIO of about 1-2; one exception was the fifth zoeal stage, 

which had a QIO of 7 at 10°-15°C. 

The metabolic adaptation of adult rock crabs to temperature acclimation was studied by Jones (1973). Oxygen consumption of winter-collected crabs from Rhode 

Island increased for the first 3 wk of laboratory holding. 

During this period the consumption rate changed from 

0.84 /11 0 2/mg dry wt per h for field animals to 1.50 /11 

after 1 wk at 18°C and 0.90 /11 after 3 wk. This latter 

value appeared to be the acclimated oxygen consumption value for 18°C. 

Specific patterns of organ respiration varied according 

to the collection and holding temperatures (Figure 9). 

Acclimation to temperatures near the seasonal temperatures resulted in a linear regression line; acclimation to 

out-of-season temperatures caused a curvilinear response of hepatopancreas oxygen consumption to temperature. 

Metabolic rates, measured by oxygen consumption, of 

rock crabs collected m South Carolina waters revealed 

seasonal shifts and a tendency to decrease above 20°C 

A 

2Sr-------------------------------~ 

24 

z_ 

o ~ - ,C 

f-' 20. 0. - :2 l: ::>,., 

~ -0 1.6 

001 

UE 

Z ~ 1.2 

w O to-

~ .=. o..B 

o 

0..4 

C 

3'C ACCLIMATED WINTER CRABS 

S2"1. Co.~RELAT o.N 

10. 15 20 

TEMPERATURE ·c 25 30 

34r-----------------------------~ 

15-;:-

-,C 

f-' tl._ 

::;: ~ 

::> Ul:=-

2'0 

0 

U '" 

~ ~ON 

to-

>- :!. x-

° 

32 

2.8 

24 

2.0. 

1.6 

1.2 

o.S 

0..4 

3'C ACCLIMATED SUMMER CRASS 

S5% Co.RRELATlo.N II 

y, 2.79-0.0T7W -Ql0S T . QOO6 T2 

10. 15 20. 

TEMPERATURE ·c 25 30. 

(W. B. Vern berg and F. J. Vern berg 1970). Highest oxygen consumption, found at 10° and 15°C, was 53.73 and 

92.55 /11 0 2/h per g, respectively. 

3.45 Molting 

The molt tages of C Lrroratus have been categorized 

according to exo keleton firmness (Table 11). Molt times 

varied with geographical location, age, and ex. investigations by Krouse (1972) in the Gulf of Maine Ahowed 

that month of peak hedding varied for each sex. The 

percent male shedder was highest in February and 

March; female shedders were rna t common in eptember and October. In Virginia coa tal waters, the exe 

also showed different moltmg cycle; recently molted 

males outnumbered female m winter and pring trawl 

catche (S hotton 1973). 

Cancer Lrroratus populatIOn near the Mame coa t 

molt in late wmter or early fall, depending on the ex 

(Krou e 1972). Bo ton Harbor population molt between December and Apnl (Turner 1954). In ~arragansett BaJ , percentage of po tmolt rock crab mcrea e 

progre ively between December and April, fallmg off in 

May (Jane 1973). Jeffne (1966) claJmed that rna t 

hedding occur between May and June in • arragan ett 

Bay In Che apeake Bay moltmg occurs in January in 

both exes (Haefner and Terretta 1971); by ffild-FebruB 

2Sr---------------------------__ ~ 

24 

z 

0-

;: ~ 20 0._ 

::;: " ~ ~ 16 2'0 

0", 

U ~ 12 

.3 ON 

to_ 

X :!. o.S 0-

0.4 

o 

IS' C ACCL MATED WINTER CRASS 

94% Co.RREL A no.N 

~-O.X2W-O.011T.O.OO) T7 

10. 15 20. 

TEMPERATURE ·C 

25 30 

2Srl -----------------------------, 

24 IS' ACCLIMATED SUMMER CRASS J 

0.4 

S2'4 Co.RRELATIDN ,/ I 

/0 

0/ / Y=1.61.-0.0nW-0 06I.T 

10. 15 20. 

TEMPERATURE ·C 

25 30 

Figure 9.- Cancer irrDratus hepatDpancreas Dxygen cDnsumptiDn (Y) as related to. temperature (0(') fDr: A) 

3°e acclimated winter crabs, B) 18°e acclimated winter crabs, e) 3°e acclimated summer crabs, and D) 18' e 

acclimated summer crabs. W is dry weight (mg) Df 1 ml Df tissue separation. All data PDints are means Df 10 

replicates. (After Jones 1973.) 

14 
Table It.-Molt cycle stages of Cancer irroratu8. Modified from 

Drach (1939). (From Haefner and Van Engel 1975.) 

Condition 

Hard 

Early 

peeler 

Advanced 

peeler 

Early 

buster 

Buster 

Soft 

Early 

papershell 

Mid-papershell 

Late papershell 

Stage Description 

C,·C, Shell very firm, strong; fmger pressure on subbranchial area of carapace does not cause indentation or flexing of shell. No limb buds present 

at site of lost appendages. 

Do-D, Shell firm, but finger pressure along sub branchial 

ecdysial suture line reveals slight flexibility . 

Limb buds may be present. 

D, ·D3 Shell firm, but finger pressure along ecdysial 

suture line reveals marked flexibility without 

cracking the line. Limb buds may be present 

and may be well developed. 

0, Ecdysial suture cracks with light finger pressure . 

Limb buds when present usually well developed. 

D, Ecdysial suture visibly separated; separation 

measureable at posterior edge of carapace at 

its junction with the abdominal segments 1 and 

2. Limb buds, when present, usually well 

developed . 

A, Newly molted. Skeleton very soft. Still in process 

of water uptake. 

A, Exoskeleton leathery, pliable to the touch. 

B, Exoskeleton thin, brittle; dents under fmger 

pressure but returns to normal shell configuration when pressure is released ; merus and 

propodus oflegs bend without breaking. 

B, Exoskeleton brittle but thick; finger pressure 

may fracture shell; merus and pro pod us crack 

when bent; anterolateral spines hard. 

ary more than 90% of the crabs were papers hells (Terretta 1973). Early summer collections in the mid-Atlantic 

reveal that 67% of the crabs were in molt stages A1-B2, indicating a recent molt. Of the remaining crabs, 12% were 

preparing to molt (D2-D4) and only 12% were hard shell 

(C1-C4) or in the intermolt period (Haefner 1976). 

Detection of premolt signs was discussed by Haefner 

and Van Engel (1975). The best single characteristic to 

describe the different molt stages was shell rigidity, on 

which Table 11 is based. However, numerous secondary 

observations were recorded . Detachment of the 

epidermis and the formation of new setae on maxillae 

and maxillipeds marked the development of a new exoskeleton. These traits were visible at 15-20X magnification. No changes in color were observed to accompany 

the succession of intermolt stages preceded by the molt. 

A technique has been described by Haefner and Van 

Engel (1975), to determine proximity to molting by dislocating and removing the dactyl of a cheliped. If the 

break is clean and the new exoskeleton emerges undamaged, the crab is nearing a molt; rough breaks 

resulting in tom tissue are indicative of a hard-shell crab. 

Each molt is accompanied by several changes in body 

proportions, especially carapace width, carapace length, 

and weight. The changes are typically linear increases 

(Haefner and Van Engel 1975) of approximately 20-25C;o 

(Scarratt and Lowe 1972; Haefner and Van Engel 1975; 

Reilly 1975), decreasing slightly as size increases (Tables 

12, 13, 14). Size regressions (see footnote 8) between premolt and post molt size have been described by Haefner 

and Van Engel (1975) and Reilly (1975): 

Postmolt width (mm) 

Postmolt length (mm) 

Postmolt weight (g) 

3.93 + 1.16 premolt width 

(mm) for 125 males 

1.61 + 1.16 premolt length 

(mm) for 60 crabs sexes 

combined) 

- 5.33 + 163 premolt weight 

(g) for 57 males (28.7-141.6 

g; r2 = 0.9506). 

Further changes in weight occurred during the many 

molt stages. A 0.5-3% loss frOID initial weight was 

Table 12.-Average carapace widths (mm), absolute and precentage increments, and 

their ranges for 125 male Cancer irroratus. Pooled data for three seasons, 1970-73. 

(After Haefner and Van Engel 1975.) 

Premolt Mean carapace width Mean and % 

width N Premolt Postmolt increment 

51-60 4 58.15 74.03 15.88 27.25 

61-70 22 66.42 80.62 14.20 21.38 

71-80 40 75.23 91.16 15.93 21.18 

81-90 37 85.63 103.47 17.84 20.83 

91-100 18 95.29 113.96 18.67 19.59 

101-110 4 102.96 125.60 22.63 21.98 

Ranges 

Premolt 

width Increment 

57.6 59.0 10.5 19.0 

61.5 70.0 10.4 23.0 

71.0 80.6 11.6 21.6 

81.0 90.7 10.4 23.0 

92.0 100.3 17.0 27.1 

101.8 105.0 18.2 24.0 

Table 13.-Average carapace lengths (mm), absolute and preoental(e in<:rement . and 

their ranges for 43 male Canoer irroratus. Pooled data for thre.., ,ea un- Wio-i3. 

(After Haefner and Van Engel 1975.) 

Premolt Mean carapace length 

length N Premolt Postmolt 

31-'40 2 3 .70 +i.15 

41-50 15 45 .93 55. 9 

51-60 17 55.45 65.-

61-iO 10 64.51 'i6.60 

15 

:\!ean and 

merement 

7.45 19.10 

10.73 2313 

10.41 

1~.09 

__ }{.a~e, 

Premolt 

length /nerem t 

l- 5 399 

4! 1 50 

51 i 

626 

, 142 
Table 14.-Aver age weights (g), a bsolute and percentage increments, and their ranges 

for 57 male Cancer irroratus. Arranged according to carapace width (mm). Pooled data 

for three seasons. 1970-73. (After Haefner and Van Engel 1975.) 

Premolt 

Mean weight 

width N Premolt Postmolt 

51-60 3 30.1 54.6 

61-70 16 47.0 71.1 

71-80 22 69.4 106.3 

81-90 14 99.6 159.1 

91-100 2 138.7 220.2 

observed during the first 2-3 days premolt. When the ec-

·dysial sutures opened, the body weight may increase up 

to 90% due primarily to water uptake (Haefner and Van 

Engel 1975). Typically, the water content remained constant at approximately 65-70% during molt stages C4, Do, 

D2-Da, and D4 (identified in Table 12). During D4, water 

is absorbed until the percent content reaches 80-90% in 

stage AI' Stages A2, Bl> and B2 also exhibit this higher 

water content level. 

Comparisons of crab weights from various collections 

may necessitate some form of standardization for varying 

calcification rates. Richards and Richards (1965) described a decalcification technique for C. irroratus. 

Cancer irroratus, like all brachyurans, possess a series 

of neurosecretory complexes within their eyestalks that 

control the molting process. Removal of a portion of the 

eyestalk (Simione and Hoffman 1975) affects one of these 

endocrine organs (Y -organ) specifically. Resultant 

changes in the Y -organ include an increased rate of RNA 

synthesis and an increased cell volume. Both ofthese Yorgan changes occur immediately following partial eyestalk ablation and persist for 4 or 5 days thereafter. 

Larval diet studies have been undertaken by Bigford 

(see footnote 5). Measurements of zoeae reared on a diet 

of newly hatched brine shrimp, Artemia salina, are presented in Table 15. At these stages sexes could not be differentiated. 

Measurements of juvenile crabs collected intertidally 

are listed in Table 16. Predicted sizes based on regression equations and values from crabs reared in the 

laboratory are also presented. Note that the molt instars 

used by Krouse (1977) (Table 16) do not coincide with 

those used by Reilly (1975) (Table 7). The field carapace 

widths (of both Krouse and Reilly) are slightly larger 

than those of laboratory-reared animals. 

Table 15.-Cancer irroratus lar val carapace measurements (mean ± 

standard deviation, mm), based on a diet of newly hatched brine 

shrimp nauplii. Stages I-V = zoeae ; M = megalopae. (From 

Bigford see text footnote 5.) 

Larval Dorsal Carapace Carapace 

stage N Spine·height width length 

I 15 0.688±0.033 0.936±0.034 0.664±0.028 

II 15 0.702±0.036 0.951±0.048 0.691±0.032 

III 15 0.722±0.027 0.984±0.066 0.771±0.027 

IV 15 0.913±0.082 1.186±0.039 0.990±0.037 

V 15 1.140±0.098 1.450±0.050 1.360±0.049 

M 15 1.892±0.069 2.396±0.120 

Ranges 

Mean and % Premolt 

16 

increment weight Increment 

24.5 81.8 28.7 32.4 22.3 26.8 

24.1 52.0 35.7 58.8 14.5 38.1 

36.9 52.6 49.0 86.7 16.4 63.1 

59.5 59.3 89.2 120.5 31.7 74.1 

81.5 58.7 135.7 141.6 74.8 88.2 

3.5 Behavior 

3.51 Migrations and local movements 

Mass movements of C. irroratus adult populations 

have been recorded near Narragansett Bay and Chesapeake Bay. In Rhode Island, movements occurred primarily within the Narragansett Bay region (J ones 1973). 

Jones (1973) found a definite change in population center 

from inside the bay in the winter and early spring to outside the bay in late spring and summer. Similar movements were observed in coastal waters near Virginia and 

Chesapeake Bay (Shotton 1973)_ Mature crabs moved 

offshore late in the spring and returned to shallow waters 

the following winter. However, in Boston Harbor waters a 

tagging study found the adult crab population to be essentially nonmigratory (Turner 1953, 1954); Dean9 and 

'D. Dean (editor). 1972 . The University of Maine's coherent project 

Sea Grant program. Unpubl. manuscr., 25 p. University of Maine, 

Orono. 

Table 16.- Comparison of mean juvenile a nd adult Cancer irroratus 

carapace widths (mm) based on : fi eld collections and derived 

regressions (Column A; Krouse 1977), r egression values only (Column B; Krouse 1977), Krouse's regression values a nd Haefner's 

(text footnote 8) pr ojections beyond stage X (Column C), and Laboratory reared (Column D; Bigford text footnote 5). Krouse's regression 

equation (text footnote 8): Postmolt carapace width = 0.566 + 1.247 

premolt carapace width . 

A 

I-V: Actual 

measurements 

VI-XIII: 

regression 

Instar values 

I 2.6 

II 3.7 

III 4.6 

IV 5.9 

V 7.4 

VI 9.6 

VII 12.5 

VIII 16.2 

IX 20.8 

X 26.4 

Xl 33.5 

XII 42.4 

XIII 53.4 

XIV 

XV 

XVI 

XVII 

B 

Regression 

values (based 

on Stage I 

actual 

measurements) 

2.6 

3.8 

5.3 

7.2 

9.5 

12.4 

16.1 

20.6 

26.3 

33.3 

42.1 

53.0 

66.7 

C 

Projections 

ofcolumn B 

and 

lab reared 

N x 

N/A 42 .6 

53.3 

65.8 

80.2 

97.0 

ll6.4 

139.0 

D 

Lab reared 

N x 

5 2.4 

5 3.5 

4 4.4 

3 5.6 

2 7.2 

2 9.6 
Stasko (see footnote 2) reported that rock crab populations in Maine and Canadian waters remained inshore 

throughout the year. 

Cancer irroratus adult migrations show marked differences between sexes. Mostly, ovigerous females exhibit the seaward migration to the mouth of Narragansett Bay in June to October (Jones 1973). Males tend to 

remain in the shallow (20 m or less) regions of the inner 

bay. 

3.53 Responses to stimuli 

Effects of temperature shock on locomotion in adult 

rock crabs were investigated by Jeffries (1966). Increased 

activity, especially walking, was observed upon exposure 

to a +8°C shock from 6° to 14°C. If reversed, the -8°C 

shock decreased activity. In terms of locomotory activity 

the optimal temperatures were determined to be 14° _ 

18°C. 

Studies of the response of adult C. irroratus to 

hyposaline conditions suggest that rock crabs can withstand a wide range of salinities for a short time (McCluskeYlt) . Adults (sexes not differentiated) were found 

to be euryhaline, surviving in salinities ranging from 10 

to 20%. (Table 17) for 3 days at 50 _8°C. Crabs normally 

occur in waters with salinities up to 35% •. 

Hall (1973) studied behavioral responses of C. irroratus to changes in external salinities. Behavior was 

monitored in terms of dactyl chemoreception. 

4 POPULATION 

4.1 Structure 

4.11 Sex ratio 

Sex ratios appear to vary both by season and location. 

In Northumberland Strait, males outnumbered females 

by a ratio of 5.9:1 in summer collections (Stasko see footnote 6). Studies by Krouse (1972) revealed changes in sex 

ratios at various locations off the coast of Maine. Between 1968 and 1971 in Boothbay Harbor more females 

lOW. J. McCluskey. 1975. The affects of hyposaline shocks on two 

species of Cancer. Unpubl. manuscr., 15 p. Narragansett Marine 

Laboratory, University of Rhode Island, Narragansett, Rl 02882. 

Table l7.- Percent mortalities of Cancer irroratus adult, 

held at different salinities in the laboraton for 3 du\.,. 

(From McCluskey text footnote 10.) . . 

Salinity .\olortal- mor-

(%.) N lties taittle. 

20 69 l.j..j 

15 18 2 II 10 

10 24 7 29.10 

0 18 18 100.00 

were collected than males; there were more males than 

females in 1969 landings from Casco Bay. The overall 

percentages were 62% female in Boothbay Harbor and 

32% female in Casco Bay. These differences may be the 

result of population movements, which may be restricted to one sex (Jones 1973), and therefore cause 

landings to be mostly unisexual. Dean (see footnote 9) reported a predominantly male sex ratio in other Maine 

waters. 

Rock crab populations in the Gulf of St. Lawrence 

showed some seasonal variations in sex ratio (Scarratt 

and Lowe 1972). Females outnumbered males all year, 

but the ratio varied from 1.31: 1 in the spring to 1.47: 1 in 

the fall. . 

Changes in the sex ratio of C. irroratus were also 

reported in Narragansett Bay (Jones 1973). The percentage of females in the populations at sampling sites 

near the mouth of the bay was generally lowest in February, March, and April. During this time the females were 

ovigerous and had moved into shallower waters on their 

way to their summer habitats in deeper water (Jones 

1973). 

Haefner (1976), studying rock crabs in the MidAtlantic Bight, fpund the male:female sex ratIO for 

adults to range from 1.0:1.4 to 1.9.1 (Table 18)_ In all 

water depth strata, except 20-40 m, this male dominance was significantly different frum 1: 1. The size clas 

51-100 mm had ratios of 1.7:1 on the continental slope at 

150-700 m to 4.6 and 4.9:1 at 75-150 m in canyons and on 

slopes. Sex ratios in these data seemed dependent on carapace size, collection depth and location_ In Maine, the 

sex ratio of juveniles below 40-mm carapace width is 1:1 

(Krouse 1977), and in the Delaware Bay, the male:female 

sex ratio was approximately 12:1 (Winget et al. 1974). 

Shotion (1973) reported a preponderance of males 10 

the coastal waters of Virginia. In crab pot catches the 

Table IS.-Sex ratios, by area and depth (ro), for Cancer irroratus captured in June 1973 in the Mid-Atlantic Bight. LargE'r 

than expected deviations from the 1: 1 ratio are labelled significant (sig) in the chi-square column. The ns denotes not significant. 

P level not given by author. (From Haefner 1976.) 

<50 mm width 51-100 mm width All crabs 

Area Depth Male Female Ratio Chi' Male Female Ratio Chi' Male Female RatIO ern 

Shelf 10-20 62 54 1.3:1 ns 3 3 1:1 ns 65 57 1.:!·1 

20-40 95 101 1:1.1 ns 28 86 1:3.1 sig 132 1 7 1 1 4 

40-60 96 60 1.6:1 sig 60 54 1.1:1 ns 159 114 1 4 I 

Slope 75-150 77 57 1.4:1 ns 50 11 4.6:1 sig lr 19'1 

150-400 0 2 0:2 ns 45 27 1. 7:1 sig 49 .?9 • - I 

Canyon 75-150 53 57 1:1.1 ns 44 9 4.9:1 Slg 97 66 • b I 

150-400 1:1 ns 30 19 1.6:1 ns 33 .!O 1 - 1 os 

17 
male:female ratio ranged from 4.6:1 to 111.7:1. Trawl 

catch data ranged from 0.6:1 to 12.5:1, with only the 0.6:1 

station reporting more females than males. 

4.12 Age composition 

The mean age composition of any particular field collection is especially dependent upon sample location and 

time of year (Jones 1973). These factors relate to population migrations and changing sex ratios. 

Fishing efIorts tend to concentrate on larger males 

(Scarratt and Lowe 1972). This pressure could alter the 

age composition by removing the larger and older males, 

resulting in a younger age structure. 

4.13 Size composition 

Krouse's (1972) studies in the Gulf of Maine howed 

hat male rock crabs dominate the carapace width cla!-1-

ses over 90 mm. At Boothbay Harbor the mean female 

and male carapace widths were 81.7 and 92.4 mm, while 

at Casco Bay the values were 77.1 and 107.0. 

Industrial trawl samples m Rhode Island coastal water 

revealed mean carapace Widths of 57 .3-1O~.9 mm for 

males and 597-79.5 mm for females (Reill . 1975). Larger 

sample means coincided mostly with the spnng month. 

and more seaward sample stations. 

Size frequency distributions of juvenile and adult 

crabs in Delaware Bay (Winget et a1. 1974) indicate a bimodal or polymodal distributIOn (Fig. 10). Thi relationship presumably changes m response to factor~ uch a. 

year class strength and mortality. 

It should be noted that collecting gear, i e., trawls and 

pots, may be size selective. Carapace measurement 

could be skewed in favor of some size classes by variou 

trawl nets or pot entrance and escape hole sizes. 

60 

50 

40 

>- U 

Z 

w 

:::> 30 

0 

W 

a:: 

LL 

20 

10 

0 

r---

r--

r- - - .--

~ 

, 

r-- - .--

-

r 

2.0- 29 4.0-49 6.0 - 69 80 -e.9 100-109 120-12.9 

30-3.9 50-59 7.0-79 9.0-99 11.0-1\9 13CH39 

SIZE: WIDTH OF C IRRORATUS IN eM . 

Figure 10.-Carapace width size frequencies of Cancer irroratus 

collected with crab pots in Delaware Bay from November-April 

1969-70. (From Winget et aJ. 1974.) 

18 

4.2 Abundance and den!lity 

4.22 Change in abundance 

Larval Htages of C. irroratus were most abundant in 

the (:ulf of St. Lawrenc(' from AUguBt to 'eptember 

(Scarratt and Lowe 1972). The numb('rs of larvae varied 

tremendously each year, with the highe t abundance 

usually occumng III late ummer. In Rhode 1.Iand 

waters, larvae occurr('d from lale May to early September, with 1.1 peak in mid ummer (Hillman 1964). forr). 

lander (J 9!)5), III plankton collectirJll. at two tati(JllI! in 

arragansett Hay, found larvae pre ent from April to 

late October. with peak abundance in .June and early ,July. 

Hi~he t !Jbundance of ('ancer irroratu adult in the 

C08. tal wfltefll of Vir~inia occurred in .. ebruary, March, 

!Jnd April, when in hllre wat r were colde t hotton 

1873), Sampling trawl in I arragan ett Hay netted mr t 

crab hetween. '"vernhf!r and :-"larch, which al J corre pond J to tim of l(Jwe t t mperature . In warmer 

munth th 1 rra~lIn ett Hay r "k crab pulation preurnably muv d award to are 0 lower temp rature 

Big ord e footnot.e 5). 

4 23 verage d n ity 

l'iankt(Jn tudic In I arragan tt Hay etween:-" a) 

and I e ember 1 1 revealed a mean den~ity 0 2. 

oncer _ pp (' Irroratu and ( boreall) larvae/m • 

with 8 ran/!e of -1 larvae/m, dep ndmg on 10 atlOn 

within the bay (Hillman 1964). 

'canatt and Lowe 1972) calculated the average 

tancltng . tOt k (If adult r k crab. in Kouchlbou~ac 

Bay, anada, to be 3., glm on rocky ub, trate and 1.3-

2.2 g/ml on sand and bedrock. Adult den itie were urveyed from a . ubm r'ihle by Caddy (1970) in the l 'orthumberland , trait III Canada On the ba i" of three dive 

the den. ity wa' O.Ul adult /m2• Fogarty (l97f) found a 

mean den Ity of 2.1 crab./5 m (OAlm<) In hi. diving 

quadrat in. 'arragan ett Bay water. 

43 • 'atality and recruitment 

4.31 Reproduction rates. 

Rock crab typically mate at the on et of the female 

postmolt (AI' A!. BI, or Bt ) period while the female is still 

soft (Terretta 1973). The minimum carapace width at 

which mating can occur, and the reproduction rate 

thereafter, have not been fully elucidated. Reilly (19,5), 

Reilly and Saila (1978), and Bigford II reported the occurrence of ovigerous females as small as 14-mm carapace 

width. Females may produce more than one egg mass 

from one copulation by storing the spermatophores. 

liT. E. Bigford. 1975 Occurrence of an unusually small oVigerous 

rock crab, Cancer Irroratus. in ;\Iarragansett Bay. L'npubl. manuscr., 4 

p. U.S. Environmental Protection Agency. Narragansett, Rl 02882. 
4.32 Factors affecting reproduction 

The close relationship between molting and mating infers that variables affecting one could influence the 

other. Most molts occur in the fall, with reproduction occurring in the fall, winter, and spring months. Egg masses are carried until the larvae hatch; temperature controls the length of embryonic development. For example, 

an unusually warm week in April 1976 resulted in an 

abrupt bottom water temperature increase in Narragansett Bay from 6.5° to 10.0°C in 1 wk. Shortly thereafter, 

all females collected in the bay lacked eggs but showed 

evidence of recent hatches (Bigford see footnote 5). This 

unusually early hatch seemed correlated with the temperatures in previous weeks. 

4.33 Recruitment 

Ovigerous rock crabs tend to migrate offshore prior to 

hatching (Jones 1973; Sandifer 1975). The larvae are 

therefore most abundant offshore near the hatching 

grounds. Recruitment back into the bay waters (e.g., 

Narragansett and Chesapeake) is apparently either by 

chance in the zoeal stages or by migration in the megalopa and juvenile crab stages (Sandifer 1975), with the 

latter method most probable on the basis of laboratory 

experiments (Bigford 1976; Bigford in press). 

4.4 Mortality 

4.41 Mortality rates 

Estimates of adult mortality were made by Reilly 

(1975) using the rate of total instantaneous mortality, Z. 

This relationship is based on the commercial catch curve 

and year classes, with the restriction that the latter do 

not vary significantly from year to year. In the male 

population of Narragansett Bay, the year classes did vary 

and an estimate of mortality was not possible. Calculations of Z for females revealed a change in mortality as 

the carapace size increased. Total annual mortalities for 

a sample collected in April 1974 were 54% for females 

<82.5 mm and 93% for crabs >82.5 mm. A May 1975 

sample gave 60% for crabs <86.5 mm and 94% for larger 

crabs. 

Field collections of juvenile ( <40 mm) C. irroratus and 

an analysis for annual natural mortality gave juvenile 

mortalities of 94% and 64% for two samples (Reilly 1975). 

The method involved stomach content analysis of Raja 

erinacea and Gadus callarias. Analysis of cod stomachs 

revealed mortalities of 59-8400 for juvenile crabs. 

When categorized by estimated age, mortalities calculated by Reilly (1975) were 75-85% for the second year 

and 65-8000 for the third year. With increased size, 

predation by fish became less important compared to 

fishing mortalities. 

4.42 Factors causing or affecting mortality 

Many of the predators, competitors, parasites, dis19 

eases, and injuries responsible for field and laboratory 

mortalities are discussed in Sections 3.33,3.34, and 3.35. 

Laboratory studies by Sastry (1970, 1976) indicated 

high mortalities in rock crab larvae reared under Ie 

than optimal conditions of temperature and salinity. Effects of temperature were especially lethal. Salimty may 

alter oxygen consumption (Hanlon 1958) and survival. 

Attempts to culture larvae on a variety of laboratory 

diets indicated that the ciliate Euplotes uannus could be 

responsible for rapid mortalities (Bigford see footnote 5). 

This ciliate was added to the culture as a food organism 

but does occur naturally in seawater systems. 

Cornick and Stewart (1968) reported high mortalities 

of adults in high density holding systems. Cannibalism is 

a frequent problem in holding systems for larvae and 

adults. 

4.5 Dynamics of population 

See Sections 2.21, 2.22, and 3.51 for discussions of 

population dynamics. 

4.6 The population in the ecosystem 

Jeffries (1966) described C. irroratus as being an open 

sand dweller in Narragansett Bay; the congeneric C. borealis inhabits the rockier areas. Absence of the rock crab 

from coarse sediment types (Steimle and Stone 1973) IS 

peculiar considering its common name. Jeffries (1966) 

and Fogarty (1976), as discussed in Section 3.33, suggested that C. borealis, Carcinus maenas, and Homarus 

americanus may be competing for sediment space and 

type with the rock crab. Juvenile rock crabs outnumber 

lobsters in both rocky and boulder-strewn areas off 

Canada (Scarratt and Lowe 1972). Tendencies for the 

rock crab to bury in sand and lobsters to excavate burrows may permit limited coexistence without competition. 

Fogarty (1976) studied Cancer irroratus in its own 

niche and in the ecosystem, based on both extensive diving surveys in Narragansett Bay and laboratory experiments. Niche breadth calculations, based on Levins' 

(1968) formulation, revealed that C. irroratus has a 

highly specialized pattern of resource use; the niche 

breadth value was 1.00, indictive of the fact that all rock 

crabs collected in Narragansett Bay were found on a 

sandy substrate. The role of the rock crab in the community matrix was calculated from the probability of occurrence of the rock crab and its decapod cohabitant 

(Cancer borealis, Homarus americanus, and Carcinus 

maenas) on rock, mud gravel, or mud substrate . Matnx 

values showed an extensive overlap of C. irroratWi with 

C. maenas, but not with H. amencanus or C. boreall.S 

Adult rock crabs have been ob en.ed to inhabit the upper regions of mantis shrimp, quzlia empusa. tunnel 

and abandoned lobster burrows In • 'arragan ett Bay 

(McCluskey!.!). 

•. \\ J. ;\lcClu key, :-\arragan~ett ;\!anne Laboraw~ l m~e t 

Rhode I land . :-\arragansett. RI O:! ~. pel>' commun J.Ine 19--
5 EXPLOITATIO~· 

5.1 Fishing equipment 

5.11 Gear for capture 

Crab of all species are commonly collected by various 

nets and trap. Bottom trawls. with either otter or 

German nets, and dredges are towed from fishing vessels; 

traps resemble lob ter pots, with specific designs highly 

variable (Bigford see footnote 5; Turner 1953, 1954). 

Typically. the pots are semicylindrical and 0.6·1.3 m 

long. Entrances may be constructed so as to eliminate 

certain size ranges. In Canada, various types of 

cylindrical, rectangular, or conical and metal or plastic 

trap have been tried (Caddy et a1. 1974). Shotton (1973) 

ment' ned that rock crabs are often attracted to Vir· 

ginia sea bass pots where trapped fish serve as bait. 

'tasko (1975) researched relative efficiencies of various trap material, entrance shapes, and entrance sizes. 

A long rectangular opening of 44.5 mm wide permitted 

crabs to enter while preventing passage to most legal-

,Ized lob ters. :\lodified lobster pots with the entrance on 

top fished exclusively for crabs. A study by Stasko and 

(,raham on seven trap types revealed that wooden traps 

Wlth a 5·cm metal entrance on top caught the most 

crab . The 5 cm by 27.5-62.5 cm metal entrance eliminate lob, ters, while a wooden trap caught more crabs 

than any metal trap. In Massachusetts, rock crabs are 

caught primarily by means of pots (Turner 1954). Most 

pot u ed commercially in Massachusetts waters are 

rectangular, about 0.3 m high, 0.6 m wide, and 1 m long. 

Oak is usually used for framework and heavy netting for 

the funnellike entrances. This crab trap differs from the 

lob ter pot in that the twine funnels are shaped to meet 

the contours of the crab and, secondly, small holes are 

dnlled in the framework to permit escape of juvenile 

crab, (1 urner 1954). A detailed description of the fishing 

gear and it manufacture is given by Marchant and 

Holmsen (1975). Hipkins (1972) described crab pots used 

in the Dungeness crab. Cancer magister, fishery on the 

west coast 01 • 'orth America. 

Man) bait are used depending upon cost and availablht}' In general. fresh bait is cheaper than the frozen 

or alted vanetie". Common baits are fish processing 

\ at, unwanted tish caught by trawls (skates, ocean 

put, ea robms), and industrial fish (menhaden, hernng, flatfi h, and mal'kerel) (I\Iarchant and Holmsen 

71)) 

B It hsh I U uall placed in bag' and hung in the pot. 

ppro 1m tel 1-2 Kg of fish is placed in each "purse" for 

III h re fl hmg, 2-1 kg are used for offshore grounds. 

I) 12 Buat' 

B '" and arragansett Bay area fisher19-0 PrehmlfllU) report on rock 

manu cr ~ p Fbhene. and :-.1arine 

ndre .... ' e .... Brun, .... lck. Canada, 

20 

men catch most crabs incidentally while trawling, dredging, or pot trapping for another species. In Canadian 

waters, a majority of the crabs are caught in lobster pots 

(Stasko see footnote 2). Lobster and trawler boats used in 

such operations are typically wooden, open, and 4-14 m 

long, with offshore vessels larger than inshore vessels. 

Offshore fishing vessels are usually equipped with onboard refrigeration systems. Holding tanks are maintained at or near bottom temperatures and are well 

aerated. 

5.2 Fishing areas 

5.21 General geographic distribution 

Rock crab populations are large enough to support a 

commercial fishery from the Chesapeake Bay region 

north to the Canadian provinces. Continental shelf populations both nearshore and in deeper waters have been 

harvested. 

5.22 Geographic ranges 

The first commercial fishery for rock crabs began in 

Massachusetts about 1900 (Turner 1953; Wilder 1966z. 

Shortly thereafter the fishery moved into the other New 

England states, Canada, and the Chesapeake region. 

Small canning operations began in Prince Edward Island 

and New Brunswick (Caddy et a1. 1974); fresh crab 

markets developed in Massachusetts (Turner 1953), 

Maine (Wilder 1966), and the middle Atlantic (Haefner 

et a1. 1973). 

Several areas appear to have the potential for commer· 

cial exploitation. In Canadian waters, Northumberland 

Strait and other nearshore waters are promising (Scarratt and Lowe 1972). Up to 97% of the total catch in some 

Canadian waters at some times of the year exceeded th 

arbitrary minimum market size of 89-mm carapac 

width (Scarratt and Lowe 1972). Southern New England 

and mid-Atlantic waters, where crabs migrate seasonally, may have commercially productive populations in offshore and onshore waters, depending on the season. 

5.23 Depth ranges 

As stated above, populations in shallow «50 m) 

waters may prove most valuable in the northern range 0 

the rock crab. In more southern areas, crabs may b 

fished seasonally in coastal bays (Narragansett an 

Chesapeake) or on the continental shelf. 

5.24 Conditions of the grounds 

Since the crab industry is still growing, all ground 

how large standing stocks of crabs. Due to the lack 0 

populations studies there are no reliable bases for esti· 

mating stocks or potential yields (Caddy et a1. 1974). 

Small surveys and recent catches in the crab fishery in 

Canada reveal that the sustained yield of the southern 

Gulf of t. Lawrence region could be 1.3-2.3 million kg 

annually mailer commercial stocks exist in the north-
ern Gulf area, off Newfoundland and off Nova Scotia 

(Caddy et a1. 1974). 

5.3 Fishing seasons 

5.31 General pattern of season(s) 

Cancer irroratus typically molts between December 

and May in southern populations and from December to 

as late as October in northern ranges. Due to the reduced 

meat yield of newly molted crabs, fishermen attempt to 

avoid fishing during peak periods of molting. This constraint limits the primary fishing seasons to the late 

spring, summer, and fall months (Turner 1953; Caddy et 

a1. 1974). 

5.32 Dates of beginning, peak, and end of 

season(s) 

Collections by Krouse (1972) at Boothbay Harbor, 

Maine, indicated peak abundance of C. irroratus in July, 

Augustn and September. These crabs would be marketable size with high meat to wet weight ratios. Throughout the remainder of the year, C. irroratus was less abundant in Boothbay Harbor than during these months. 

This apparent decrease in abundance could be attributed to the fact that crabs are much less active during the 

winter months than at other times (Stasko see footnote 

6). Peak abundance in Northumberland Strait, Canada, 

occurs when waters exceed 10°C. 

In Rhode Island waters, a similar peak in abundance 

occurred (Jones 1973). Trawl catches peaked in late summer offshore and in cooler months nearshore (see Section 

4.22). Weather permitting, harvesting may last 12 mo in 

Rhode Island and about 7-8 mo in Maine. Molting of 

crabs could restrict these fishing seasons. See Section 6.12. 

5.4 Fishing operations and results 

5.41 Effort and intensity 

Because lobsters are the primary target of pot fisheries, it can be assumed that rock crabs are caught with little extra physical effort. However, additional capital is 

needed to store the crabs onboard and to replace bait 

typically used in landing lobsters. 

Marchant and Holmsen (1975) calculated the feasibility of harvesting rock crabs. They concluded that the 

additional effort would generally result in a significant 

increase in income. At the 1974 prices, a full-time offshore lobsterman with an average business could eam 

$3,OOO-$16,OOO/yr from crabs alone. 

Rees (1963) suggested that the rock crab meat ranks 

high in flavor and should be utilized commercially. According to Haefner et a1. (1973), newly molted "peeler" 

crabs appeared to have potential as a commercial 

resource. Catches of these soft-shell crabs are particularly high in December and early January in the Chesapeake Bay area, where the resource may be exploited 

Soon. Northern Atlantic populations could also be exploited. 

21 

The economic returns to the fishermen depend upon 

the efficiency of his operation (Van Engel and Haefner 

1975). Crabs should be eaten the same day they are dre -

sed. Meat discoloration that affects marketability may 

occur during dressing (Van Engel and Haefner 1975). 

Production of minced rock crab meat involves eparation of shell fragments from the meat. Sims and Anderson (1976) devised a chemical method for calculating the 

amount of shell particles in the meat. In good crab meat, 

the concentration of shell particles remaining on a 20-

mesh sieve should be <0.3"0; particles remaining on a 50-

mesh sieve should not exceed 1.05%; and total shell contents should not exceed 1.25"0, based on a dry weight 

(Sims and Anderson 1976). Haefner et a1. (1973) di -

cussed a processing plant operation for commercial purposes. 

Ex-vessel landing prices are highly variable. In 1965, 

cans of prepared crab meat retailed for $1.50-$l. 79/kg 

(Wilder 1966). By 1967, prices for live crabs were 11-

24.4¢/kg in Rhode Island (Gates et a1. 1974); Canadian 

landing prices for inshore and offshore crabs from Rhode 

Island were 32¢ and 55¢/kg by 1974 (Marchant and 

Holmsen 1975). 

Meat yields from whole boiled crabs were calculated to 

be 21% of the live weight (Wilder 1966). However, considering that some useful parts of the crab are not 

utilized, the present commercial yield may be closer to 

10% (Wilder 1966). Table 19 summarizes the changes in 

meat yield over the course of the fishing season. Carbonneau (1965a, b), in addition to Wilder, discussed the 

potential of the species as a source of crabmeat. 

Table 19.-Catch data and meat yields (kg) from the Boston Harbor 

Cancer irroratus population. Traps used are described in Section 

5.11. (From Turner 1954.) 

Daily catch Crabs per Average meat yield of 

Month per trap kg meat _ daily_catch per trap 

Apr. ' 125-150 77-84 2 

May 50-75 42-46 About 1 

June 35-50 42-46 About 1 

July 35-50 '57 nder 1 

Aug. 20-40 '66 About 0 5 

Sept. 20-40 '66 About 0 5 

Oct. 20-40 '73 Under 05 

Nov. 30-50 88 About 0 5 

'Experimental fishing. 

'Increase in small crabs in catch. 

5.42 Selectivity 

Crab pots have been developed that will select 

specifically for rock crabs, as discussed in SectIOn 5.11 

(Stasko see footnote 6; Stasko and Graham ee footnote 

13). Various baits, gear types or pot entrance rna) be 

used to select size; spider crabs, Libima emarginata, and 

lobsters, Homarus americanus, are frequently caught In 

crab pots. 

5.43 Catches 

The rock crab fi hery began between 1 

a1. 1973) and 1900 (Turner 1953; \\ ilder 1 
\eloped lowly. Up to 1962. the totallJ.S. cat ch was only 

1 million kg, 'hith a value of 91,000 ('rYilder 1966). Since 

19 2. the indu try has developed more quickly. Annual 

catche increa ed but never exceeded 230,000 kg in 

anada ( addy et al. 1974). Commercial landings in 

• Te'h Jersey began in 1959; since then catches have increa ed teadily up to 157.000 kg m 1974 (McHugh and 

William 1975). Figure 11 and Table 20 summarize 

( ancer • pecle landings in Rhode Island including rock 

and Jonah crab . Per vessel catches in Canada are de-

. cribed by Wilder (1966). In 1963, the daily crab catch 

per boat varied trom 68 to 1.818 kg. One boat m the Pugwa. h, . Tova Scotia, region reportedly averaged 863 kg/ 

day from 5 eptember to 10 October. 

atche per crab pot are di cussed in Shotton (1973) 

and ~tako (see footnote 6). 

6 PROTE 'TION A~D MANAGEMENT 

6.1 Regulatory (legislative) measures 

6.11 Limitation or reduction of total catch 

At pre ent, there are no limits on total catch of C. irr ratus on an annual basis. However, some states have 

g neral laws concerning "edible crabs." For example, 

(hapter laO, Section 37 (Lobsters and crabs; license, 

regulation.; violations) of the Massachusetts General 

Law pecifies that noncommercial, daily catches shall 

not exceed 50 crabs in 1 day. Permits are required for all 

fi hermen taking edible crabs commercially or non -

commercially in Massachusetts (Chapter 130, Sections 

:3 and J). Commerical fishermen must pay $15 for a 

general shellfi h license and $50-$100 for a boat license, 

dependmg on the total length of the vessel. Noncommerciallicen e. for crabs for use with up to 10 pots or 

diving are 15. 

6.12 Protection of portions of population 

\1 !II r (1976) detailed the regulations of all North 

m ncan commercial crab fishenes. Cancer irroratus 

.... not mcluded in the study smce the extent of its 

pi Itation did not warrant protection. Instead, some 

t t and Canada have legi lated protective measures 

th t ar applIcable to all fisheries or the edible crabs. 

{ mpetltlOn among fi hermen for the .. ew England 

k (r b populatlOn~ led to legislative action at the state 

early a 1 37. t that time Massachusetts passed 

prohibiting the taking of rock crabs between 1 

mb r nd 11 larch (Ma~sachu etts General Laws, 

pt r 1) ctlOn 0). 

II ctlOn of female crab~ I regulated in several 

1 hu t <Gate. et al. 1974) and Rhode 

peci I p rmits trom the respective Detural Re oure . before collecting female . 

th M a hu" tt General Law (Chapter 

ndltl n under which ovigerou' lemale 

car p c .... ,dth ha been e tabli hed in 

22 

MO 

120 

250 I I/) I 

0 I 

Z I 100 I :::> I 

0 I 

Q. 2 I i

~ I 

I 80 C

0 I 

I i I/) I 0 ISO z 

~ I 60 c

I 

:::> I 

0 I 

I X 100 I ~ I 40 I 

I 

I 

SO I 

I 

I 

1935 1945 ~ 1975 

Figure Il.-Rhode Island commercial landings for the Cance

irroratus and C. borealis combined. (From Olsen and Steven

son 1975.) 

Table 20.-Commercial crab (Canc er irroratus and C. boreali

combined ) landings and values in Rhode Island waters betwee 

197 1 and 1973. (From Olsen and Stevenson 1975.) 

Year kg X 1,000 Cc total kg $ X 1,000 "<> total 

1971 0 0 

1972 31.9 0.1 19 0.1 

1973 93.6 0.2 46 0.3 

law; practicality and percent meat yields have effectivel 

placed a lower limit on commercial crab sizes of 89-mm 

carapace width (Scarratt and Lowe 1972). Even unde

the most favorable ratios of meat to wet weight, up to 45 

crabs are required to yield 1 kg (approximately 20 crab

for lib) of meat (Turner 1953). (See Table 19.) 

To gather statistics and maintain proper manage 

ment efforts, the Commonwealth of Massachusetts re 

quires the Director of Marine Fisheries to collect catcH 

data (number of crabs, type of gear used, cost of gear

and number of employees) from each gear or boat owne 

(Chapter 130, Section 33 of Massachusetts Genera 

Laws). 

6.3 Control or alteration of chemical features of the 

environment 

6.3 1 Water pollution control 

Many metals are important in the maintenance 0 

enzymatic and respiratory systems in Cancer irroratus 

These metals often form the active centers for ke 

organic molecules. Martin (1973, 1974) analyzed severa 

adult rock crabs in attempts to study the metal conten 

a re lated to the crabs' needs. To minimize variability 

all crabs were in intermolt stage C. (Passano 1960) 

Table 21 summarizes the whole body concentrations 0 

metals in rock crabs collected from "nonpolluted" waters 

In his more recent studies, Martin (1975, 1976) ha 

analyzed rock crab eggs and ovaries for concentrations 0 
Fe, Cu, Zn, Mg, Mn, and Co. Some of the metals (Fe, 

Mn, and Mg) induced increased metabolism rates during 

embryogensis that were independent of the water content 

of the embryos. Decreases in concentrations of Cu and Zn 

were correlated to increased water content in embryos. 

Possible effects of hydrocarbons have also been 

studied. The water accomodated fraction (WAF) of No.2 

fuel oil has been shown by Bigford (1976, 1977) to significantly alter larval responses to light, pressure, and 

gravity. In general, exposure to 0.1 and 1.0 ppm WAF depressed movements of larvae in the early stages and 

enhanced many of the same movements in late stage larvae. When compared to the control larvae (approximately 0.0 ppm), the oil-exposed larvae were significantly lower in vertical column tests during zoeal stages 

I-m and higher in stages V and megalopae; stage IV was 

similar in all three oil treatments. These differences in 

larval behavior could lead to exposure to various physical 

factors (water currents, temperature, salinity) that could 

alter mortality and recruitment. Losses via volitilization 

during the above study (Bigford 1976, 1977) reduced the 

oil concentrations sufficiently to permit larval development at the 1.0 ppm WAF concentration. However, 

continuous exposure experiments indicated that 1.0 ppm 

WAF is lethal to rock crab larvae within several days 

(Pechenik et a1. in press). 

Adult rock crabs surveyed in Chedabucto Bay, Nova 

Scotia, throughout the year exhibited bunker Coil 

accumulation ranging from 2.5 to 17 times that of controls (Scarratt and Zitko 1972). 

6.4 Control or alteration of the biological features of 

the environment 

6.43 Control of parasites and disease 

Antibiotics have been used to control bacterial infestations in laboratory cultures of rock crab larvae. Sastry 

(1970) added penicillin to his cultures. Bigford (see footnote 5) used streptomycin and penicillin in small, individualized cultures. In the latter case, a comparison between the treated and untreated cultures revealed that 

survival and development times were significantly better 

in the treated water. Suvival to megalops and the first 

Table 21.- Average concentrations of metals (ppm) in whole Cancer 

irroratus adults expressed as ratio of wet weight, dry weight, and 

ash, ± 1 standard deviation. A, average body size in mm; B, 

average % H,Oas ratio of wet weight; C, average % ash as ratio of 

dry weight. (From Martin 1974.) 

Metal Wet weight Dry weight Ash 

Zn 30.5± 10.2 103.0± 29.5 284.8± 87.8 

Cu 19.9± 11.8 66.8± 37.2 IB4.2± 105.2 

Fe 60.0± 28.0 205.6± 105.3 570.7± 294.3 

Mn 10.6± 4.2 35.8± 13.8 98.9± 41.1 

Mg 3100.9± 340.0 10,556.5± 854.8 28,994.3± 1,965.4 

Ca 51,169.0±5,471.4 174,408.6± 13,713.0 478,539.0±15,941.5 

Sr 673.3± 70.4 2,293.5± 150.0 6,297.9± . 234.2 

Na 8,854.9±l,799.5 30,343.8± 6,526.4 83,428.0±18,OI0.2 

K 2,949.3±l,023.5 10,080.4± 3,450.0 27,820.9± 9,813.3 

A B C 

78.97± 15.56 70.65± 3.22 36.43± 2.40 

23 

crab stages were 83.3% and 61.1% with antibiotics and 

16.6% and 2.7% without. 

Ultraviolet sterilizing units have been attached to 

some laboratory culture systems (Sastry 1970) to minimize bacterial infestations. 

7 CULTURE 

No information is available concerning concentrated 

rock crab culture efforts. However, Bigford 14 ha 

summarized the culture methodology used in hatching 

and maintaining larvae in the laboratory. 

ACKNOWLEDGMENTS 

The author is deeply indebted to E. D. Schneider, D. 

K. Phelps, and A. D. Beck of the Narragansett, R.I., 

U.S.A. Environmental Research Laboratory (EPA), for 

providing the encouragement and support necessary to 

complete this manuscript. P. A. Haefner, Jr., W. H. 

Lang, and J. A. Pechenik, plus the anonymous reviewers 

of the NOAA Technical Report NMFS Circular series, 

are thanked for their significant contributions to the 

text. 

Some of the drawings and figures were completed with 

the aid of Annette Doherty, James Brennan, John 

Cardin, and Kenneth Zbyszewski. The manuscript was 

typed by Josephine DeVoll and Dale-Marie Ritchie . 

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_S--GE'O" t9~698-210 13