| Seasonal and interannual variations of oceanographic
conditions off Mangalore coast (Karnataka, India) and their influences
on the pelagic fishery |
| Mangalore coast is well known for its multi-species and multi-gear
fisheries and the fishery and oceanographic features of this region
is a true representation of the Malabar upwelling system. Ten years
of study (1995-2004) of oceanographic parameters has been carried
out from the inshore waters off Mangalore to understand their seasonal
and interannual variations and influences on the pelagic fishery of
the region. Attempt has been also made to understand the influence
of local and global environmental conditions on the alternating patterns
of abundance between the Indian mackerel and oil sardine from the
area. Field and satellite-derived oceanographic data have shown that
coastal upwelling occurs during July-September with a peak in
August resulting in high nutrient concentrations and biological productivity
along the coast. Nearly 70% of the pelagic fish catch, dominated by
oil sardine and mackerel, was obtained during September-December,
during or immediately after the upwelling season. Catches of scombroid
fishes were significantly related to cold Sea Surface Temperature,
while such relationships were not observed for sardines and anchovies.
Significant positive correlations were observed between the ENSO events
(MEI) and seawater temperature from the study area. The extreme oceanographic
events associated with the cold La Nina, which preceded the exceptional
1997-98 El Nino event, were responsible for the collapse of
the pelagic fishery, especially the mackerel fishery along the southwest
coast of India (Malabar upwelling system). Coinciding with the collapse
of the mackerel fishery, oil sardine populations revived during 1999-2000
all along the southwest coast of India. Tolerance of oil sardine to
El Nino / La Nina events and the low predatory pressure experienced
by their eggs and larvae due to the collapse of mackerel population
might have resulted in its population revival.
(P. K. KRISHNAKUMAR and G. S. BHAT, Fisheries Oceanography 17:1,
45-60, 2008)
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| Impact of Climate Change on Indian Marine Fisheries |
| Climate change is projected to cause massive changes in the environment
which are on a scale unprecedented in the last 1,000 years. The causative
factors of climate change are the greenhouse gases, viz., carbon dioxide,
methane, ozone and nitrous oxide. The most confident projections on
the fall-out of climate change are for the amount of warming and changes
in precipitation. The 20th century is the warmest century in 1,000
years, the 1990s the warmest decade, and 1998 and 2004 the warmest
years. The relatively steady warming in the 20th century increased
the mean temperature by 0.6o C. However, the projections from global
warming models indicate that we may see nearly continuous warming
of about 0.5o C per decade for every decade of this century. Thus
each coming decade may successively add nearly as much warming as
the entire 20th century.
Considering the enormity of the problem and the need to address
the issues connected with climate change and marine fisheries including
sea food security and livelihood, the CMFRI has taken up a major
ICAR Network Project entitled “Vulnerability of Indian Marine
Fisheries to Climate Change”. Preliminary results from this
project indicate that the distribution of fish species with more
rapid turnover of generations may show the most rapid demographic
responses to temperature changes. The distribution of the oil sardine
Sardinella longiceps, for instance, has responded markedly to increase
in sea temperature. With the northern latitudes becoming warmer,
the oil sardine, which is essentially a tropical species, is able
to establish itself in the new territories and contribute to the
fisheries along the northwest and northeast coasts of India.
The strategies adopted by other fish groups are also becoming evident.
Some pelagic species such as the Indian mackerel Rastrelliger kanagurta
show shift in the depth of distribution and are now caught by bottom
trawlers. Demersal species such as threadfin bream Nemipterus japonicus
appear to shift the month of peak spawning toward colder months
off Chennai. There are also indications, which show that copepod
abundance is shifting toward colder months off Mangalore. These
findings indicate that the adaptable species may be able to adjust
to the immediate challenge of rise in temperature for a shorter
or longer duration. On the other hand, the vulnerable groups such
as the corals are in peril. It is found that extensive coral bleaching
occurred in Gulf of Mannar and Andaman and Lakshadweep Seas when
the SST was 31oC or more in 1998 and 2002. The intensity of bleaching
was directly related to the number of days the higher temperature
prevailed.
These initial results emphasize the need for finding answers to
several questions. What will be the influence of rising seawater
temperature on the Bombay duck, whose northern boundary is landlocked?
The distribution and migration of oceanic tunas, which are influenced
by thermocline, may be strongly influenced. The sex of sea turtles
is critically determined by the soil temperature at which the embryo
develops. Temperature above 28o C produces only females. How the
turtles would adopt to this crisis? Will there be species succession
of phytoplankton with the domination of temperature tolerant species?
Is the massive intrusion of pufferfish and medusae into the Indian
coastal waters in recent years a fall out of climate change?
It is much more difficult to project how populations will behave
under radically different conditions. Under these conditions, fisheries
stock assessment, already difficult, may prove impossible. Fisheries
management will likely become far more contentious because the abundance
of fish populations and the composition of communities will change
in unexpected ways.
|
(Extract of article by E. Vivekanandan in CMFRI Newsletter 112: Oct-Dec
2006; http://203.200.148.2/cdhome/Newsletter/Number_112_2006 )
Production of Designer Mabe Pearls in the Black-lipped Pearl Oyster,
Pinctada margaritifera, and the Winged Pearl Oyster, Pteria penguin, from
Andaman and Nicobar Islands
Production of designer mabe pearls (value added
pearls) of images of various shapes in the black-lipped pearl oyster,
Pinctada margaritifera, and the black winged pearl oyster, Pteria penguin,
from the Andaman and Nicobar Islands is described. The production protocol
is elucidated including the dosage of anesthetic to be used for each species,
the position on the shell for fixing the image, the grow-out containers,
and the culture period. The images were introduced into the oysters by
two methods viz., mantle cavity insertion (MCI) into the anterior-dorsal
region or by pasting them on the ventral regions of the inner nacreous
surface of the valves using a commercial cyanoacrylate based commercial
glue. Large P. margaritifera with dorso-ventral measurement (DVM) of 101.0
± 10.3 mm can be fully relaxed by 375 ppm menthol within 120 min
and small oysters of 72.1 ± 5.8 mm by 250 ppm within 95 min. P.
penguin of DVM 96.5 ± 17.9 mm can be completely anesthetized by
145 ppm of menthol within 75 min to facilitate base image implantation.
Good quality mabe pearls were obtained
in 60 days. Gluing was found to be more effective than MCI with potential
for multiple mabe production.
(V. Kripa, K.J. Abraham, C.L. Libini, T.S. Velayudhan, P. Radhakrishnan,
K.S. Mohamed and M.J. Modayil, Journal of the World Aquaculture Society,
March 2008)
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