Basic HTML Version
International Journal of Marine Science 2014, Vol.4, No.20: 183-193
http://ijms.sophiapublisher.com
191
In general, this aquatic system shows low
concentrations of dissolved or suspended organic
matter and little anthropogenic influence, except for
the east-central coast of the gulf, where values are
emphasized in months of heavy rainfall, mainly in
spring. Seasonal and annual averages obtained in this
Gulf have GOOD quality index for fishing use,
according to the Cuban International Standard NC-25
(1999). Although oxygenation of shelf waters reflects
a decrease tendency compared with the results of
Lluis-Riera (1977), is in the range of good quality for
fisheries use.
The spatial and seasonal distribution of hydrological
parameters, have a relationship with the seasonality of
rainfall and evaporation. The biggest instabilities are
showed in spring, while summer usually reflected
better uniformity in its waters. The spatial distribution
shows that the south has the lowest variations and
better hydrological conditions. Coastal areas to the
north and northeast of Guacanayabo´s Gulf showed
greater freshwater influence, therefore, the largest
seasonal variations, which agrees with the views
expressed by Emilsson and Tápanes (1971) and also
by Rodriguez (1983).
The spatial distribution of pink shrimp major catch
areas in the Gulf, as determined by Giménez et al.
(2012), coincide with the areas of greatest stability of
hydrological markers (South-East). At the same time,
lower abundance of the species, is obtained in the
areas of greater variations and instabilities, higher
values of COD and lower values of dissolved oxygen
saturation. In the case of zone II, at the North part of
the gulf, where the dissolved oxygen was high, the
biomass was recovered in 2010 (1.9 t) after the
protective ban. Nevertheless this value was smallest
than the 7.03 t captured in zone III for the same year.
On the other hand, generally speaking, the decrease in
this fishing resource could be tightly related to the
high fishing effort since the last century until the 2007,
when a collapse in pink shrimp was produced.
Although not statistical comparison was made, there
are slight changes in salinity and higher tendency of
decrease of dissolved oxygen when compared with the
literature reported values for previous decades. The
dissolved oxygen was the most variable marker, which
indicates that in this aquatic system, there is a great
alteration in water oxygenation. Those changes in
hydrological markers could be influenced by the loss
of marine vegetation in the coastal area (personal
observation of the first author). Sea grasses are great
promoters of productivity and biodiversity by their
high primary production, and improve the quality of
the marine environment to dampen wave energy and
retain suspended particles in the water, thus improving
transparency (Borum et al., 2004). Those hydrological
changes, together with an over- exploitation of the
marine shrimp, had influence in this negative trend of
the catch of the resource in Guacanayabo´s Gulf.
On the other hand, the difference in the seasonal
variability of hydrological parameters between the
southern and northern region could be a factor
influencing the spatial distribution of the pink shrimp
abundance for each marine region.
3 Data and Methods
Mean monthly series of precipitations (mm) from
1974 to 2009 were used and from 2008 to 2009 of
evaporation (mm) from Meteorological Station in
Manzanillo. From data series, the monthly and annual
mean were determined to establish the seasonal and
inter annual pattern in Guacanayabo’s Gulf. Besides,
annual and monthly means were transformed in
anomalies for a better graphic interpretation.
Marine environment sampling in Guacanayabo’s Gulf
was made through a 17 network points (Figure 1).
Samples were taken
in situ
both at surface (0.50 m)
and bottom (0.50 m from the bottommost) and in all
cases during the lighting day. Monitoring campaigns
were made in 2008-2009 period, with a total of 11
expeditions: three of them in spring (April/May 2008
and May 2009), five in summer (June/July/August
2008 and June/July 2009) and three in autumn
(September/November 2008 and October 2009). Water
temperature (
℃
), salinity (psu) and dissolved oxygen
were measured (mg/L), with a multiparameter probe
HANNA HI 9828 (precision ± 0.01). Surface water
samplings were taken with Van Dorn bottle and were
conserved in 1 L recipients at -20 ˚C and transported
to the laboratory to be analyzed. Chemical Demand
Oxygen (CDO) test were made by the Procedure to
Marine Waters following (FAO, 1975) and expressed
in mg/L.