Record Details

Studies on major small pelagic fishes along the Kerala Coast with respect to the Potential Fishery Zone (PFZ) advisories

CMFRI Repository

View Archive Info
 
 
Field Value
 
Relation http://eprints.cmfri.org.in/10763/
 
Title Studies on major small pelagic fishes along the Kerala Coast with respect to the Potential Fishery Zone (PFZ) advisories
 
Creator Nair, Preetha G
 
Subject Pelagic Fisheries
Theses
 
Description Indian National Centre for Ocean
Information Services (INCOIS),
Hyderabad, India provides fishery
forecast services all along the Indian
coast free of cost, referred to as
‘Potential Fishery Zone (PFZ)
Advisories’. These services include georeferenced
maps showing marked regions
where probability of finding sizeable
schools of fishes is high. These advisories
are provided to help the fisher folks to
improve their income from fishing by
saving engine fuel for searching and
locating fish stocks. Based on 124 controlled fishing
experiments carried out in the PFZ and
Non-PFZ zones along the Kerala coast
during 2008-2012 periods, the present
study evidenced that commercially
important fishes were abundant in the
PFZ, forming richer fisheries compared to
the non-PFZ areas. The profit from
controlled experiments showed
consistently higher values in the PFZ than
that in the non-PFZ. The highest profit
during the entire controlled fishing
experiments was obtained when the catch
was dominated by relatively high-priced
fishes such as tunas, carangids, seer
fishes and mackerel. Indian oil sardine
was the major single species obtained
during the Northeast Monsoon
(November-February), whereas, Indian
mackerel dominated during the Southwest
Monsoon (June-October) and Spring
Intermonsoon (March – May) periods.
Anchovies were found to dominate only
in two fishing experiments in the entire
study period. The analyses of catch data of the small
pelagic fishes of interest (Indian oil
sardine, Indian mackerel and
Commerson’s anchovy) showed that the
PFZ advisories better predicted the
catches of Indian oil sardine during the
Northeast Monsoon (November-
February) and Indian mackerel during the
rest of the period. Conversely, the catch
data of controlled experiments showed
that PFZ advisory has less efficiency to
support the exploitation of anchovies.
Attempts have been made to outline the
recurrent PFZ along the Kerala coast
based on the advisories generated for the
study period (2008-2012). Altogether
432 PFZ advisories were digitised and
month-wise repeat PFZs have been
demarcated. In general, most of the very
prominent recurrent PFZs were found
within the 50m depth contour. The
highest number of recurrent PFZs was in
December, January and February. On the
other hand, the lowest number of
recurrent PFZs was found in April, May
and June. Plankton components in the diet of
Indian oil sardine, Indian mackerel and
Commerson’s anchovy based on
fortnightly fish samples analysed during a
year period are presented. Coscinodiscus,
Nitzschia, Pleurosigma and Thalassiosira
were found in the gut of Indian oil
sardine almost throughout the year,
whereas microzooplankton was mostly
dominant only during the October –
December period. Coscinodiscus and
Tintinids were predominant in the gut of
Indian mackerel throughout the year.
Furthermore, Thalassiosira, Ceratium,
Dinophysis, Protoperidinium, Pyrophacus
and copepods were also found in the gut
of Indian mackerel almost throughout the
year. The dominant value index showed
the dominance of phytoplankton,
microzooplankton and copepods in the
diet of Indian mackerel throughout the
year, indicating their almost equal
preference for both phytoplankton and
zooplankton. The food items in the gut
content of Commerson’s anchovy showed
characteristic difference from both Indian
oil sardine and Indian mackerel and found
to be a zooplankton feeder predominantly
feeding on copepods, fish eggs,
ostracods, lucifers and tintinids.
The environmental observations based
on monthly field sampling carried out in
two locations (10m and 20m depth
contours) situated off Kochi are
presented. During seven out of nine
observations, PFZ bands were observed
around 10m location. High values of
chlorophyll (> 3mg m-3) were found in
August, September and October, which
could be attributed to the combined effect
of Cochin backwater influx and
upwelling. The seasonal evolution of
hydrographical parameters showed
significantly higher concentration of
nutrients and chlorophyll during the
Southwest Monsoon period compared to
the rest of the sampling. The chlorophyll
concentration was found to be
significantly higher in 10m location
(PFZ) compared to the 20m location
(non-PFZ). The status of the Length-Weight
Relationship (LWR) and condition factor
of Indian oil sardine, Indian mackerel and
Commerson’s anchovy along the Kerala
coast is presented. The LWR of
Commerson’s anchovy is the very first
detailed report from this region. LWR
and condition factor of Indian mackerel
and Oil sardine were not significantly
different from the values reported in the
historical studies, indicating that these
parameters are not affected significantly
by the expected long-term environmental
changes. The results of the growth and maturity
studies of the small pelagic fishes of
interest have been discussed. The
analyses were based on a fortnightly
sampling carried out in two major landing
centres during 2010 – 2011 periods.
The maximum life span of Indian oil
sardine was estimated to be 2.63 years.
Two peaks of recruitment of juveniles to
the fishery were observed; a large peak
during July - August and a small peak in
February - March. The length at first
maturity was calculated as 15.7 cm while
the length at first capture was 15 cm,
suggesting that the peak exploitation of
the species occurs before they attain
sexual maturity. Comparison of the length
at first maturity of oil sardine reported in
historical studies with the present study
shows that only minor variation exists
between the two. The life span of Indian
mackerel is estimated to be 2 years. The
recruitment pattern showed the presence
of mature mackerel all year round.
However, two recruitment peaks of
Indian mackerel were evident; June to
August and February to March with the
highest recruitment in July (28%).
Probability of capture of mackerel
showed higher values (22.43 cm) than
the length at first maturity (17.7 cm)
indicating that their peak exploitation
occurs after attaining sexual maturity. Long-term changes in length at first
maturity of Indian mackerel indicated a
prominent decrease in length in the recent
decade, probably indicating a response to
the long-term environmental changes.
The present study on the growth and
maturity parameters of Commerson’s
anchovy forms the first such study from
Indian waters and the life span of the
species was found to be 3.06 years. Two
recruitment peaks of Commerson’s
anchovy were observed; first during
February – March and a second during
June - July. The probability of capture of
Commerson’s anchovy showed that they
get exposed to maximum exploitation
after they attain maturity. Lack of past
data on length at first maturity of
Commerson’s anchovy from the Indian
coast hindered a possible comparison
with the present data.
 
Date 2015
 
Type Thesis
NonPeerReviewed
 
Format text
 
Language en
 
Identifier http://eprints.cmfri.org.in/10763/1/Preetha%20G%20Nair%20Ph.D%20thesis.pdf
Nair, Preetha G (2015) Studies on major small pelagic fishes along the Kerala Coast with respect to the Potential Fishery Zone (PFZ) advisories. Doctoral thesis, Central Marine Fisheries Research Institute.