Use of specific bacterial-microalgal biofilms for improving the larval settlement of Argopecten purpuratus (Lamarck, 1819) on three types of artificial spat-collecting materials Yanett E. Leyton 1 , Carlos E. Riquelme ⁎ Department of Aquaculture, Marine Resources Faculty, University of Antofagasta, Casilla 170, Antofagasta, Chile Received 3 July 2007; received in revised form 28 January 2008; accepted 28 January 2008 Abstract In hatcheries of Argopecten purpuratus it is a common practice to harvest the larvae in collectors covered with a coat of microbial biofilm to promote larval settlement. The biofilm coating is obtained by immersion of the collectors for a few days in seawater prior to its use in a process called “pre-conditioning”. The present study was an attempt to evaluate the pre-conditioning process of exposing three different brands of imported and locally produced collector materials (“Netlon”) to biofilms formed by the bacterium Halomonas sp. and the diatom Amphora sp. The results showed the highest degree of settlement of larval scallops on mature biofilms (90 + h), but there were no significant substrate Netlon-dependent differences. Tests with Chilean-produced Netlon seeded with varied concentrations of Halomonas sp./Amphora sp. promoted settlement of the larval scallops better than naturally deposited microbial films. Future research is required to determine more precisely what substances or physical characteristics of the biofilms are effective in inducing larval settlement. © 2008 Elsevier B.V. All rights reserved. Keywords: Argopecten purpuratus; Larval settlement; Specific biofilms; Netlon 1. Introduction Mass hatchery culture of the Chilean scallop Argopecten purpuratus requires the settlement of mature larvae into “spat” collectors which can be taken to sea for out-culture. Japanese plastic netting material termed Netlon® (Inversiones Tecnonet LTDA), traditionally used for capture of scallop larvae in the sea, was found to be useful as collectors for larval scallops produced in hatcheries. Due to the high cost of this material imported from Japan, more cost-effective alternate sources of comparable netting (all termed “Netlon” in Chile, including Chinese and Chilean products) have been locally employed in the culture process (Narvarte, 2001). Empirical studies showed that spat collection was improved by pre-conditioning the Netlon in the sea for a few days, during which the material acquired primary fouling of bacteria, diatoms, and protozoa. The microbial film formed on benthic surfaces may serve as food for newly settled scallop larval–postlarval stages (Avendaño-Herrera et al., 2002). Microfouling of setting substrates under uncontrolled conditions is a highly variable and ill-defined process due to natural envi- ronmental variation. Suzuki et al. (1997) stipulated that the highly variable nature of biofilms consisting of diatoms and associated microflora represented a “black box” which produced irregular scallop settlement patterns. In addition, Kreft et al. (2001) postulated that substrate texture was one of the deter- mining factors in microbial settlement and primary film for- mation on surfaces immersed in the sea. Due to the preceding, it was important to know which microorganisms within the biofilms were favorable to the settlement of larval A. purpuratus. Previous study noted the existence of bacteria and diatoms on larval scallop collectors which may have stimulated settle- ment of the larvae (Avendaño-Herrera et al., 2002). Some Available online at www.sciencedirect.com Aquaculture 276 (2008) 78 – 82 www.elsevier.com/locate/aqua-online ⁎ Corresponding author. Tel.: +56 55637447, +56 55637140; fax: +56 55637804. E-mail addresses: yleyton@uantof.cl (Y.E. Leyton), criquelme@uantof.cl (C.E. Riquelme). 1 Tel.: +56 55637447, +56 55637140; fax: +56 55637804. 0044-8486/$ - see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.aquaculture.2008.01.037