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. Linnane et al. J. Exp. Mar. Biol. Ecol. 249 2000 51 –64
1. Introduction
Most benthic marine invertebrates have a complex life cycle involving a pelagic dispersal phase followed by settlement onto a preferred substratum associated with their
early benthic phase EBP habitat reviewed by Chia and Rice, 1978; Burke, 1983; Crisp, 1984; Morse, 1985; Svane and Young, 1989. The duration of this phase can
extend from a few minutes to several months, depending on the species Mileikovsky, 1971; Scheltema, 1986. Where a suitable site is absent or under conditions unfavourable
to subsequent survival and growth, many species have the ability to prolong planktonic life, thereby demonstrating an important degree of selectivity for the settlement
substratum Grosberg, 1981; Botero and Atema, 1982; Cobb et al., 1983; Petersen, 1984; Young, 1989; O’Conner, 1991. Whereas the larval form of the European lobster
Homarus gammarus has been identified in nature Tully and O’Ceidigh, 1987, the benthic habitat to which it recruits to remains largely unknown.
Several laboratory studies have examined the substratum preferences of EBP lobsters and many have revealed the animals’ ability to utilise a wide range of
habitats of varying structural complexity ranging from unsieved mud to macroalgal covered rocks Berrill, 1974; Howard and Bennett, 1979; Botero and Atema, 1982;
Pottle and Elner, 1982; Barshaw and Bryant-Rich, 1988; Boudreau et al., 1993. However, up to the end of the 1980s there were few quantitative descriptions of
newly recruited lobsters in nature Hudon, 1987; Able et al., 1988 as conventional benthic sampling methods such as cores and grabs were unsuitable for gravel and
cobble substrata, areas believed to be prime nursery areas for EBP lobsters. This problem was addressed with the development of the airlift suction sampler Incze and
Wahle, 1991; Wahle and Steneck, 1991. The device was first tested in the United States and proved considerably successful in identifying benthic recruitment habitats
and nursery grounds of EBP American lobster Homarus americanus within the coastal Gulf of Maine. Here, juveniles were seen to be restricted to the shelter
providing habitat of cobble substratum Wahle and Steneck, 1991 where average
2
population densities were as high as 6.9 individuals m . In 1994, a sampling study was undertaken in the west and southwest coasts of
Ireland and the Channel Islands, UK, in order to gain some insight into the habitat requirements of EBP European lobsters. To date, there are no published reports of
newly settled European lobsters in the wild. Despite being unable to locate juvenile lobsters, the study revealed that the species diversity within cobble habitats in Ireland
and the Channel Islands is high, with reptant decapods such as squat lobsters galatheidae, porcelain crabs porcellanidae, mud crabs xanthidae and snapping
shrimp alpheidae appearing to dominate Wahle, 1998. This is in direct contrast to the American situation, where in the Gulf of Maine the diversity is relatively low
with Homarus americanus and the rock crab Cancer irroratus being by far the two most abundant species.
This study aimed to elucidate where juvenile European lobsters may spend their early benthic life by quantifying the settlement of postlarvae onto four types of substratum and
monitoring their substratum preference over a 9 month period.
A . Linnane et al. J. Exp. Mar. Biol. Ecol. 249 2000 51 –64
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2. Materials and methods
