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.

A method is described for catching the planktonic larval stages of the lobster (Homarus ame,icanus Milne Edwards). Estimates are made of the abundance and distribution of each of the four stages in the surface waters of part of the Northumberland Strait (southern Gulf of St. Lawrence) fir the years lg4g-6l,with a more critical analysis for the year 196I-Both abundance and survival of the larvae lr.ry irorn year to year, although they do not appear to be related with measured hydrographical conditions. It is suggested that the distribution of stage I larvae reflects the iocation of the parent stock and that surface drift carries the developing larvae to possible areas of settlement.There is no conclusive relationship between the larvae and the subsequent stock, although a possible relationship between the abundance of stage I larvae and parent stock density is de' scribed and briefly discussed. lReceived for publication December 30' 1963' 661 J. Frsn. Rrs. Bo. CANAoe, 2l(4)' 1964. Printed in Canada.

Abundance, survival, and vertical and diurnal distribution of lobster larvae in Northumberland Strait, 1962-63, and their relationships w.ith commercial stocks. J. Fish. R.es. Board Can' 30: 181'9-1824. Estimates of the abundance of the four planktonic stages of lobster larvae (Homarus americanus) taken in a large surface plankton net show that production and survival of larvae in Northumberland Strait in 1962 and 1963 were the lowest on record. Examination of diurnal fluctuations in abundance, and sampling below the surface and at various depths to the bottom, confirm that larvae are concentrated at the surface during daylight hours. The time to next molt of stage IV larvae, captured and retained alive, indicates that settlement takes place about midway ihrough stage IV. Reexamination of earlier results together with these _new data now sgggests there is some evidence for a relationship between stage IV larval abundance and subsequent commercial lobster stocks, but that sampling errors are too great to permit accurate prediction. Sctnurr, D. J. 1973. Abundance, survival, and vertical and diurnal distribution of lobster larvae in Northumberland Strait, 1962-63, and their relationships with commercial stocks. J. Fish. Res. Board Can. 30: 1819-1824.

An energy-flow diagram for the bottom community in the seaweed zone of St. Margaret's Bay, Nova Scotia, has been constructed, using previous estimates of seaweed production and observations on animal biomass and respiration rates. Annual seaweed production exceeded the annual consumption by herbivores by a factor of more than 10 (7000 vs. 572 kcal/m2 per year). This fact, plus observations of physical processes in the seaweed zone, indicate that most of the seaweed production is exported as particulate matter in suspension. Production rates of the American lobster (Homarus americanus) prey species exceed lobster ingestion rates, also by a factor of more than 10 (84 vs. 6 kcal/m2 per year). The difference is presumably consumed by lobster competitors. The available information suggests lobster production in the seaweed zone could be increased by reducing predation and competition for food, together with an increase in suitable shelter.

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