Author:
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Condal, Fernando; Aguzzi, Jacopo; Sardà Amills, Francesc; Nogueras Cervera, Marc; Cadena Muñoz, Francisco Javier; Costa, Corrado; Río Fernandez, Joaquín del; Manuel Lázaro, Antonio
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Abstract:
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To adequately describe seasonal rhythms in
habitat utilization by fish communities, observations are
needed that occur at a relatively high frequency and over
large temporal windows. For the first time, images collected
from a cabled video-observatory (the western
Mediterranean expandable SEAfloor OBservatory; OBSEA)
were utilized to examine habitat utilization by coastal
fishes. Over the course of a year, hourly digital images of
the water column and an artificial reef were obtained during
daylight hours. For each image, the total number of
species, an estimate of the abundance of individuals, and
the Shannon Diversity Index were quantified. A total of 22
fish species commonly associated with nearshore western
Mediterranean habitats were identified, and significant
spatial (water column vs. artificial reef), seasonal (spring,
summer, autumn, and winter), and daily (morning, midday,
and sunset) differences in habitat utilization occurred. Four
species (Diplodus vulgaris, Diplodus cervinus, Diplodus
sargus, and Scorpaena porcus) were associated with the
artificial reef, while one species (Pagrus pagrus) chiefly
occurred in the water column. Chromis chromis and
Diplodus annularis occurred at the site more frequently in
the winter and autumn, respectively, while 14 other species
utilized the site more frequently in either the spring (8 spp)
or summer (6 spp). In addition, Dentex dentex and Spicara
maena occurred more frequently at sunset, while D. cervinus
displayed a crepuscular rhythm (occurring more
frequently in the morning and at sunset). Species diversity
was highest in the summer and lowest in the winter. If not
taken into account when planning in situ sampling, such
seasonal and/or diel differences may lead to spurious
estimates of population sizes and biodiversity. We suggest
that cabled video-observatories offer a non-invasive and
reliable technology for faunistic sampling and population
assessment in coastal water of the Mediterranean and likely
elsewhere. |