INTERNATIONAL COMMISSION FOR THE NORTHWEST ATLANTIC FISHERIES RESEARCH BULLETIN NUMBER 10 Issued from the Headquarters of the Commission Dartmouth, N. S., Canada 1973 Contents PENTTILA, JUDITH A., and BRADFORD E. BROWN. Total Mortality Rates Estimated from Survey Cruise Data for Two Groups of Yellowtail Flounder in the Southern New England and Georges Bank Areas (ICNAF Subarea 5) 5 PARSONS, L. S.. and V. M. HODDER. Some Biological Characteristics of the Fortune Bay, Newfoundland, Herring Stock, 1966-7] 15 NEVINSKY NI. M., and V. P. SEREBRYAKOV. American Plaice, flippoglossoides platessoides platessoides Eabr., Spawning in the Northwest Atlantic Area 23 PARSONS, L. S. Meristic Characters of Atlantic Herring, Clupea harengus harengus I Stock, in Newfoundland and Adjacent Waters 37 JONES, B. W., and J. G. POPE. A Groundfish Survey of Faroe Bank 53 PITT, T. K. Assessment of American Plaice Stocks on the Grand Bank, ICNAF Divisions 3L and 3N 63 LUBIENIECKI. B. Note on the Occurrence of Larval An/saki in Adult Herring and Mackerel from Long Island to Chesapeake Bay 79 TEMPLEMAN, WILFRED. Distribution and Abundance of the Greenland Halibut, Reinhardiius hippoglossoides (Walbaum), in the Northwest Atlantic 83 MINET, J. P. Age and Growth of the American Plaice, Hippoglossoides platessoides, off Cape Breton Island in ICNAF Subdivision 4Vn 99 SCOTT, J. S. Otolith Structure and Growth in Northern Sand Lance, A mmodyies dubius, from the Scotian Shelf I 07 BACKI, F., W. STRZYZEWSKI, and G. ZDZ]EBKOWSKI. The Selectivity of Polish Large-Mesh Topside Chafing Gear Made of Thick Netting Yarn 117 Studies on Georges Bank Herring in 1970 Introductory Note 123 PANKRATOV, A. M., and K. SIGA J EV. Studies on Georges Bank Herring Spawning in 1970 ]25 CADDY, J. F., and T. D. LLES. Underwater Observations on herring Spawning Grounds on Georges Bank 131 GRAHAM, JOSEPH J., and STANLEY B. CHENOWETH. Distribution and Abundance of Larval Herring, Clupea harengus harengus Linnaeus, Over Egg Beds on Georges Bank 141 DRAPEAIJ, GEORGES. Sedimentology of herring Spawning Grounds on Georges Bank 151 Notes MAY, A. W., and W. H. LEAR. Gutted Weight Versus Total Length of Atlantic Salmon at West Greenland 163 Instructions to Authors 167 Total Mortality Rates Estimated from Survey Cruise Data for Two Groups of Yellowtail Flounder in the Southern New England and Georges Bank Areas (ICNAF Subarea 5) Judith A. Penttila l and Bradford E. Brown Abstract Total instantaneous mortality rates were estimated by four different procedures for the southern New England and Georges Bank yellowtail flounder fishing grounds (1CNAF Subarea 5). Mortality rates were determined from research vessel survey data from 1963 to 1969 by the following methods: (1) slopes of the catch curves; (2) ratios of the catch per tow in a given season to the catch per tow of the same season for the previous year; (3) Robson-Chapman formula; and (4) Heinckes formula. Each method showed a lower mortality rate for Georges Bank than for southern New England, with an average of the estimates giving Z = 1.00 for Georges Bank and Z = 1.25 for southern New England. Introduction (Fig. 1) were based on depth and geographic sub- divisions. The number of stations per stratum were The increased level of fishing on yellowtail allocated roughly proportional to the area of the flounder, Limanda ferruginea (Storer), in recent years stratum. made it necessary to establish catch quotas in 1CNAF Subarea 5 in 1971. Assessment of the effects of fishing Season was primarily based on analysis of commercial catch and effort data. To improve and corroborate the assessment Winter Summer Autumn of these stocks, total instantaneous mortality rates for the southern New England and Georges Bank yellowtail Year (Jan-Apr) (July-Aug) (0 ct-Der) flounder fishing grounds were estimated from analyses of research vessel survey data by four different 1963 X procedures. These grounds contain two nearly inde- 1964 X pendent groups of yellowtail flounder (1,ux, 1963). The 1965 X X 1966 X X data used for these analyses were collected on 14 1967 X standardized groundfish survey cruises during the years 1968 X 1963-69. 1969 X X X Length frequencies of catch and scales for age Collection of Data determination were collected routinely. Fish from which scales were taken for aging were identified by sex. In During the years 1963 to the present time, routine most cases the entire catch of yellowtail was measured; surveys have been conducted on the R/V Albatross IV in but in those instances where the catch was quite large, a the southern New England and Georges Bank areas two representative subsample was measured and then the or three times a year. The seasonal distribution of the 14 length frequency of the entire catch was estimated. Prior cruises analyzed in this paper are listed below. to 1969, the fish from which scales were taken were usually subsamples stratified by length and by sex, A Number 36 Yankee trawl with a 4-1/2-inch mesh and except where catches were small enough to permit total a 1/2-inch-mesh liner in the codend was used. All hauls sampling. In 1969, the subsamples of fish were stratified were 30 min in duration. (For a detailed account of the by length only. The sex was recorded for all fish for survey methods, see Grosslein, 1969.) The surveys were which the age was determined. Method of aging was set up on a stratified random sampling design. The strata described by Lux and Nichy (1969). National Marine Fisheries Service, Northeast Fisheries Center, Woods Role, Massachusetts 02543, USA. 6 ICNAF RESEARCH BULLETIN NUMBER 10, 1973 Fig. 1. Strata and areas comprising the southern New England and Georges Bank yellowtail flounder fishing grounds. TABLE 1. Estimated mean catch/tow per age-group for males and females combined for yellowtail flounder from southern New England Year and Age-group season 0 1 2 3 4 5 6 7 8 1963 Autumn .05 16.34 14.89 ]4.49 4.25 .45 .00 .08 1964 Winter .00 .44 8.48 8.35 6.64 2.71 1.10 Summer .00 .67 9.66 4.52 5.93 3.22 .39 .17 Autumn .00 18.62 26.51 4.88 6.19 3.00 1.59 1965 Winter .00 .12 24.47 7.04 1.98 1.26 .59 .03 Summer .00 .64 21.27 14.77 1.69 .12 Autumn .26 11.54 ]7.02 6.16 1.80 1.75 .21 1966 Winter .00 .24 6.17 5.71 3.33 .83 1.08 .52 .07 Autumn .88 35.51 10.94 1.74 .98 .19 1967 Autumn .28 20.05 24.17 11.15 1.40 .42 .07 .11 1968 Autumn .00 10.02 11.95 16.70 1.15 .18 1969 Winter .00 4.67 15.54 22.04 12.41 2.31 .13 Summer .00 .21 14.89 40.45 3.82 Autumn .00 12.83 13.03 22.79 5.77 .18 .05 PENTTILA AND BROWN: ESTIMATED MORTALITY RATES FOR YELLOWTAIL. FLOUNDER 7 Determination of Age and Length Composition used were: off Block Island, Nantucket Shoals, South- west Georges Bank, Southeast Georges Bank, and Females grow faster than males after the age of 2 Cultivator Shoals (Fig. 1). These average sex ratios were years (Lux and Nichy, 1969). Because a fixed number of used to determine sex composition length frequencies on males and females were aged, it was necessary to have the five survey cruises from 1967 to 1969. For the 1969 length frequency data prior to 1969 separated by sex cruises, where age samples were stratified only by length before the age frequency could be expanded properly to and not by sex, ratios of the fish in the age sample estimate the age composition of the total catch. Males provided a valid estimate of the proportion of males and and females were separated in length frequency data for females in the entire catch. the nine cruises from 1963 to 1966, but not for the five cruises from 1967 to 1969. The average sex ratios for Age-length frequencies for the entire catch by sex the latter had to be calculated as follows: Summaries were then determined. Stratified means of numbers were made by strata of the number of males and caught per tow for southern New England and Georges females in length groups for the nine cruises from 1963 Bank per one cm length interval, per age group, were to 1966 on which yellowtail length frequencies were estimated separately for males and females. There were recorded by sex. Five length groups were chosen: 1-25 cases where lengths of fish in the age samples did not cm, 26-30 cm, 31-35 cm, 36-40 cm, and greater than 40 include every length class of all fish caught. The age of cm. Sex ratios were then determined for each length those fish in length classes for which age data was not group within each stratum and cruise and year. Sex available was determined by using the estimates of ratios were averaged over years for each season (winter, neighboring classes. The totals for males and females summer, and autumn) for each length group and were then added to give a combined estimate of the stratum. In those cases where fewer than 100 fish were mean catch per tow per age-group for each yellowtail used to determine a ratio, neighboring strata were ground. These estimates were used to determine the combined to give the ratio for a larger area. The areas instantaneous mortality rates for southern New England TABLE 2. Estimated mean catch/tow per age-group for males and females combined for yellowtail flounder from Georges Bank.