The Role of Kelp in the Marine Environment - National Parks ...

Jorgensen and Christie, 2003; Christie et al., 2003). Mobile macrofauna (particularly
crustaceans and molluscs) are important in the diet of many fishes and their
abundance in the kelp forest makes this habitat a rich source of prey for many top
down predatory consumers (Jorgensen and Christie, 2003; Christie et al., 2003).
Christie et al. (op. cit.) estimated that an average density exceeding 100,000 mobile
macrofauna individuals per m 2 could be expected in a Norwegian L. hyperborea kelp
forest.
Variation in abundance of prey taxa and faunal groups may be reflected in the diet of
some kelp fish species. For example, amphipods and gastropods were found to be the
dominant faunal groups in studies of recovering and natural kelp forests in Norway
(Moore, 1972; 1973; Schultze et al., 1990; Christie et al., 1998; 2003; Norderhaug et
al., 2002). Correspondingly, these groups have been found to be dominant in the diet
of various fish species associated with kelp habitat (Gordon, 1983; Fossa, 1995; Fossa
et al., 1998; Fredriksen, 2003). Other studies have noted opportunistic tendencies in
wrasse species with respect to variation in prey availability, with seasonal and
temporal changes in the abundance of prey species reflected in the diet (Deady, 1995;
Deady and Fives, 1995ab; Varian, 1998; Zemke-White and Clements, 2004).
There may also be some interspecific variation between kelp species in the foraging
opportunities available to fishes. According to Schultze et al. (1990), the diversity
and abundance of macroinvertebrates is higher in Laminaria hyperborea beds than in
L. digitata stands. Invertebrate abundance has also been related to the age and size of
the plant within kelp species. For example, Rinde et al. (1992) found that the number
of individuals and species of kelp-associated flora and fauna increased significantly
with increasing age of kelp plants. Thus, the availability of macroinvertebrates as
food items for kelp fishes may depend to an extent on the species and age of kelp
plants distributed within the kelp habitat.
Some Norwegian studies have considered the importance of fish in the trophic
structure of the kelp forest ecosystem, i.e., as prey for seabirds and other fish (Røv et
al., 1990; Lorentsen et al., 2004) and as top down predators and consumers of
invertebrate fauna (Nelson, 1979; Kennelly, 1983, 1991; Holmlund et al., 1990;
Nordeide and Fossa, 1992; Fosne and Gjosaeter, 1996; Fredriksen, 2003). Røv et al.
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