387 



AbStraCt.-Age and growth of 1,746 

 Atlantic herring, Clupea harengus, lar- 

 vae collected in the Nantucket Shoals- 

 Georges Bank region during the au- 

 tumn-winter seasons of 1976-77, 

 1988-89, 1989-90, 1990-91, 1991-92, 

 1992-93, and 1993-94 were deter- 

 mined by enumerating the daily growth 

 increments of their sagittal otoliths. 

 Growth with respect to length for each 

 of the years was best described by a 

 Gompertz curve. Owing to severe 

 weather events in November, January, 

 and February of the 1976-77 season 

 which disrupted the fishes' feeding regi- 

 men, growth was much slower (0.16 

 mm/d) than in more recent years. 

 Lower daily food consumption was re- 

 flected in the rapid and continual de- 

 crease in otolith diameter during the 

 autumn and winter of 1976. Growth for 

 the other six years was strong, showed 

 only minor interseasonal fluctuations 

 (0.22-0.24 mm/d), and ranged intra- 

 seasonally from a high of just over 0.40 

 mm/d in October to a low of 0.04 mm/d 

 in February. 



A general model of larval herring 

 growth was constructed with data from 

 six recent field seasons. Inverse regres- 

 sive methods were employed to generate 

 a composite growth curve with confidence 

 limits for predicting age (days) for a given 

 standard length (mm) from hatching 

 until the onset of metamorphosis. 



Analysis of otolith growth revealed a 

 dramatic increase in the growth rate 

 of the lapillus at about 2.5 months (29.0 

 mm). It is suggested that this increase 

 may coincide with, or immediately fol- 

 low, the filling of the otic bullae with 

 gas and may provide an easily obtain- 

 able marker for estimating the timing 

 of this critical event. The importance 

 of this phase in the life of larval her- 

 ring is discussed, particularly with ref- 

 erence to the 1976-77 season. 



Age and growth of larval 

 Atlantic herring, Clupea harengus: 

 a comparative study 



George R. Bolz 



Woods Hole Laboratory, Northeast Fisheries Science Center 

 National Marine Fisheries Service, NOAA 

 Woods Hole, Massachusetts 02543 



Bruce R. Burns 



Narragansett Laboratory, Northeast Fisheries Science Center 

 National Marine Fisheries Service. NOAA 

 Narragansett, Rhode Island 02882 



Manuscript accepted 5 February 1996. 

 Fishery Bulletin 94:387-397 ( 1996). 



Based on the general assumption 

 that fluctuations in the year-class 

 strength offish stocks are often de- 

 termined by the rate of mortality 

 during the first year of life (Hjort, 

 1914; May 1974; Sissenwine, 1984), 

 ichthyoplankton surveys have been 

 conducted in the Nantucket Shoals- 

 Georges Bank region for more than 

 twenty years. From 1971 to 1979, 

 research cruises designed to gain a 

 better understanding of the early 

 life history of Atlantic herring, 

 Clupea harengus, and its relation- 

 ship to recruitment and spawning 

 stock size were undertaken monthly 

 throughout the autumn and winter. 

 These surveys were coordinated by 

 the International Commission for 

 the Northwest Atlantic Fisheries 

 ( ICNAF ). The United States partici- 

 pation in the program was con- 

 ducted concurrently as part of the 

 MARMAP (Marine Resource Moni- 

 toring, Assessment, and Prediction) 

 program of the Northeast Fisheries 

 Science Center (Sherman, 1980). 

 The MARMAP program was de- 

 signed to measure long-term changes 

 in the variability of larval fish abun- 

 dance off the Northeast coast of the 

 United States and is ongoing. 



In the 1970's, intense fishing 

 pressure by distant-water fleets led 

 to a steady decrease in herring 

 abundance on Georges Bank (An- 



thony and Waring, 1980). Estimates 

 of initial larval abundance declined 

 by 95% from 1975 to 1976 ( Lough 

 et al., 1985). Herring populations in 

 the region began to increase once 

 again in the late 1980s, and this 

 trend has continued into the 1990s 

 ( Smith and Morse, 1993 ). An exami- 

 nation of the age and growth of her- 

 ring larvae, based on the enumera- 

 tion of daily otolith increments, was 

 initiated in 1976 (Lough et al., 

 1982). To understand better the re- 

 covery of Atlantic herring in the 

 Georges Bank area, microstructural 

 analysis of larval otoliths was incor- 

 porated as a routine procedure for 

 each season beginning in the au- 

 tumn of 1988. To date, otoliths from 

 more than 1,700 larvae have been 

 aged. 



The primary goal of this study 

 was to construct an age-at-length 

 curve and a key for field-caught At- 

 lantic herring larvae that describe 

 their growth from hatch until on- 

 set of metamorphosis. Additionally, 

 we compared larval growth during 

 the autumn and winter of 1976-77 

 with that during six recent seasons 

 of 1988-89, 1989-90, 1990-91, 

 1991-92, 1992-93, and 1993-94. 

 Otolith growth was analyzed to de- 

 termine whether changes in the 

 fishes' daily food rations, attribut- 

 able to severe weather, could be de- 



