101 
Reconstruction of original body size 
and estimation of altometric relationships 
for the longfin inshore squid ( Loligo pealeii ) 
and northern shortfin squid (///ex iliecebrosus ) 
Michelle D. Staudinger 1 
Francis Juanes 1 
Suzanne Carlson 2 
Email address for contact author: mstaudm@nre.umass.edu 
1 Department of Natural Resources Conservation 
University of Massachusetts Amherst 
Amherst, Massachusetts, 01003-9285 
2 School of Natural Science 
Hampshire College 
Amherst, Massachusetts, 01002 
Quantification of predator-prey body 
size relationships is essential to under- 
standing trophic dynamics in marine 
ecosystems. Prey lengths recovered 
from predator stomachs help deter- 
mine the sizes of prey most influential 
in supporting predator growth and 
to ascertain size-specific effects of 
natural mortality on prey populations 
(Bax, 1998; Claessen et al., 2002). 
Estimating prey size from stomach 
content analyses is often hindered 
because of the degradation of tissue 
and bone by digestion. Furthermore, 
reconstruction of original prey size 
from digested remains requires spe- 
cies-specific reference materials and 
techniques. A number of diagnostic 
guides for freshwater (Hansel et al., 
1988) and marine (Watt et al., 1997; 
Granadeiro and Silva, 2000) prey spe- 
cies exist; however they are limited 
to specific geographic regions (Smale 
et al., 1995; Gosztonyi et al., 2007). 
Predictive equations for reconstruct- 
ing original prey size from diag- 
nostic bones in marine fishes have 
been developed in several studies of 
piscivorous fishes of the Northwest 
Atlantic Ocean (Scharf et al., 1998; 
Wood, 2005). Conversely, morphomet- 
ric relationships for cephalopods in 
this region are scarce despite their 
importance to a wide range of preda- 
tors, such as finfish (Bowman et al., 
2000; Staudinger, 2006), elasmo- 
branchs (Kohler, 1987), and marine 
mammals (Gannon et al., 1997; Wil- 
liams, 1999). 
As with the bones and otoliths of 
prey fish, cephalopod beaks are often 
recovered from predator stomachs 
and may be used for identification of 
prey species and the reconstruction 
of original prey body size (Clarke, 
1986). Many predators (e.g., marine 
mammals) cannot digest the chitin- 
ous beaks and thousands of beaks 
may accumulate in the stomachs 
until they are regurgitated (Clarke, 
1980). Predictive equations for es- 
timating body size in the two most 
common species of cephalopods in the 
Northwest Atlantic Ocean (Bowman 
et al., 2000) are either based on few 
observations (n = 25) as seen in the 
longfin inshore squid (Loligo pealeii) 
(Gannon et al., 1997), or are nonexis- 
tent as is true for the northern short- 
fin squid ( Illex iliecebrosus). 
Trophic niche breadth is the range 
of relative prey sizes consumed onto- 
genetically by a predator (Scharf et 
al., 2000). In previous diet studies, 
trophic niche breadth has been used 
to predict shifts in foraging modes 
and physical limitations on feeding 
patterns (Bethea et al., 2004; Beau- 
champ et al., 2007). Calculation of 
trophic niche breadth requires mea- 
surements of the total lengths of 
predators and prey. Depending on 
how a species is traditionally mea- 
sured (e.g., fork length in fish, man- 
tle length in squid) in population and 
other types of surveys, information 
on total length may not always be 
readily available. Therefore, knowl- 
edge of allometric relationships may 
be useful to accurately assess trophic 
interactions and predator-prey rela- 
tionships. For the majority of ceph- 
alopod species, there are currently 
no predictive equations to estimate 
total length from mantle length and 
to account for variability in growth. 
To improve descriptions of the feed- 
ing habits of teuthophagous preda- 
tors and to increase the number of 
evaluations of size-based predation 
on cephalopod prey we present 1) pre- 
dictive equations for reconstructing 
original prey size and 2) allometric 
relationships of mantle length to 
total body length for the two most 
common species of cephalopods in the 
Northwest Atlantic Ocean, L. pealeii 
and I. iliecebrosus. 
Materials and methods 
Loligo pealeii were collected by otter 
trawl from coastal waters off Mas- 
sachusetts during the months of May 
through September of 2006 and 2007. 
Illex iliecebrosus were collected from 
outer shelf waters from New Jersey 
to North Carolina during February 
2007 on both the winter and spring 
bottom trawl surveys conducted by 
the National Marine Fisheries Ser- 
vice (Northeast Fisheries Science 
Center) (Azarovitz, 1981). All squid 
were preserved by freezing until 
they were processed in the labora- 
tory. Specimens were thawed to room 
temperature and then measured for 
dorsal mantle length (DML), total 
length (TL), and maximum length 
(L Max ) to the nearest 1.0 millimeter. 
Dorsal mantle length was measured 
as the distance between the posterior 
Manuscript submitted 2 June 2008. 
Manuscript accepted 28 August 2008. 
Fish. Bull. 107:101-105 (2009). 
The views and opinions expressed 
or implied in this article are those 
of the author and do not necessarily 
reflect the position of the National 
Marine Fisheries Service, NOAA. 
