PHYSICAL CHARACTERISTICS OF HERRING EGG BEDS ON THE 



EASTERN MAINE COAST 



David K. Stevenson and Robert L. Knowles 



Maine Department of Marine Resources 



W. Boothbay Harbor, ME 04575 



ABSTRACT 



Herring egg bed surveys were conducted at four sites on the 

 eastern Maine coast in 1985, 1986, and 1987 using a small 

 remotely operated underwater vehicle ( Mini-Rover ) , two types of 

 benthic grab sampler, SCUBA divers, a depth recorder, and a side- 

 scan sonar. Eggs were often visible in a continuous carpet 1-3 

 cm thick on a gravel, sand, and shell fragment substrate. Egg 

 bed perimeters in some cases were fairly abrupt and were defined 

 by changes in substrate. Eggs at one large site in 1986 were 

 distributed over an area 0.8 km 2 in size in depths of 20-35 m. 

 Egg cover at this site was absent or very light in rocky areas 

 and where gravel was absent from surficial sediments. Egg 

 density and abundance were higher in the deeper, offshore 

 portion of this bed, reaching maximum values of 454/cc and 7.2 

 million/m 2 . The total number of eggs spawned at this site was 

 estimated as 2-3 ■ 10 12 , requiring 8,000-15,000 metric tons of 

 spawning fish. Egg mortality and differences in egg development 

 rates at the top and bottom of the egg mat were negligible, 

 indicating that the eastern Maine coast provides optimum 

 conditions for herring egg deposition and survival. Sampling 

 tools tested in 1987 are expected to expand the ROV's research 

 capability by integrating video observations with quantitative 

 samples of eggs, sediment, and larvae. 



INTRODUCTION 



Atlantic herring ( Clupea harenqus L. ) deposit eggs in 

 discrete beds on the bottom in depths ranging from very shallow 

 water to approximately 100 m. Spawning occurs either in the 

 spring or the fall; fall spawners spawn in deeper water than 

 spring spawners. In the Gulf of Maine, herring spawn in the late 

 summer and fall (August-November) in depths of 10-100 m. 

 Principal spawning grounds are located in coastal waters 

 southwest of Nova Scotia, in the vicinity of Jeffreys Ledge, and 

 at various places along the Maine coast (Fig. 1) . Herring 

 spawned in large numbers on Georges Bank until the late 1970s. 

 Herring eggs incubate for about 10 days before releasing small 

 (5-7 mm) yolk-sac larvae into the water column. 



Herring egg beds have been observed and studied in a variety 

 of locations in the North Atlantic, mostly in shallow water 

 environments which are accessible to SCUBA divers. Egg bed 

 surveys have been carried out in deeper water (>3 m) primarily 



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