302 
National Marine 
Fisheries Service 
NOAA 
Abstract— The daily deposition 
of growth increments within both 
sagittae and lapilli was validated 
for known-age laboratory-reared 
(18°C) larval northern pike (Esox In¬ 
dus) (9-33 mm in standard length 
[SL]) sampled 1, 7, 14, 22, and 28 
days after hatching. The mean oto¬ 
lith length at hatching was 58.1 
pm (standard deviation [SD] 4.32) 
for sagittae (no. of larvae sampled 
[zi]=30) and 39.04 pm (SD 4.04) for 
lapilli (n=30). For both sagittae and 
lapilli (the otoliths of which were 
examined without polishing), incre¬ 
ments were formed daily and the 
first increment was deposited at 
time of hatching. The relationship 
of otolith size to fish size was lin¬ 
ear for lapilli and exponential for 
sagittae. The size of the sagittae in¬ 
creased more than that of the lapilli 
at about 9 days after hatching—a 
size increase that corresponded with 
an increase in larval wet weight. 
The age of larval northern pike was 
moderately difficult to determine 
from otoliths; the difficulty varied 
according to the size of the larvae. 
Sagittae are preferable for fish lar¬ 
vae of up to approximately 25 mm 
SL, but for larger individuals, lapilli 
are more suitable. On some of the 
otoliths (79% of sagittae and 18% of 
lapilli), a “stress ring” was deposited 
that corresponded with the time of 
sampling from the aquaria. 
Manuscript submitted 30 March 2018. 
Manuscript accepted 14 August 2018. 
Fish. Bull.: 116:302-309 (2018). 
Online publication date: 5 September 2018. 
doi: 10.7755/FB. 116.3-4.8 
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, 
Fishery Bulletin 
established in 1881 •<?» 
Spencer F. Baird 
First U.S. Commissioner 
of Fisheries and founder 
of Fishery Bulletin 
Daily deposition of growth increments in sagittae 
and lapilli of laboratory-reared larval northern 
pike {Esox lucius) 
Datiusz P. Fey (contact author ) 1 
Adam M. Lefk 2 ' 3 
Martyna Greszkiewicz 1 
Email address for contact author: dfey@mir.gdynia.pl 
1 Department of Fisheries Oceanography and Marine Ecology 
National Marine Fisheries Research Institute 
ul. Kod^taja 1 
81-332 Gdynia, Poland 
2 Department of Logistics and Monitoring 
National Marine Fisheries Research Institute 
ul. Kott^taja 1 
81-332 Gdynia, Poland 
3 Department of Fish Biology and Pisciculture 
University of Warmia and Mazury in Olsztyn 
ul. Oczapowskiego 5 
10-719 Olsztyn, Poland 
Identification of the survival mecha¬ 
nisms at early life stages of fish is 
exceedingly important, but it also 
requires the application of appropri¬ 
ate techniques to obtain essential 
information. One such technique is 
otolith microstructure analysis (Ste¬ 
venson and Campana, 1992). This 
analysis provides a timeline of the 
life history of individuals, including 
the precise date of hatching, and 
analysis of growth rate and condition 
up to the observed size at capture 
(Campana and Jones, 1992). In fact, 
daily increments can be used not 
only for aging larvae and early juve¬ 
niles, but also for fish that are sev¬ 
eral months old (Fey and Linkowski, 
2006) and sometimes adults (Hiissy 
et a!., 2010). Unfortunately, even 
the most precise analysis based on 
abundant, long-term material will 
be worthless if the underlying data 
are erroneous. The basic information 
that must be verified is daily incre¬ 
ment formation and the time of first 
increment formation (Geffen, 1992; 
Campana, 2001). Obviously, such 
evaluations should be performed sep¬ 
arately for each species and otolith 
type (i.e., sagittae and lapilli). How¬ 
ever, even within the same species, 
otolith microstructure and frequency 
of increment deposition can vary de¬ 
pending on environmental variables 
and larval growth rates (Campana, 
1963; Folkvord et al., 2000; Fukuda 
et al., 2009). Moreover, preparation 
technique (e.g., with a sagittal view 
with or without polishing, or with a 
transverse section with one or both 
sides polished, etc.) should be consid¬ 
ered because the choice of prepara¬ 
tion technique can affect the accu¬ 
racy and precision of age estimates 
(Fey et al., 2005). Finally, as it was 
recently shown by Fey (2018) for lar¬ 
val Baltic herring (Clupea harengus 
membras ), even the preservation of 
ichthyoplankton samples in alcohol 
may affect otolith quality and the 
results of age-determination and 
growth-rate analysis. 
Several methods can be used for 
