240 
National Marine 
Fisheries Service Fishery Bulletin 
NOAA established in 1881 
Spencer F. Baird 
First U S. Commissioner 
of Fisheries and founder 
of Fishery Bulletin 
Extrusion of fish larvae from SEAMAP plankton 
sampling nets; a comparison between 0,333-mm 
and 0.202-mm mesh nets 
Email address for contact author: christina.schobernd@noaa.gov 
Abstract— To assess larval fish and 
egg extrusion through the standard- 
size mesh plankton net used during 
resource surveys of the Southeast 
Area Monitoring and Assessment 
Program (SEAMAP), 81 bongo tows 
with side-by-side nets, each con¬ 
structed with a different mesh size 
(0.333 mm and 0.202 mm), were 
taken during 5 SEAMAP surveys 
conducted in the Gulf of Mexico dur¬ 
ing 2005-2007. Retention by length 
class for the larvae of 6 taxa and an 
unidentified group was evaluated 
by using 2 deterministic functions 
to estimate the number of larvae 
missed when sampling with the net 
with standard-size mesh (0.333 mm) 
compared with sampling with the 
smaller mesh net (0.202 mm). Small¬ 
er larvae, particularly those between 
1.5 and 3 mm in body length, were 
retained in greater numbers in the 
0.202-mm-mesh net than in the 
0.333-mm-mesh net. Extrusion was 
most pronounced for small, undevel¬ 
oped larvae that could be identified 
only to the suborder Percoidei or 
that could not be identified. Extru¬ 
sion was evident also among larvae 
of taxa in the families Engraulidae, 
Sciaenidae, and Scombridae, but less 
so for Clupeidae and Lutjanidae; the 
latter result was most likely attrib¬ 
utable to a mismatch between the 
timing of sampling and spawning 
seasons. The functional relationships 
presented here, based on larval 
abundance ratios and body lengths, 
represent the first empirically de¬ 
rived estimates of extrusion and size 
bias in SEAMAP ichthyoplankton 
samples. 
Manuscript submitted 30 November 2017. 
Manuscript accepted 8 May 2018. 
Fish. Bull. 116:240-253 (2018) 
Online publication date: 31 May 2018. 
doi: 10.7755/FB.116.3-4.3 
The views and opinions expressed or 
implied in this article are those of the 
author (or authors) and do not necessarily 
reflect the position of the National 
Marine Fisheries Service, NOAA. 
Christina M. Schobernd (contact author ) 1 
M. Conor McManus 2 
Joanne Lyczkowski-Shultz 3 
Nathan M. Bacheler 1 
Denice M. Drass 3 
1 Southeast Fisheries Science Center 
National Marine Fisheries Service, NOAA 
101 Pivers Island Road 
Beaufort, North Carolina 28516 
2 Graduate School of Oceanography 
University of Rhode Island 
21 5 South Ferry Road 
Narragansett, Rhode Island 02882 
3 Southeast Fisheries Science Center 
National Marine Fisheries Service, NOAA 
3209 Frederic Street 
Pascagoula, Mississippi 39567 
Planktonic, early-life-stage fish 
(ichthyoplankton) have been moni¬ 
tored for over a century worldwide 
to assess the abundance and distri¬ 
bution of fish stocks (Hjort, 1914; 
McClatchie et ah, 2014). Ichthyo¬ 
plankton surveys have been used to 
estimate changes in spawning stock 
biomass, to identify spawning habi¬ 
tats and seasonality, and to quantify 
survival through the larval stage 
(Richardson et ah, 2010). Arguably, 
the greatest value of these surveys 
is that they provide a method for 
measuring changes in the trends of 
larval assemblages over time. Such 
trends are particularly valuable dur¬ 
ing a changing climate, since altera¬ 
tions in sea temperature, carbonate 
chemistry, and ocean circulation in¬ 
fluence larval growth, mortality, dis¬ 
persal, and assemblage connectivity 
(Llopiz et ah, 2014). 
In the southeastern United States, 
larval fish abundances are monitored 
under the Southeast Area Monitoring 
and Assessment Program (SEAMAP; 
Stuntz et al. 1 ; Lyczkowski-Shultz and 
Hanisko, 2007). As part of SEAMAP 
protocol, plankton samples are col¬ 
lected during annual surveys in the 
Gulf of Mexico by the National Ma¬ 
rine Fisheries Service (NMFS) and 
agencies of 4 states: Alabama, Flori¬ 
da, Louisiana, and Mississippi. Data 
from these surveys are used in stock 
assessments for many managed, com¬ 
mercially significant species, includ¬ 
ing the bluefin tuna (Thunnus thy Fi¬ 
rms', Scott et ah, 1993), king mack¬ 
erel (Scomberomorus cavalla; Gled- 
hill and Lyczkowski-Shultz, 2000), 
red snapper (Lutjanus campechanus ; 
1 Stuntz, W. E., C. E. Bryan, K. Savas- 
tano, R. S. Waller, and R A. Thomp¬ 
son. 1983. SEAMAP environmental 
and biological atlas of the Gulf of Mexi¬ 
co, 1982, 145 p. Gulf States Mar. Fish. 
Comm., Ocean Springs, MS. [Available 
from website.] 
