Food, Feeding, and Condition of Lobsters, Homarus americanus, Throughout the Seasonal Cycle in Bonavista Bay, Newfoundland

1973 ◽  
Vol 30 (12) ◽  
pp. 1905-1909 ◽  
Author(s):  
G. P. Ennis
Keyword(s):  
Physiological Condition ◽  
Feeding Activity ◽  
Homarus Americanus ◽  
Spider Crab ◽  
Sea Stars ◽  
Molting Cycle ◽  
Cancer Irroratus ◽  
Rock Crab ◽  
Hyas Araneus ◽  
Very High

The rock crab, Cancer irroratus, and spider crab, Hyas araneus, made up about 50% of the food of lobsters in Bonavista Bay, Nfld. The sea urchin, Strongylocentrotus dröbachiensis, several species of molluscs, and several species of sea stars made up 7.1, 10.9, and 10%, respectively. The remainder was mainly a variety of bottom invertebrates but fish and seaweeds were also fairly common. There was a change to a slightly more calcium-rich diet during the molting season. A rapid increase in feeding activity during the summer coincided with increasing temperatures, but despite decreasing temperatures during the fall, feeding activity remained high. The feeding index for females remained high longer into the winter than for males. Physiological condition was directly related to the molting cycle. Premolt condition was very high, postmolt very low, and recovery to the intermolt condition was attained about [Formula: see text] months after the peak molting period.

scholarly journals A field-based investigation of behavioural interactions between invasive green crab (Carcinus maenas), rock crab (Cancer irroratus), and American lobster (Homarus americanus) in southern Newfoundland

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e8444
Author(s):  
Nicola Zargarpour ◽  
Cynthia H. McKenzie ◽  
Brett Favaro
Keyword(s):  
Carcinus Maenas ◽  
Positive Association ◽  
Homarus Americanus ◽  
Green Crab ◽  
American Lobster ◽  
Catch Per Unit Effort ◽  
Cancer Irroratus ◽  
Species Invasions ◽  
Rock Crab ◽  
Catch Rates

Marine species invasions pose a global threat to native biodiversity and commercial fisheries. The European green crab (Carcinus maenas) is one of the most successful marine invaders worldwide and has, in the last decade, invaded the southern and western coastal waters of the island of Newfoundland, Newfoundland and Labrador (NL), Canada. Impacts of green crab on the American lobster (Homarus americanus), which are native to Newfoundland, are not well understood, particularly for interactions around deployed fishing gear. Declines in lobster catch rates in invaded systems (i.e., Placentia Bay, NL), have prompted concerns among lobster fishers that green crab are interfering with lobster catch. Here, we conducted a field experiment in a recently-invaded bay (2013) in which we deployed lobster traps pre-stocked with green crab, native rock crab (Cancer irroratus) (a procedural control), or empty (control). We compared catch per unit effort across each category, and used underwater cameras to directly observe trap performance in situ. In addition, we used SCUBA surveys to determine the correlation between ambient density of lobster and green crab in the ecosystem and the catch processes of lobster in traps. We found: (1) Regardless of the species of crab stocked, crab presence reduced the total number of lobster that attempted to enter the trap, and also reduced entry success rate, (2) lobster consumed green crab, rock crab and other lobster inside traps and (3) there was a positive association between lobster catch and ambient lobster density. Our results suggest that while there was a relationship between in-trap crab density and trap catch rates, it was not linked to the non-native/native status of the crab species.

Trapping interactions of crabs and American lobster in laboratory tanks

1995 ◽  
Vol 52 (2) ◽  
pp. 315-324 ◽  
Author(s):  
R. J. Miller ◽  
J. T. Addison
Keyword(s):  
Interspecific Interactions ◽  
Carcinus Maenas ◽  
Homarus Americanus ◽  
American Lobster ◽  
Target Species ◽  
Cancer Irroratus ◽  
Rock Crab ◽  
Trap Catches ◽  
The Relationship ◽  
Index Of Abundance

The relationship between trap catches of decapods and their abundance is not well established. Because it is difficult to manipulate density in the field, laboratory tanks were used to examine 10 hypotheses about the intra- and interspecific interactions of rock crab (Cancer irroratus), green crab (Carcinus maenas), and American lobster (Homarus americanus). The proportion of rock crabs captured did not differ among high, medium, and low densities, but the proportion captured was reduced at high densities for both green crabs and lobsters. Additional experiments demonstrated that large green and rock crabs in the tanks reduced the catch of small green and rock crabs and that the presence of lobsters reduced the catch of both crab species considerably. However, small rock crabs did not reduce the catch of large rock crabs, and neither green nor rock crabs reduced the catch of each other. Reductions in the catch of a target species caused by interactions in the field can perhaps be lessened by removing the catch from the trap at intervals of less than 24 h. Then the catches would be summed over 24 h for an index of abundance.

Biological and physical variables associated with aggregations of the giant scallop Placopecten magellanicus

1995 ◽  
Vol 52 (4) ◽  
pp. 743-753 ◽  
Author(s):  
Kevin D. E. Stokesbury ◽  
John H. Himmelman
Keyword(s):  
Homarus Americanus ◽  
Pseudopleuronectes Americanus ◽  
Placopecten Magellanicus ◽  
Cancer Irroratus ◽  
Risk Of Predation ◽  
Anarhichas Lupus ◽  
Rock Crab ◽  
Surrounding Areas ◽  
Spat Settlement ◽  
Atlantic Wolffish

To identify factors that may determine where aggregations (beds) of giant scallops (Placopecten magellanicus) develop, we compared physical and biological conditions in two scallop beds in Port Daniel Bay, Baie des Chaleurs, Gulf of St. Lawrence, with conditions in seven adjacent areas. Gravel substratum predominantly characterized scallop beds. Physical hydrographic conditions and the intensity of asteroid predation were similar within scallop beds and in surrounding areas with few scallops. High P. magellanicus spat settlement density was not consistently correlated with existing scallop aggregations, but filamentous organisms, on which scallops preferentially settle, were more abundant in scallop beds, possibly enhancing recruitment. Scallop growth rate varied among areas and was intermediate within scallop beds. Winter flounder (Pseudopleuronectes americanus) and Atlantic wolffish (Anarhichas lupus) preyed on P. magellanicus and may influence scallop distribution. Scallop tethering experiments indicated that risk of predation was low within scallop beds compared with adjacent areas. Scallop mortality was positively correlated with mean density of both rock crab (Cancer irroratus) and American lobster (Homarus americanus). We conclude that gravel substratum, low decapod predation, and presence of filamentous flora and fauna are critical factors determining scallop aggregation location.

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