Some Estimates of Population Density and Feeding Habits of the Rock Crab, Cancer irroratus, in a Kelp Bed in Nova Scotia

1982 ◽  
Vol 39 (4) ◽  
pp. 636-639 ◽  
Author(s):  
N. C. Drummond-Davis ◽  
K. H. Mann ◽  
R. A. Pottle
Keyword(s):  
Nova Scotia ◽  
Population Density ◽  
Sea Urchins ◽  
Feeding Habits ◽  
Atlantic Coast ◽  
Carapace Width ◽  
Hermit Crabs ◽  
Cancer Irroratus ◽  
Kelp Bed ◽  
Rock Crab

The population density of rock crabs (Cancer irroratus) in a kelp bed on the Atlantic coast of Nova Scotia was examined by mark–recapture techniques and found to be about one crab (> 45-mm carapace width) per 2 square metres. Prey taken by the crabs included hermit crabs (Pagurus), mussels (Mytilus), sea urchins (Strongylocentrotus), and various small crustaceans and polychaetes. It was concluded that the crab population would exert a strong predation pressure on these invertebrates.Key words: Cancer irroratus, rock crabs, predation, population density, kelp

Relationship Between Destructive Grazing by the Sea Urchin, Strongylocentrotus droebachiensis, and the Abundance of American Lobster, Homarus americanus, on the Atlantic Coast of Nova Scotia

1981 ◽  
Vol 38 (11) ◽  
pp. 1339-1349 ◽  
Author(s):  
W. G. Wharton ◽  
K. H. Mann
Keyword(s):  
Population Structure ◽  
Nova Scotia ◽  
Sea Urchins ◽  
Atlantic Coast ◽  
Homarus Americanus ◽  
Strongylocentrotus Droebachiensis ◽  
American Lobster ◽  
History Of ◽  
Kelp Bed ◽  
The Relationship

Relationships between percentage cover of macroalgae, population structure of sea urchins (Strongylocentrotus droebachiensis), and the history of the lobster fishery were examined at nine sites distributed along the Atlantic coast of Nova Scotia from Guysborough County in the northeast to Pubnico in the southwest. At Pubnico there was dense algal cover and a small number of urchins living in crevices, and at Cape Sable there was an area of transition, but at all other sites there were urchin-dominated barren grounds. When the population structure of the urchins was compared with that previously observed in St. Margaret's Bay before, during, and after destruction of beds of kelp (Laminaria spp. and Agarum) by overgrazing, it was concluded that kelp bed destruction occurred on the coast north of Halifax prior to 1970, and on the coast south of Halifax after 1970. From the records of American lobster (Homarus americanus) catches it was concluded that a critical decline in catches at each site occurred a few years after kelp bed destruction. Information from various sources is synthesized into a coherent theory of the relationship between lobsters, other predators, sea urchins, and kelp.Key words: lobsters, Homarus americanus; sea urchins, Strongylocentrotus droebachiensis; destructive grazing, kelp, Laminaria, Agarum

Biology of Rock Crab (Cancer irroratus) in Northumberland Strait

1972 ◽  
Vol 29 (2) ◽  
pp. 161-166 ◽  
Author(s):  
D. J. Scarratt ◽  
Robert Lowe
Keyword(s):  
Sex Ratio ◽  
Surface Waters ◽  
Sea Urchins ◽  
Carapace Width ◽  
Late Summer ◽  
Fishing Gear ◽  
Size At Maturity ◽  
Cancer Irroratus ◽  
Rock Crab ◽  
Commercial Size

Divers hand-collected 342 rock crabs (Cancer irroratus) ranging from 4.2 mm carapace width to 97 mm (females) and 127 mm (males). The sex ratio (1.37:1) was biased in favour of males. Of 2929 crabs taken in commercial lobster fishing gear, 92% were above the minimum commercial size of 89 mm, and of these 99.1% were male. Smallest size at maturity was 60 mm for females and 69 mm for males. Breeding occurred in late summer and fall. Larvae were present in surface waters from June to September. Prey of crabs > 25 mm consisted principally of polychaetes, mussels, starfish, and sea urchins. Crabs less than about 65 mm inhabit rocky areas; larger crabs move out onto sand and mud. The fishable population is probably not in significant competition with lobsters for food or space.

Population density and growth of the newly introduced Atlantic rock crab Cancer irroratus Say, 1817 (Decapoda, Brachyura) in Iceland: a four-year mark-recapture study

2017 ◽  
Vol 13 (2) ◽  
pp. 198-209 ◽  
Author(s):  
Óskar Sindri Gíslason ◽  
Jónas P. Jónasson ◽  
Snæbjörn Pálsson ◽  
Jörundur Svavarsson ◽  
Halldór P. Halldórsson
Keyword(s):  
Population Density ◽  
Mark Recapture ◽  
Cancer Irroratus ◽  
Rock Crab

Invasive green crab, Carcinus maenas, on the Atlantic coast and in the Bras d'Or Lakes of Nova Scotia, Canada: larval supply and recruitment

2005 ◽  
Vol 85 (4) ◽  
pp. 847-855 ◽  
Author(s):  
Beth Cameron ◽  
Anna Metaxas
Keyword(s):  
Nova Scotia ◽  
Atlantic Coast ◽  
Carapace Width ◽  
Carcinus Maenas ◽  
Green Crab ◽  
Larval Supply ◽  
Surface Salinity ◽  
Life History Stages ◽  
European Green Crab ◽  
Tidal Signal

Patterns in larval supply and recruitment of the invasive European green crab, Carcinus maenas, were examined at two sites in Nova Scotia, Canada: a typical Atlantic coastal site with high salinity (∼33) and strong tidal signal (Terence Bay); and a microtidal site in the Bras d'Or Lakes, where surface salinity fluctuated from 0 to 23 (Benacadie Pond). Abundance of all life history stages (zoeae, megalopae, juveniles and ovigerous females) was sampled approximately biweekly at each site from June 2001 to June 2002. The reproductive season, based on the presence of ovigerous females, is ∼5 months (June to October) at both sites. Zoeae-I were collected from June to July 2001 and in June 2002 at Terence Bay, and from June to August 2001 at Benacadie Pond. We did not collect later zoeal stages at either site. Megalopae were collected from September to October 2001 at Terence Bay, and from August to September 2001 at Benacadie Pond. Juveniles 1–6 mm carapace width (CW) were present throughout the summer at Terence Bay, and only in autumn at Benacadie. Juveniles 6–12 and 12–27 mm CW were present throughout the summer and autumn at both sites. At Terence Bay, densities of 1–6 and 12–27 mm CW juveniles did not vary among intertidal zones. In contrast, the 6–12 mm CW size-class appeared to move higher in the intertidal through the season, possibly due to effects of predation.

Nectonema (Nematomorpha: Nectonematoidea) a parasite of decapod Crustacea in the Bay of Fundy

1981 ◽  
Vol 59 (6) ◽  
pp. 1193-1196 ◽  
Author(s):  
H. A. Leslie ◽  
A. Campbell ◽  
G. R. Daborn
Keyword(s):  
Hermit Crab ◽  
Hermit Crabs ◽  
Bay Of Fundy ◽  
Internal Organs ◽  
Cancer Irroratus ◽  
Parasitic Castration ◽  
Decapod Crustacea ◽  
Rock Crab ◽  
Juvenile Stages

Juvenile stages of the marine nematomorph genus Nectonema were found in the rock crab, Cancer irroratus, jonah crab, C. borealis, hermit crab, Pagurus acadianus, and the shrimps, Pandalus montagui and P. borealis, in the Bay of Fundy. No effects on the internal organs of most parasitized hosts could be detected although some male rock crabs had atrophied gonads suggesting parasitic castration by Nectonema. In the area of highest parasite incidence 48% of the rock crabs and 11.6% of the hermit crabs sampled were parasitized with Nectonema. Taxonomic work with the genus Nectonema is needed.

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

1972 ◽  
Vol 29 (10) ◽  
pp. 1479-1482 ◽  
Author(s):  
Jay S. Krouse
Keyword(s):  
Life History ◽  
Sexual Maturity ◽  
Size Range ◽  
Gulf Of Maine ◽  
Carapace Width ◽  
Early Spring ◽  
Late Winter ◽  
Early Winter ◽  
Cancer Irroratus ◽  
Rock Crab

Rock crabs, Cancer irroratus, were caught in wire lobster traps from 1968 through 1971 at Boothbay Harbor and in 1969 at Casco Bay, Maine. Females dominated the annual catches (except in Casco Bay) and width classes from 61 to 90 mm; while males were predominant above this size range. Rock crabs from Casco Bay were heavier at a given width than those from Boothbay Harbor. Soft-shelled females were caught mostly in the fall, while soft-shelled males appeared most frequently in late winter and early spring. The occurrence of newly berried females suggested that spawning (egg extrusion) took place in late fall and early winter, and hatching occurred in spring. Most female crabs attained sexual maturity between 70–80 mm carapace width, but a few matured at widths less than 70 mm.

Predation by Rock Crabs (Cancer irroratus) on Diseased Sea Urchins (Strongylocentrotus droebachiensis) in Nova Scotia

1984 ◽  
Vol 41 (12) ◽  
pp. 1847-1851 ◽  
Author(s):  
Robert E. Scheibling
Keyword(s):  
Nova Scotia ◽  
Sea Urchins ◽  
Mass Mortality ◽  
Strongylocentrotus Droebachiensis ◽  
Significant Preference ◽  
Laboratory Findings ◽  
Cancer Irroratus ◽  
Feeding Experiments ◽  
Defensive Behaviors ◽  
Strong Attachment

Predation of morbid sea urchins (Strongylocentrotus droebachiensis) by rock crabs (Cancer irroratus) and other predators was observed using SCUBA during an outbreak of disease in southwestern Nova Scotia in August 1983. Disease increases susceptibility of sea urchins to predation by precluding natural defensive behaviors including spine projection, strong attachment to the substratum, and aggregation. In laboratory feeding experiments, rock crabs preferred diseased or narcotized sea urchins over healthy ones and fed upon them at a much higher rate than crabs given only healthy sea urchins as prey. Rock crabs showed no significant preference between diseased and narcotized sea urchins. Rock crabs clearly preferred mussels over healthy or diseased sea urchins. Although rock crabs do not appear to be important predators of healthy sea urchins, from field and laboratory findings I conclude that they contribute to mass mortality of sea urchins by preying upon morbid individuals during outbreaks of disease.

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