81 
Abstract— Biweekly ichthyoplankton 
surveys were conducted in Penobscot 
Bay, Maine, during the spring and early 
summer of 1997 and 1998. Larvae from 
demersal eggs dominated the catch 
from late winter through spring, but 
not in early summer collections. Larval 
fish assemblages varied with tempera- 
ture, and to a lesser extent, plankton 
volume, and salinity, among months. 
Temporal patterns of larval fish abun- 
dance corresponded with seasonality 
of reproduction. Larvae of taxa that 
spawn from late winter through early 
spring, such as sculpins ( Myoxocepha - 
lus spp.), sand lance (Ammodytes sp.), 
and rock gunnel ( Pholis gunnellus ) 
were dominant in Penobscot Bay in 
March and April. Larvae of spring 
to early summer spawners such as 
winter flounder ( Pleuronectes america- 
nus) Atlantic seasnail ( Liparis atlan- 
ticus), and radiated shanny ( Ulvaria 
subbifurcata ) were more abundant in 
May and June. Penobscot Bay appears 
to be a nursery for many fishes; there- 
fore any degradation of water quality 
during the vernal period would have 
wide reaching effects on the nearshore 
fish community. 
Manuscript accepted 6 July 2000. 
Fish. Bull. 99:81-93 (2001). 
Dynamics of larval fish abundance 
in Penobscot Bay, Maine 
Mark A. Lazzari 
Maine Department of Marine Resources 
RO. Box 8 
West Boothbay Harbor, Maine 04575 
E-mail address: mark.lazzari@state.me.us 
For most fish, the greatest mortality 
occurs during early life stages (Hjort, 
1914; Cushing, 1975; Leggett and Deb- 
lois, 1994 >. Therefore, it is essential that 
fish eggs and larvae develop in favorable 
habitats that maximize the probability 
of survival. Bigelow (1926) recognized 
the significance of the coastal shelf for 
the production of fish larvae within the 
Gulf of Maine, noting that most larvae 
were found within the 200-m contour. 
He also observed that larval drift was 
generally to the southwest and that 
abundance increased progressively to 
the west with the result that few larvae 
were observed off eastern Maine and 
in the Bay of Fundy. Other surveys 
(Fish and Johnson, 1937; Marak, 1960; 
Marak and Colton, 1961; 1962) further 
defined the composition of the ichthy- 
oplankton of the Gulf of Maine. Ich- 
thyoplankton of inshore waters of the 
Gulf of Maine has been documented 
for the Damariscotta, Sheepscot, and 
Sullivan Harbor estuarine systems and 
nearby waters in the central area of 
the Maine coast (Graham and Boyar, 
1965; Graham, 1972; Chenoweth, 1973; 
Hauser, 1973; Lee, 1975; Laroche, 1980; 
1982; Shaw, 1981; Townsend, 1981; 
1983; 1984). However, the ichthyoplank- 
ton of Penobscot Bay has not been 
studied despite the fact that it is the 
largest embayment in the region and 
that coastal environments, such as bays 
and estuaries, may constitute favorable 
habitats for the early life stages of a 
large number of marine fishes (Frank 
and Leggett, 1983). 
This study describes the results of a 
two-year, spring survey of larval fishes 
in Penobscot Bay, Maine. The objectives 
of the study were 1) to describe the 
structure of the larval fish community, 
2) to determine the temporal and spa- 
tial variation in species diversity and 
abundance, and 3) to relate these vari- 
ations to differences in location and en- 
vironmental variables. 
Materials and methods 
Field methods 
Penobscot Bay is a large (80-km) 
drowned river valley typical of the 
Maine coast. It has a drainage area 
of over 21,000 km 2 (Haefner, 1967). 
The study area is about 40 km long 
and varies in depth from 15 to 110 m. 
Sixteen ichthyoplankton stations (Fig. 
1) were selected to encompass Penob- 
scot Bay for the larval surveys. Six 
upper bay stations ( R1-R6) were located 
in the northern estuarine portion of 
the bay between Isleboro Island and 
the mainland. Seven midbay stations 
(B1-B7) were located in the central 
portion of the bay. Three lower bay 
stations (02-04) were located in the 
sourthern estuarine portion of the bay 
adjacent to the islands of North Haven 
and Vinalhaven. 
In 1997, seven, two- or three-day 
cruises (97I-97VII) were conducted bi- 
weekly from 4 April through 25 June 
1997 to coincide with spring and sum- 
mer spawning times for many fishes. 
Data collection involved towing a 1.0-m, 
333-micron mesh plankton net equipped 
with a General Oceanics flowmeter dur- 
ing daylight hours (Fig. 1). The net 
was hauled for 20 minutes in stepped 
oblique fashion at the surface, at 10 m, 
and at 20 m, or to within 5 m of the 
bottom. At each station, a vertical pro- 
file of salinity and temperature was col- 
lected with a Seabird 19 CTD (conduc- 
tivity, temperature, and depth) probe. 
