135 
National Marine 
Fisheries Service 
NOAA 
Fishery Bulletin 
@& established in 1881 -«< 
Spencer F. Baird 
First U.S. Commissioner 
of Fisheries and founder 
of Fishery Bulletin 
Abstract—Climate variability is a 
major cause of changes in marine eco- 
systems, including changes in both the 
environment and in many fish species. 
Understanding the factors influencing 
key biological characteristics, such as 
growth, is important for commercially 
targeted species because these charac- 
teristics are used in stock assessments 
that inform fisheries management. 
In this study, otoliths were used to 
examine the growth rates and growth 
chronologies of 2 commercially tar- 
geted small pelagic fish species, the 
common jack mackerel (7rachurus 
declivis) and redbait (Emmelichthys 
nitidus), from 2 regions of southeastern 
Australia. Both species grew larger off 
Kangaroo Island (common jack mack- 
erel: asymptotic length [L,.]=299.40; 
redbait: L=259.79) than off southern 
New South Wales (common jack mack- 
erel: L,.=249.52; redbait: L=238.89). 
Temporal growth synchrony in both 
species and regions (0.17—3.50%) was 
low compared with that of more-site- 
attached benthic species. Interannual 
variations in growth rates of common 
jack mackerel off Kangaroo Island were 
positively correlated with sea-surface 
temperature (SST), with growth rates 
18% higher at 18.0°C than at 16.4°C. 
However, growth was not correlated 
with SST or chlorophyll-a concentra- 
tion for the other species and locations. 
Developing a more complete under- 
standing of the environmental drivers 
of growth in these small pelagic fish 
species may require chronologies to be 
extended and extrinsic variables in the 
models to be increased. 
Manuscript submitted 28 October 2020. 
Manuscript accepted 8 July 2021. 
Fish. Bull. 119:135—148 (2021). 
Online publication date: 4 August 2021. 
doi: 10.7755/FB.119.2-3.4 
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. 
Using otolith chronologies to identify extrinsic 
drivers of growth of 2 commercially targeted 
small pelagic fish species 
Joshua D. Dennis (contact author)! 
Gretchen Grammer”? 
Tim Ward? 
Jonathan Smart? 
Charlie Huveneers' 
Email address for contact author: josh.dennis@flinders.edu.au 
" College of Science and Engineering 
Flinders University 
GPO Box 2100 
Adelaide, South Australia 5100, Australia 
? Aquatic Sciences Research Division 
South Australian Research and Development Institute 
P.O. Box 120 
Henley Beach, South Australia 5022, Australia 
3 School of Biological Sciences 
The University of Adelaide 
Adelaide, South Australia 5005, Australia 
Small pelagic fish species are a diverse 
group of marine species that form large, 
mobile epipelagic schools and consti- 
tute the majority of the vertebrate 
biomasses in most open-water eco- 
systems (Agenbag et al., 2003; Fréon 
et al., 2005). They form a pivotal link 
between upper and lower trophic lev- 
els, facilitating energy transfer from 
plankton to predators, such as marine 
mammals, seabirds, and large fish spe- 
cies (Essington et al., 2015). Disruption 
or alteration of this link can have broad 
effects on marine ecosystems (Essington 
et al., 2015). Small pelagic fishes also 
support some of the largest fisheries in 
the world. For example, the fishery that 
targets Peruvian anchoveta (Engrau- 
lis ringens) in the Humboldt Current 
is responsible for Peru having one of 
the largest total marine catches in the 
world (FAO, 2018). 
Somatic growth of small pelagic fishes 
is highly variable and related to their 
reproduction, abundance, movement 
patterns, and mortality (Rountrey et al., 
2014; Lorenzen, 2016). For example, the 
growth of the Atlantic horse mackerel 
(Trachurus trachurus) varies across 
its distribution, with growth rates and 
length at maturity increasing with lati- 
tude (Abaunza et al., 2008). Understand- 
ing drivers of growth variation is crucial 
for determining how the population 
dynamics of small pelagic fishes may 
vary over space and time (Doubleday 
et al., 2015; Smolinski, 2019). Predicting 
how populations will adapt to environ- 
mental changes and adjusting fishing 
strategies accordingly will help prevent 
overfishing (Black, 2009). For example, 
dominant regime shifts between sardine 
(Sardinops spp.) and anchovy (Engrau- 
lis spp.) species have been attributed to 
differences in the optimum tempera- 
ture for growth (Lindegren et al., 2013), 
influencing future fish stocks and fish- 
eries development (Koenigstein et al., 
2016). 
Age and growth are key character- 
istics in fisheries research and critical 
components of age-structured popu- 
lation models (Fournier et al., 1998). 
Growth chronologies of fish species 
