Predation of hatchery-reared scallop spat (Pecten maximus L.) by the
Ballan wrasse (Labrus bergylta)—consequences for sea ranching
Tore Strohmeier
a,
⁎
, Guri G. Oppegård
b
, Øivind Strand
a
a
Institute of Marine Research, Shellfish Research Group, Nordnes gt. 50, N-5024 Bergen, Norway
b
University of Bergen, PB 7800, N-5020 Bergen, Norway
Received 7 April 2005; received in revised form 28 September 2005; accepted 30 September 2005
Abstract
Fish predation on scallops has received relatively little attention compared to the primary predators sea stars and crabs.
Available knowledge of fish predation is mainly based on observations from scallop beds and fish stomach analysis. These are the
first controlled experiments conducted to test if fish (Ballan wrasse, Labrus bergylta) prey upon on hatchery-reared scallop spat.
Under laboratory conditions Ballan wrasse from 22 to 40.5 cm in length were offered spat from 15 to 34 mm in shell height at a
density of 50–103 individuals m
− 2
. Predation was recorded in 15 out of 35 tanks. The mean predation frequency for all tanks was
0.10. The mean predation frequency for the 15 predation tanks was 0.17 and the mean size class predation frequency was 0.53 (15–
19 mm), 0.16 (20–24 mm), 0.03 (25–29 mm) and 0 (30–34 mm) (n =15). The mean predation frequency was significantly
different between spat of 15–19 and 20–24 mm in shell height. No significant difference in predation frequency was found
between larger spat. There was also indication of size-dependent predation from a field experiment, although this experiment was
not conclusive. Results from this study indicate that farmers may seed spat larger than 30 mm in shell height for sea ranching with a
minor risk of predation from Ballan wrasse.
© 2005 Elsevier B.V. All rights reserved.
Keywords: Ballan wrasse (Labrus bergylta); Great scallop (Pecten maximus); Sea ranching; Size dependent predation
1. Introduction
Fish predation on scallops has received relatively
little attention compared to the primary predators sea
stars and crabs. Knowledge of fish predation is mainly
based on observations from scallop beds and fish stom-
ach analysis (Spencer, 1991; Stokesbury and Himmel-
man, 1995; Irlandi and Mehlich, 1996; Vacchi et al.,
2000; Naidu, 2003; Strand, in press). We describe the
first controlled experiments conducted to test if fish
(Ballan wrasse, Labrus bergylta) prey upon hatchery-
reared scallop spat.
Sea ranching of scallops (Pecten maximus) in Norway
has been associated with great losses due to predation by
the edible crab (Cancer pagurus)(Bergh and Strand,
2001). This predation is now limited by the development
and utilization of fencing that prevents intrusions of
crabs, which has resulted in high survival of scallops in
sea ranching (Strand et al., 2002). Since crab predation is
significantly reduced, the opportunity of seeding smaller
scallops directly from hatchery to bottom culture has
emerged. A direct release of scallops from the hatchery
will greatly reduce the labour effort and cost associated
with operation of intermediate culture.
Aquaculture 254 (2006) 341 –346
www.elsevier.com/locate/aqua-online
⁎
Corresponding author. Tel.: +47 55236897; fax: +47 55235384.
E-mail address: tore.strohmeier@imr.no (T. Strohmeier).
0044-8486/$ - see front matter © 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.aquaculture.2005.09.029