Search

Length and age distribution, together with evidence indicating the annual formation of an opaque and translucent hyaline zone on the otoliths of Greenland halibut (Reinhardtius hippoglossoides), point to the validity of using otoliths in age determination. The high incidence of opaque zones during July–October suggests that these fish grew fastest during this period. Young fish appeared to have a longer annual growth period than the older specimens.

Commercial exploitation of American plaice on the Grand Bank increased from the early 1950s reaching a peak of about 90,000 tons in the mid-1960s. Catches have subsequently declined to about 45,000–50,000 tons annually. The increased exploitation of plaice was reflected in declines in catch per hour and stock abundance of fully vulnerable age-groups and an increase in the rate of instantaneous fishing mortality (F). The documentation of these was particularly strong in ICNAF Division 3L, but appeared to be somewhat erratic in 3N, probably because of incomplete sampling of the stock prior to the mid-1960s.Average size at age increased gradually from the early 1950s to the 1970s apparently because of increased growth rate in the initial 2 or 3 yr of life. Coupled with the increased size at age were significant declines in the age at sexual maturity.Significant correlations were found between stock abundance and asymptotic length (L∞), and size at age 5 and 10 in Division 3L and while positive trends could be demonstrated between some of these and mean bottom temperature, the correlations were not significant.

The peak spawning period of American plaice was the first part of April for Flemish Cap and ranged from the end of April for the Grand Bank and surrounding areas to the first part of June for Labrador–Northeast Newfoundland Shelf. Average bottom temperatures during spawning ranged from about 3.5 C for Flemish Cap and the deep spawning areas to the north, to about −1.3 C for St. Mary's Bay and the northern half of the Grand Bank. For the Southeast Grand Bank, Southwest Grand Bank, and St. Pierre Bank average spawning temperatures were 1.1, 2.8, and 2.7 C, respectively.There was evidence that some older, larger fish spawned first and also that plaice in deep water spawned later than those from shallower depths. At the latter depths light was a possible factor.According to samples from St. Mary's Bay the development of the sex products for spring spawning was apparently controlled by water temperatures during the previous fall and late summer.Fifty per cent of the females from Flemish Cap were mature at 7.8 years, the bottom temperature being almost constant at 3.5 C. For other areas the number of years ranged from 12.2 for the Southwest Grand Bank, with prevalent temperatures 0–3, to 15.2 C for St. Mary's Bay where temperatures were −1 to 1.0 C. For males the range was from 5.3 years for the Southeast Grand Bank to 7.5 years for St. Pierre Bank, no data being available for Flemish Cap.

Invertebrates, principally benthic forms, occurred most frequently in plaice stomachs from the Grand Bank. Fish, almost entirely capelin and sand lance, however, contributed the greatest proportion of total weight: 85% on the southeast part of the bank (ICNAF Division 3N) and 55% in the northeast section (ICNAF Division 3L).A seasonal feeding cycle was difficult to document because of the lack of winter samples, however, a greater proportion of empty stomachs occurred in February and March. The greater average weight of contents in spring samples (April–June) in Division 3L and in fall samples (October–November) for Division 3N was probably related to the availability of capelin and lance. The greater annual consumption of capelin and lance in Division 3N apparently accounted for the estimated higher caloric values of the average contents in this division than in Division 3L.

Growth curves of American plaice (Hippoglossoides platessoides Fabricius) from the Grand and St. Pierre banks and the areas east of Newfoundland are presented. Ages were determined using otoliths from random samples collected by research vessels in the spring and summer during 1957–63.For the localities sampled, American plaice on the southern half of the Grand Bank are the largest and the St. Mary's Bay population the smallest at comparable ages. A positive association was found between the sizes at ages 5 and 15 for the various localities and the probable bottom temperatures.Samples of otoliths from St. Mary's Bay indicated that the greatest growth occurs during the May–November period.Year-class dominance was noted for St. Mary's Bay, but not for other areas.

Fecundity estimates were made on a total of 140 mature American plaice from the southern and northern slopes of the Grand Bank and from St. Mary's Bay. Log–log relationships were established between fecundity and fish length, gutted and gilled weight, age, and ovary weight. No differences were found to exist between the fecundity–length relationship of plaice from the three areas, but there is a suggestion that within areas there may be annual differences in egg production. At comparable ages plaice from the southern slope of the Grand Bank are larger in size and produce more eggs than those from the northern slope and St. Mary's Bay.

Vertebral numbers of American plaice in the Northwest Atlantic are compared. Counts ranged from 42 to 48 vertebrae excluding the urostylar half-vertebra.No significant difference was found between vertebral averages of males and females.Averages for an area extending from the Northeast Newfoundland Shelf southward over the whole of the Grand Bank and inshore to include St. Mary's Bay are statistically similar. The average for this area is significantly higher than averages for the Gulf of St. Lawrence, the Labrador Shelf, Flemish Cap and Fortune Bay. However, over the whole area differences are not very great, the range of averages being (for a sample of 30 or more) 45.273–45.806 vertebrae.The possible effects of differences in the time of spawning, larval drift and the inclusion of a large number of year-classes in the various samples are discussed as possible explanations for the low degree of variability in the whole area.The vertebral averages of the year-classes 1942–1953 from St. Mary's Bay are not statistically different.

It was definitely established in July, 1950, that capelin were spawning on the Grand Bank. Samples of spawn taken in 1950 on the Southeast Shoal of the Grand Bank indicate that capelin were spawning in temperatures as low as 2.8 °C. In 1951 spawning temperatures were some two degrees higher. These temperatures are 2 to 4 °C. lower than those reported for beach spawning. Capelin, apparently, also spawn on other areas of the bank. The effects of low temperature in 1950 resulted in spawning taking place in the middle of July and the subsequent slow incubation of the eggs would result in larvae being liberated late in September. In 1951 capelin spawning, in the same area of the Grand Bank, took place around the latter part of June or the first of July and larval liberation around the first of August.Meristic studies using vertebral counts indicate that except for the 1950 year-class there is no real difference between any group from Grand Bank areas. The over-all averages for all years from the Grand Bank do not differ significantly from those found inshore by Templeman (1948).Up to the time of spawning the male capelin were found to be the more numerous.

Tag returns suggest that the Grand Bank supports a number of relatively sedentary populations of plaice. Apparently no significant migrations between coastal and offshore areas occur.A total of 4653 American plaice were marked using Petersen disc tags at six localities on the Grand Bank and one in St. Mary's Bay. Total returns ranged from 1.4% for St. Mary's Bay to 41.6% for the east slope of the Grand Bank. Most were recovered less than 30 miles from the tagging site even up to 7 years after tagging.There was some indication that plaice change their depth location seasonally.

From the study of samples of capelin in their first year it was established that scales are acquired when the fish are a little less than one year old and range in size from 7.2 to 10.0 cm. total (extreme tip) length. Length frequency and age data indicate that there is great variation between the growth rates of the various year-classes.From the Grand Bank 96% of the mature males and 99.6% of the mature females were three years old. No five-year-old fish were found on the Grand Bank. The average total lengths of mature capelin from bank and shore areas are quite similar.The male capelin has a total length greater than that of the female. This difference increases from 0.22 cm. for one-year-old fish to 2.32 cm. for three-year-old spawning fish.

not available

The commercial yellowtail flounder (Limanda ferruginea) fishery on the Grand Bank is comprised of fish age 4–12 with the main contribution from 6–8-yr-olds. Comparison of Grand Bank yellowtail with those reported for the Scotian Shelf indicates similar growth curves. The New England stocks are significantly larger at comparable age probably because of higher water temperatures.

The selected or preferred temperatures of the carp were determined for six acclimation temperatures. At 10 °C., 15 °C., 20 °C., 25 °C., 30 °C., and 35 °C. acclimation the selected temperatures were 17 °C., 25 °C., 27 °C., 31 °C., 31 °C., and 32 °C. respectively. The final preferendum of carp was found to be 32 °C.

Three eelpouts, Lycodes lavalaei, with gills infested by the parasitic copepod Tanypleurus alcicornis (Caligoida: Tanypluridae) were collected on the Grand Banks off Newfoundland. As many as 42 parasites were recorded from one fish. The copepods caused extensive damage to the gill filaments. Anemia and emaciation were apparent in the infested fish.

not available

A single specimen of the hatchetfish Sternoptyx diaphana Hermann was caught at the surface on the southeast part of the Grand Bank. The most northerly records for the North Atlantic are from locations east of the Grand Bank in the Gulf Stream.

Fecundity estimates made on 51 mature yellowtail flounder (Limanda ferruginea) from the Grand Bank ranged from 350,000 to 4,570,000 eggs per female. Fecundity depended mainly on body length and to a lesser extent on age.