CRD 01-17
Session
VII: Flounder Biology and Ecology
|
Settlement
dynamics and the distribution of early juvenile winter flounder
in a northwest Atlantic estuarine nursery |
Session
VII: Flounder Biology and Ecology
Abstract No. VII-1
ORAL PRESENTATION |
John P. Manderson, Jeffrey
P. Pessutti, Carol J. Meise, Donna L. Johnson, and Patricia A. Shaheen
NOAA/NMFS/NEFSC, 74 Magruder Rd., Highlands, NJ 07732
Simultaneous
surveys with experimental traps and beam trawls were performed to examine
the effects of supply-side and post-settlement processes on the distribution
of early juvenile winter flounder in the Navesink River/Sandy Hook
Bay estuarine system, New Jersey. We measured patterns of settlement
with the traps that were constructed of 3mm mesh, captured flounder <7
days post-metamorphosis, but prevented the emigration of older fish
and excluded predators. Juvenile distributions resulting from settlement
as well as post-settlement mortality and emigration were measured with
1-m beam trawls. Similar numbers of newly-settled flounder were collected
in traps in the Navesink River and Sandy Hook Bay from April through
June, 2000, but the timing of settlement varied in space. Fish settled
approximately two weeks earlier in the river (April-May) than in the
bay (May-June) as a result of geographic variation in spring warming. Juveniles
were abundant in trawls within the river, where distributions were
correlated with the settlement pattern measured with traps. Within
the bay, however, juveniles were rare in trawls and their distributions
were not correlated with settlement. Juvenile winter flounder are
generally more abundant in the Navesink River than Sandy Hook Bay during
early summer trawl surveys and our results suggest that this pattern
is primarily the result of spatial variation in the strength of post-settlement
processes (mortality and/or emigration) rather than variability in
the total supply of newly settled fish. However, regional variation
in settlement timing could influence the intensity of post-settlement
mortality through the size dependent mortality processes.
| Winter
flounder avoidance of sediment biogeochemicals |
Session
VII: Flounder Biology and Ecology
Abstract No. VII-2
ORAL PRESENTATION |
Andrew F. J. Draxler1 and
Jessica A. Siclare2
1NOAA/NMFS/NEFSC, 74 Magruder Rd., Highlands, NJ 07732
2Saint Joseph's University, 5600 City Ave., Philadelphia,
Pa 19131
The location of juvenile
winter flounder (Pseudopleuronectes americanus) habitat at the
sediment-water interface in estuaries subjects these fish to environments
characterized by intense biogeochemical gradients in both space and
time. Changes in habitat quality variables (dissolved oxygen, sulfide,
nitrite, ammonium, etc.) of behavioral significance to macrobionts
can occur on scales as small as millimeters and hours. Even in high
energy areas of the Hudson-Raritan Estuary with coarse sandy substrates,
oxygen disappears in the upper few millimeters of the sediment, and
water column oxygen concentrations have been observed to decrease from
250 µM to less than 30 µM in a few days. Bejda et al. (1992)
showed that such periodic reductions of oxygen concentrations (to 70 µM)
have major growth rate implications for young-of-the-year (YOY) winter
flounder. To simulate exposure to biogeochemicals at the seabed, wild
caught YOY winter flounder were held in a sand-bottomed, vertical-flow
tank in which half the sediment area was perfused with manipulated
seawater. Temperature was maintained at 20"0.5°C during 26 experiments
while temporally changing biogeochemical gradients and fish locations
were recorded. The fish responded to declining O2 at approximately
100 µM (3.2 mg/L) by moving to more oxygenated water. Increasing
sulfide concentrations produced a more complex response apparently
requiring in excess of 15-20 µM sulfide to elicit avoidance. Exploratory
trials with nitrite (50 µM) and ammonium (100 µM) showed
no clear avoidance reaction though the fish appeared to be in distress.
|
Growth
rates of juvenile winter flounder, Pseudopleuronectes
americanus, as determined from otoliths, under varying
environmental conditions |
Session
VII: Flounder Biology and Ecology
Abstract No. VII-3
ORAL PRESENTATION |
Carol J. Meise, Donna
L. Johnson, Linda L. Stehlik, John P. Manderson, and Patricia A.
Shaheen
NOAA/NMFS/NEFSC, 74 Magruder Rd., Highlands, NJ 07732
Fluctuations
in juvenile winter flounder growth rates have been attributed to large-scale
fluctuations in temperature, and smaller scale factors such as predator/prey
abundances. This study examines individual growth rates of wild field-caught
species as determined through otolith increment counts, and laboratory,
through changes in standard length of juvenile winter flounder throughout
the settlement period (April-July). The duration of the settlement
season for laboratory fish kept at a constant temperature and fed wild
zooplankton, had highly variable growth rates that declined significantly
during the settlement period. General additive models were used to
examine field growth rates and their relationship to environmental
variables. In studies using caged fish, relationships between growth
rate and temperature results were curvilinear; we found a significant
positive linear relationship with growth rate. While growth rate variability
remained high throughout the settlement period, growth rates increased
and growth rate variability decreased as fish size grew, indicating
possible size selectivity for growth.
| Size-related
shifts in habitat associations of young-of-the-year winter flounder
(Pseudopleuronectes americanus): field observations and
laboratory experiments |
Session
VII: Flounder Biology and Ecology
Abstract No. VII-4
ORAL PRESENTATION |
Presentation
Beth A. Phelan1,
John P. Manderson1, Allan W. Stoner2, and Allen
J. Bejda1
1NOAA/NMFS/NEFSC,
74 Magruder Rd., Highlands, NJ 07732
2NOAA/NMFS/Alaska
Fisheries Science Center, 2030 S. Marine Science Dr., Newport, OR 97365
Size-related changes in the
preference young-of-the year winter flounder (Pseudopleuronectes
americanus) (15-69 mm SL) for vegetation and sediment structure
were examined in field surveys and laboratory experiments. In the field,
winter flounder were generally more abundant in vegetated habitats,
but sediment relationships changed with body size. Generalized additive
modeling indicated that capture probabilities for 10-49 mm SL fish
were higher on sediments with a mean grain diameter < 0.5 mm, while
fish 50-95 mm were more frequently collected on sediments of approximately
1.0 mm. In the laboratory, winter flounder (15-69 mm SL) were offered
choices between 1) vegetated substrate [either eelgrass (Zostera
marina) or macroalgae (Ulva lactuca)] and unvegetated azoic
sand, 2) two vegetation types (eelgrass and macroalgae), and 3) a
selection of azoic sediments of different sediment grain sizes. Winter
flounder preferred vegetated substratum (either eelgrass or macroalgae)
to unvegetated substratum but the strength of preference for macroalgal
habitats increased with body size. In the sediment selection experiment,
small individuals (<40 mm SL) preferred fine sediments while larger
individuals (>40 mm SL) preferred coarse-grained substrata. Burial
ability increased with body size and fish generally avoided avoided
sediments (gravel) that prevented burial. Our field and laboratory
experiments suggest that juvenile winter flounder show size-related
changes in habitat selection. Early juveniles appear to prefer fine-
grained sediments, while larger and older individuals are more strongly
associated with vegetated habitats and coarser grained substrata.
Keywords: habitat,
winter flounder, sediment, vegetation, size
| Ecological
biogeography and species diversity of the flatfishes (order Pleuronectiformes) |
Session
VII: Flounder Biology and Ecology
Abstract No. VII-5
ORAL PRESENTATION |
Thomas
A. Munroe
NOAA/NMFS/National Systematics Laboratory, National Museum of
Natural History, Washington, DC 20560-0153
Over
716 species of flatfishes are currently recognized worldwide with species
distributed from northern polar waters to southern boreal seas. From
a global perspective, patterns of flatfish species diversity are strongly
asymmetrical; north temperate and polar flatfish species number about
115 (ca. 17% of total diversity); flatfish diversity in southern temperate
and subantarctic waters is considerably lower (only 4% of total diversity);
freshwater flatfishes (only 2% of total diversity) are relatively rare,
but undescribed species, especially in South America, continue to be
discovered. The greatest diversity of flatfish species (ca. 466 species,
68%+ of total diversity) occurs in shallow (100 m or less), tropical,
marine waters on the inner continental shelf and in nearshore neritic
habitats. Approximately 36% of flatfish species occur in neritic habitats,
272 species (39% of total diversity) inhabit inner continental shelf
habitats, 153 species (22%) live on the outer shelf and upper slope,
and 18 species (3%) occur only on the continental slope. Species diversity
varies widely among the 13 different flatfish families currently recognized:
the Paralichthodidae, Psettodidae, Citharidae, Scophthalmidae and Achiropsettidae
are families of low species diversity; the Samaridae, Rhombosoleidae,
Poecilopsettidae and Achiridae are families with medium species diversity. The
most diverse flatfish families include the Pleuronectidae, Paralichthyidae,
Cynoglossidae, Bothidae and Soleidae.
Keywords:
flatfish, Pleuronectiformes, species diversity, biogeography
