Page 3 - Bracciali_2016

118 C. Bracciali et al. / Marine Environmental Research 113 (2016) 116e123
Table 1
Features and range of values recorded from March to August in LOW-HYDRO site of sheltered and shallower Cammello Bay and deeper and opener HIGH-HYDRO site of Punta
Bassana (CHL-a ¼ chlorophyll-a, Pheo ¼ pheopigment, TSM ¼ total suspended matter, ISM ¼ inorganic suspended matter, OSM ¼ organic suspended matter).
Site characteristics LOW HYDRO HIGH HYDRO
LAT 37 59 00 00 37 56 59 00

0

0
LONG 12 03 56 00 12 05 23 00

0
0

Site description http://www.parks.it/indice/iti_dettaglio.php?id_iti¼2068 http://www.parks.it/indice/iti_dettaglio.php?id_iti¼2061
Exposition north-east south-east
Depth (m) 20 40
Bottom slope gradual steep
Bottom cover sand covered by P. oceanica mixed to rocky reef sand covered by P. oceanica mixed to rocky reef
Temperature ( C) 13e25.5 12e24

CHL-a (mgl 1 ) 0.12e0.26 0.08e0.12
Phaeo (mgl 1 ) 0.05e0.23 0.02e0.10
TSM (mg l 1 ) 6.93e9.68 5.10e13.45
ISM (mg l 1 ) 5.37e7.22 3.43e10.20
OSM (mg l 1 ) 1.57e2.47 1.67e3.25
Hydrodynamics (source: http://marine.copernicus.eu)
Winter 11.9 ± 4.4 15.2 ± 3.3
Spring 7.1 ± 2.5 19.9 ± 5.7
Summer 6.6 ± 3.6 20.6 ± 6.6
Autumn 14.9 ± 5.8 13.3 ± 2.2
Year 10.1 ± 4.9 17.2 ± 5.2
composition to phytoplankton on which they rely and show TpsDig 2 software (http://life.bio.sunysb.edu/morph/).
negative correlation with chlorophyll-a concentration due to their
grazing (Calbet et al., 2001); (iii) higher current velocities should 2.3. Data analyses
result in higher rates of food supply (amount per unit time e sensu
Sar a and Mazzola, 2004). Thus, accordingly, damselfish of the To test whether different hydrodynamics generated changes in
HIGH-HYDRO sites should be exposed to higher amount of food per functional trait's with potential repercussions on life history traits,
time unit than LOW-HYDRO co-specifics (Table 1) at only few kms we used some descriptors of growth performance that are classi-
one each other. cally adopted in fish biology as follows.
2.3.1. Allometry and body condition
2.2. Fish sampling and processing
The length-weight relationship was described by the following
allometric equation (Gould, 1966; Dulcic and Kraljevic, 1995):
Damselfish were later collected, from March to July 2007. Four b
samplings (n ¼ 4) were carried out at regular intervals, approxi- TW ¼ a *SL which was linearized through base 10 logarithms).
The parameter b in the linearized form was taken as an allometric
mately every 40 days, at both the LOW- and HIGH-HYDRO sites.
Specimens were collected with a 1 cm mesh seine net (50 6m) coefficient which usually ranges around 3 in most organisms (sensu
Gould, 1966). Differences in length-weight relationships were
deployed for three replicate hauls from a small fishing boat at the
same depth (about 9e12 m) and at the same time (between 10h00 tested by comparing slopes of allometric regressions (ANCOVA; Zar,
1999; Sar a and Mazzola, 2004). The Body Condition Index (BCI;
and 13h00 GT). For each seine haul, the total number (N) of Nash et al., 2006; Bracciali et al., 2012) per each SL class (SLc; 5 mm
C. chromis captured were recorded directly on-board. All in- each) was computed as follows: BCI ¼ TW/SL . Differences in BCI
3
dividuals collected were frozen at 20 C in the field and trans- were tested by ANOVAs (Zar, 1999) according to SL (7 levels; 5 mm

ported back to the University of Palermo Experimental Ecology
steps) and hydrodynamics (2 levels: low vs. high). When the vari-
laboratory for further examination. Once in laboratory, for each ance was not homogeneous tested through the Cochran's C test (i.e.
individual fish, standard length (SL) was measured with a Vernier
caliper (nearest to 0.05 mm), and total wet weight (TW) with a p < 0.05), we did not transform it but we lowered the significant
value level from a ¼ 0.05 to 0.01 (Ruiz et al., 2010).
Mettler Toledo balance (nearest to 0.1 g). The sagittal otolith was
used to estimate the annual age (y) of a subsample (n ¼ 207 and
n ¼ 164 in LOW- and HIGH-HYDRO, respectively) (Secor et al., 2.3.2. Body growth
1995). Discrimination of light and dark bands (annuli) was made Growth of C. chromis was expressed through a linear growth
with a stereo microscope LEICA EZ 4D (12.5 magnification) with model of length at age (Green et al., 2004; Nyamweya et al., 2010):
reflected light. The whole otolith was positioned in immersion oil LS ¼ a þ b * Age, where the slope b was considered as the growth
on a dark surface to increase the contrast between annuli. Two coefficient. Differences in growth rates between sites were tested
authors independently counted in blind the annuli and agreement by using the ANCOVA (Sar a and Mazzola, 2004).
between readers determined the final age estimate. A subsample of
individuals of a total of 120 individuals (n ¼ 30 in March and n ¼ 30 2.3.3. Body shape
in July from the two studied sites; tot ¼ 120 individuals analyzed) All morphometrics showed a strong correlation with the SL
were chosen randomly to investigate if fish from two hydrody- (Table 2) allowing us to eliminate the individual size effect (Agnese
namics were morphometrically different (Fig. 2). All individuals et al., 1997; Dul ci c, 2005). SL of LOW- and HIGH-HYDRO specimens
were pinned with the fins extended in the standard position and was compared with a T-test. The coefficient of variation (CV) of each
photographed with a compact digital camera CANON Power shot morphometric was calculated. The relationship between the body
fixed on a tripod. The fish measuring board was equipped with a height and the SL was analyzed to assess: i) seasonal differences
ruler as a reference scale and illuminated by a direct light. We between sampling periods within each site; and ii) differences
measured the 16 morphometric traits (Dulcic, 2005 e Fig. 2) using between sites (LOW- vs HIGH-HYDRO) according to the individual