360 
Food habits and energy values of prey 
of striped marlin, Tetrapturus audax, 
off the coast of Mexico 
Leonardo A. Abitia-Cardenas* 
Felipe Galvan-Magana 
Departamento de Pesqueriasy Biologia Marina. 
Centro Interdisciplinario de Ciencias Marinas, IPN. 
Apdo. Postal 592. La Paz, Baja California Sur, Mexico. C.P 23000 
*E-mail address. Iabitia@vmredipn.ipn.mx 
Jesus Rodriguez-Romero 
Centro de Investigaciones Biologicas del Noroeste, S.C. 
Apdo. Postal 128. La Paz, Baja California Sur, Mexico. C.P 23000. 
The waters off the tip of the Baja 
California peninsula are good fish- 
ing grounds for striped marlin, 
Tetrapturus audax (Squire and 
Suzuki, 1990) because they offer a 
shallow thermocline and an abun- 
dant food supply (Hanamoto, 1974). 
Although striped marlin are an 
important game fish, few biological 
studies have been done on them. 
Most trophic studies on marlin spe- 
cies have simply identified and de- 
termined the relative importance of 
food consumed in a given geo- 
graphic region and were based on 
few samples (Morrow, 1952; Hubbs 
and Wisner, 1953; Yabuta, 1953; La 
Monte, 1955; de Sylva, 1962; Will- 
iams, 1967; Koga, 1968). 
Only two studies have been done 
off the coast of Mexico in the Pa- 
cific Ocean. Evans and Wares 
(1972) described the stomach con- 
tents of striped marlin caught at 
three locations off southern Califor- 
nia and Mexico (San Diego, Ma- 
zatlan, and Buenavista) from 1967 
to 1969. They found in Buenavista, 
the site closest to our study area, 
that the food for marlin consisted 
mainly of squid and fish, particu- 
larly red-eye round herring (Etru- 
meus teres ) and chub mackerel 
(Scomber japonieus). In the second 
study, Eldrige and Wares (1974) de- 
scribed food habits, seasonal abun- 
dance, and parasites of striped mar- 
lin caught in 1970 near the same lo- 
cations. The differences found, in 
comparison with the first study were 
the absence of S. japonieus and a 
greater importance for three fish spe- 
cies: E. teres , black skipjack (Euthyn- 
nus lineatus ), and oceanic puffer 
(Lagocephalus lagoeephalus). 
This paper provides information 
on food habits and energy content 
of the principal prey consumed by 
striped marlin in waters off the 
coast of the Baja California penin- 
sula, Mexico. 
Materials and methods 
Striped marlin were caught by 
trolling with live chub mackerel, S. 
japonieus, and jacks, Caranx spp., 
as bait or by jigs used by the sport 
fishing fleet. All fish were collected 
at approximately 22° 53'N, 109°54'W 
(Fig. 1) near Cabo San Lucas, Baja 
California Sur (B.C.S.), Mexico. 
Stomachs were sampled in port, 
May 1988 to December 1989, by 
personnel of the Centro Inter- 
disciplinario de Ciencias Marinas 
(CICIMAR), La Paz, B.C.S. Each 
fish was weighed to the nearest kg 
and its length (eye fork length) 
measured to the nearest cm. Stom- 
ach contents were removed and 
fixed in 10% formalin. Prey were 
identified to the lowest possible 
taxon. Vertebral characteristics 
(e.g. number, position) were used to 
identify fish with the help of taxo- 
nomic keys (Clothier, 1950; Monod, 
1968; Miller and Jorgensen, 1973). 
The fish collection of CICIMAR was 
also used for comparison and valida- 
tion of identifications. For complete, 
undigested fish, the keys of Jordan 
and Evermann (1896-1900), Meek 
and Hildebrand (1923-28), Miller 
and Lea (1972), and Thomson et al. 
(1979) were used for identification. 
Crustacean prey were identified from 
exoskeleton remains with keys pro- 
vided by Garth and Stephenson 
(1966) and Brusca (1980). Cephalo- 
pods were identified from mandibles 
with the keys of Clarke ( 1962, 1986), 
Iverson and Pinkas ( 1971), and Wolff 
(1982, 1984). 
The stomach contents were enu- 
merated (A0 and the volume (VO mea- 
sured to the nearest mL. These two 
measures and frequency of occur- 
rence (FO) were combined to calcu- 
late the index of relative importance 
(IRI) of Pinkas et al. (1971) as 
IRI = (%N + %V) %FO. 
IRI is a commonly used measure 
that provides a more representative 
summary of dietary composition 
(Caillet et al., 1986). 
A multivariate analysis of vari- 
ance (MANOVA) was made on IRI 
values to examine differences in the 
relative importance of prey by sea- 
son and between species. The treat- 
ment included only five seasons 
because the data in two seasons 
(summer and fall 1989) had too few 
values for statistical analysis 
(Table 1). The data were standard- 
ized following the formula 
Manuscript accepted 4 November 1996. 
Fishery Bulletin 95:360-368 (1997). 
