International Journal of Marine Science 2015, Vol.5, No.56: 1-5
4
at which 50% of the fish are vulnerable to be captured
by fishermen. This is the average size of fish
vulnerable to be fishing or enter the fishing ground, in
the Poyang Lake through the Yangtze River Waterway.
3.5 Recruitment pattern
The recruitment patterns of
C. nasus
suggested that
there was one main pulse of annual recruitment, in
agreement with the group separation using Bh
-tacharya’s Plot. The major ulse appeared in July (Fig.
4), Compared with historical data, the miniaturization
of the fish was evident and the community age
structure tended to be one fold and low-aged, at the
same time, the resource of
C. nasus
ha
d decreased significantly.
3.6 Relative yield-per recruit (Y′/R) and relative
biomass-per recruit (B′ /R)
The plots of relative yield-per recruit against exploitation
rate (E) fig. 6) indicated that the present exploitation
rates (E
present
) < the maximum exploitation rate(E
max
)
that could be applied for a sustainable exploitation of
fisheries. For
C. nasus
, the plots of relative Biomass-per
recruit against exploitation rate associated with the
relative yield-per recruit against exploitation rate plots
showed that E
present
> E
0.5
(the exploitation rate at
which 50% of biomass of the recruit is fished),
indicating that, at the current rate of exploitation, there
was the threat of over fishing as >50% of biomass-per
recruit was fished.
4 Conclusion
Present study discovered that
C. nasus
composed of
one cohort in a year with supported by the recruitment
patterns of one main pulses annually. The growth
parameters of asymptotic length 40.95 cm, growth
coefficient 0.25 year
-1
and growth performance index
2.62.
C. nasus
from study area had high total mortality
1.58 year
-1
and fishing mortality 1.04 year
-1
. The
exploitation rates 0.66 year-1 indicated over exploitation.
Thus, all of this information would be the valuable
sources for comparison in future, especially when the
conservation and management of this fish stock is to
be made.
Author's contributions
Wu Bin, Fang Chunlin, and Fu Huiyun designed and
conducted the experiments. Fu Peifeng, Zhou Huiming,
Zhang Yanping, He Gang, Wang Sheng collected the
samples and did the meaurement. All authors read and
Figure 3 VBGF and Length Frequency Plot
Figure 4 non-parametric Scoring of VBGF Fit Using ELEFAN I
Figure 5 Length-Converted Catch Curve
Figure 6 Probability of Capture
Figure 7 Recruitment Pattern
approved the final manuscript.
Acknowledgements
The authors wish to thank Hubei Environmental
Monitoring Central Station, ZhangYuan, for the creation
