Integrated Multitrophic Aquaculture: Filter Feeders Bivalves as Efficient Reducers of Wastes Derived from Coastal Aquaculture Assessed with Stable Isotope Analyses - Aquaculture and the Environment: A Shared Destiny - page 106

Fig. 1. Map of the SW coast of Mallorca. Solid circles indicate sampling sites (Cage: cage site,
C1: control 1, C2: control 2).
Filter feeder bivalves Mytilus galloprovincialis and Chlamys varia were chosen for this study as
they are native to the region, fast growing and commercially viable. They were collected
from the harbor area in Andratx Bay between April and July 2007 and transferred to
polyethylene plastic bags (0.70 x 0.40 m and 0.009 m mesh diameter) with a density of 250
Mytilus galloprovincialis /bag (size between 44 and 72 mm) and 100 Chlamys varia /bag (size
between 19 to 42 mm). Forty plastic bags were placed hanging on fish cages, and the same
amount was simultaneously attached to the rope buoys in control 1 and control 2.
2.2 Sampling and data collection
2.2.1 Cage site
In the experimental site (hereafter called cage site), approximately 10 adult specimens of
Argyrosomus regius , and 6 samples of Mytilus galloprovincialis and Chlamys varia (Linnaeus,
1758) were sampled seasonally. Additionally, potential food sources derived from aquaculture
wastes as fish faeces and pellet and fresh food were sampled; as well as the other components
of the marine food web, phytoplankton, zooplankton, particulate organic matter (POM) and
sedimentary organic matter (SOM). Moreover, 5 sedimentivorous echinoderms Holothuria
forskalii Delle Chiaje, 1823 were also collected.
Fish faeces were collected using pipettes after transferring adult Argyrosomus regius in a
conical tank for an overnight evacuation. Individuals were then sacrificed in order to extract
the muscle tissue from the left side of the posterior region to the dorsal fin using stainless-
steel tools, then, samples were cleaned thoroughly and rinsed with distilled water.
Phytoplankton and zooplankton samples were collected using a plankton net (100 μm mesh
size, 30 cm diameter) and a WP2 plankton net for zooplankton (250 μm mesh size, 45 cm
diameter), respectively, which were towed through the water subsurface for 15 minutes at a
velocity of 2 knots.