242 
Fishery Bulletin 11 6(3-4) 
95" W 94" W 93" W 92" W 91" W 90" W 89" W 88" W 87” W 86" W 86° W 84" W 83° W 82° W 
-33° N 
-32” N 
-31” N 
-30” N 
-29“ N 
-28" N 
-27” N 
-26° N 
-25° N 
-24° N 
-23° N 
Figure 1 
Locations of the 81 tows conducted with bongo nets with different mesh sizes dur¬ 
ing 5 Southeast Area Monitoring and Assessment Program surveys of ichthyoplankton 
conducted in the Gulf of Mexico between October 2005 and August 2007. Month and 
year of sampling are denoted by symbols at each location. The bathymetric contour 
represents the edge of the continental shelf (-200 m). 
Lousiana 
Mississippi 
Alabama 
• 
▲ 
— ▲ —_ 
XV A 
/■« 
Yl a A 
@ 
\ . A 
A A- El 
© © 
Gulf of Mexico 
Georgia 
Florida 
□ a 
• □ 
□ □ 
Monthly sampling effort 
-200 m 
A 
A 
A 
• 
• 
3 
Oct 
Nov 
May 
Sept 
Sept 
2005 
2005 
2006 
2006 
2007 
iiii i—i—i—i—i 
0 75 150 300 Kilometers 
irrespective of time of day during 24-h survey opera¬ 
tions and resulted in the collection of 35 daytime and 
46 nighttime samples with nets of different mesh size. 
Shipboard handling of the concentration and preser¬ 
vation of samples taken from the nets with different 
mesh size followed standard SEAMAP protocols (Lycz- 
kowski-Shultz and Hanisko, 2007). Samples were pre¬ 
served initially in either 5-10% formalin or 95% etha¬ 
nol. Formalin-fixed samples were later transferred to 
95% ethanol after 48 h; samples initially preserved in 
ethanol were transferred to fresh ethanol after 24-36 
h. All tows were made in a double-oblique pattern from 
the surface to a maximum depth of 200 m (or to within 
2 m of the bottom at station depths <200 m) and then 
back to the surface. Tows were made at ~0.8 m/s (-1.5 
kt) and maintained a targeted towing wire angle of ~ 
45° (Smith and Richardson, 1977). Tow speeds ranged 
from 0.64 to 1.47 m/s (1.24-2.85 kt) and an average 
speed of 0.87 m/s (1.69 kt [standard error 0.03]). Tow 
durations ranged from 1.7 to 26.3 min depending on 
station depth and the consequent tow (sampling) depth 
prescribed by SEAMAP protocols. The volume of water 
filtered by each net was measured with a flow meter 
attached within the net mouth. 
Larval fish abundances were standardized to ac¬ 
count for sampling effort by using volume of filtered sea 
water and maximum depth at which the nets sampled 
and were expressed as ‘number of larvae under 10 m 2 
of sea surface’ (Smith and Richardson, 1977; GSMFC 3 ). 
This standardization was accomplished by dividing the 
number of larvae of each taxon caught in a sample by 
the volume of water filtered during the tow, and then 
multiplying the resultant by the maximum depth of the 
tow in meters and the factor 10. Larval abundances 
were also standardized by volume of water filtered 
alone, and are expressed as ‘number of larvae per 1000 
m 3 of filtered sea water’. This was accomplished simply 
by dividing the number of larvae of each taxon caught 
in a sample by the volume of water filtered during the 
tow, and then multiplying the resultant by the factor 
of 1000 (number of larvae per 1000 m 3 ). 
Fish larvae from the 162 samples collected during 
the 81 tows of paired bongo nets were removed and 
identified to the lowest possible taxon (most often to 
family) at the Plankton Sorting and Identification 
Center of the Sea Fisheries Institute in Gdynia and 
Szczecin, Poland. Fish eggs were also removed and 
enumerated but were not measured or identified. Wet 
plankton volumes were measured by displacement 
(‘displacement volume’) to estimate net-caught zoo¬ 
plankton biomass (Smith and Richardson, 1977). Fol¬ 
lowing established SEAMAP identification and mea¬ 
surement protocols, body length (BL) was measured 
as either notochord or standard length depending on 
caudal fin development of the specimen, to the nearest 
0.1 mm. This is the length reported throughout this 
