Dapeng Bay is a typical offshore fisheries area in the South China Sea (SCS). In order to understand the fishery resources, seasonal variations of species composition, dominant species composition, standardized catch per unit effort (SCPUE) and community diversity of fishery resources in Dapeng Bay, China were analyzed based on trawl survey data in spring (March) and summer (May) of 2013 as well as autumn (August) and winter (December) of 2012. Results demonstrated that there are 113 fishery species, which belong to 78 categories, 50 families, 14 catalogues, 3 classes. There are the most species in summer (61 species) and about 56 species in other seasons. In all four seasons, fish and crustacea are dominant species, and there are the fewest cephalopoda. High values of SCPUE occur in spring and autumn, reaching 5.65 and 5.33, respectively. SCPUE is generally low in summer, ranging between 0.52 - 0.96. Fish biodiversity is the highest in summer and the lowest in winter. Among biodiversity, Shannon-Wiener diversity index, Margalef diversity index and Pielou evenness index vary in the same trend. They are decreasing from summer, spring, autumn to winter successively. Therefore, there are violent seasonal variation of species composition, quantity and structure of fishery resources in Dapeng Bay. The community structure and function are highly stable in summer, but they have poor stability in autumn and winter. This research can provide scientific references for protection and sustainable use of fishery resources in typical offshore fisheries area in the SCS.
Quantity, density, distribution and community diversity of fishery resources not only reflect utilization of fishery resources, but also important contents to understand coastal ecological environment. Structure and function of fishery resources are often used as one of health evaluation indexes of marine ecosystem [
Dapeng Bay is a typical fisheries area in the coasts of SCS, with typical representativeness in the offshore area of SCS. Based on trawl survey data in Dapeng Bay from 2012-2013, CPUE was standardized by the generalized linear models (GLM) and seasonal variation on species and community diversity of local fishery resources was analyzed. Seasonal variations of fishery resources in Dapeng Bay are analyzed, aiming to provide scientific references for sustainable utilization and management of fishery resources in the coastal area of SCS.
Dapeng Bay locates in the north of the SCS and the western Shenzhen sea area. There are 0.40 km2 of shallow sea aquiculture area and 2.54 km2 of artificial fish reef area. Net cage and buoyant raft hanging culture are dominant aquiculture ways. It is a typical offshore fisheries area in the SCS (
With reference to the method of Guan [
Lg ( CPUE + c ) = Year + Lon + Lat + Month + SST + Chl-a + error . (1)
where CPUE is the caught mantissa in trawl survey per hour, c is a constant and is determined 10% of total average number, Year is year, Lon is longitude effect, Lat is latitude effect, Month is monthly effect, SST is sea surface temperature,
and Chl-a is Chlorophyll a concentration. error obeys to the normal distribution of N(0, σ2).
Common Kriging interpolation of large-sized and unevenly distributed data has been accepted as the best method and is widely used in many fields. Based on spatial information of Chl-a and SST, the common Kriging method of statistical module in ArcGIS spatial interpolation was adopted for spatial interpolation of environmental survey data in Dapeng Bay in spring (March) and summer (May) of 2013 as well as autumn (August) and winter (December) of 2012 [
In all survey, sample collection and analysis were accomplished according to Specification for Marine Monitoring (GB17378-2007) and Specifications for Oceanographic Survey Marine Biological Survey (GB/T12763.6-2007). Quantity and weight of caught fish species were recorded in site. Species identification and biological test were performed in laboratory. Dominant species were established according to the calculated degree of dominance [
Y = n i N ∗ f i , (2)
D ′ = ( S − 1 ) / ln N , (3)
H ′ = − ∑ i = 1 S P i log 2 P i , (4)
J ′ = H ′ / log 2 S , (5)
where ni is the catch quantity of the ith species, fi is the frequency of occurrence of the ith species, N is total number of biontin samples, S is total species in bottom trawl samples, and Pi is percentage of the ith species in total number of samples.
A total of 113 species were caught in Dapeng Bay in four seasons, which belong to 78 categories, 50 families, 14 catalogues, 3 classes. Most of them are Decapoda, accounting for 35 species (30.97%) of 10 families. Perciformes is the second dominant species, accounting for 33 species (29.20%) of 14 families. Teuthoidea and Octopoda have the least proportions, accounting for 1 species (0.89%) of 1 family, respectively. In all four seasons, there are the most species in summer (61 species) and fewer species in rest three seasons (56 species) (
and seeking foods change greatly in different seasons.
There are 29 dominant species with the dominance Y > 0.02 (
Statistical distribution of CPUE in the research area has to be determined before GLM-based standardization. The CPUE histogram shows skewed normal distribution (
It can be seen from
Fish | Crustaceans | |
---|---|---|
Spring | Parargyropsedita 0.03 | Dorippefacchino 0.36 |
Portunushastatoides 0.09 | ||
Portunussanguinolentus 0.04 | ||
Eucratecrenata 0.03 | ||
Parapenaeopsistenella 0.03 | ||
Summer | Leiognathusbrevirostris 0.08 | Oratosquillaoratoria 0.14 |
Parargyropsedita 0.06 | Metapenaeopsispalmensis 0.97 | |
Lepidotrigla japonica 0.05 | Parthenope validus 0.054 | |
Sauridaundosquamis 0.04 | Dorippefacchino 0.04 | |
Apogonquadrifasciatus 0.04 | ||
Autumn | Siganusoramin 0.07 | Oratosquillaoratoria 0.47 |
Polynemussextarius 0.04 | Arcaniaheptacantha 0.17 | |
Parthenope validus 0.17 | ||
Hemigrapsussanguineus 0.17 | ||
Portunustrituberculatus 0.17 | ||
Charybdis bimaculata 0.17 | ||
solaris 0.17 | ||
Metapenaeopsispalmensis 0.04 | ||
Winter | Polynemussextarius 0.03 | Dorippefacchino 0.61 |
Portunussanguinolentus 0.10 | ||
Portunushastatoides 0.07 |
(5.65) (
SCPUE at S10 is high (3.51) (
Community diversity indexes in Dapeng Bay include Margalefdiversity index, Shannon-Wiener diversity index and Pielou evenness index, which show obvious seasonal variations (
Dapeng Bay possesses abundant fishery resources. There are the most fishery species in summer and relatively fewer in rest three seasons, conforming to the trawl survey of Xu et al. [
Fish is the dominant species in summer in Dapeng Bay. Fish species such asParargyropsedita has big size, long life and slow growth. They pertain to k selective type, but have low degree of dominance. In spring, autumn and winter, degree of dominance of big fish is relatively low. Dominant species include Polynemussextarius, Parachaeturichthyspolynema, etc. Crustaceaoccupies the absolute advantage. Dominant species such as Oratosquillaoratoria and Dorippefacchino have high degree of dominance. These small biological species have short life and quick growth. They belong to the r selective type [
Margalef diversity index, Shannon-Wiener diversity index and Pielou evenness index show basically same seasonal variations. They achieve the highest in summer, followed by spring, autumn and winter successively. The highest community diversity is achieved in summer, indicating that there are the most abundant fishery resources in summer and the community structure in summer is the closest to the ideal state [
SST is one of the most important environmental factors that influence fishery resources. It is one of evaluation indexes of physical changes, including ocean current, water mass, tidal, fishing ground and primary productivity [
Fishery resource distribution based on Chl-a is related with marine food chain mechanism. The abundant phytoplankton resources attract a lot of zooplankter which live on them, thus further enriching fishery resources which live on the zooplankter. In this study, SCPUE is high when Chl-a is low in spring (1.99 mg/m3) and autumn (1.07 mg/m3). This reflects the “low Chl-a and high fishery resources” to some extent [
Dapeng Bay is in the northwest waters of the SCS with low latitude. Characteristics of fishery resource structure are mainly caused by reduction of fishery organism and frequent species replacement caused by excessive catching as well as poor community stability. Therefore, it is necessary to change the traditional exhausting catching pattern and control and reduce catching intensity strictly. It shall reduce catching activities of fishing ships, determine catching intensity and maximum proportion of larva, and use the smallest meshing size [
In this study, seasonal variations of fishery resources in typical offshore fisheries areas in SCS are analyzed based on Dapeng Bay, China. SCPUE of fishery resources in Dapeng Bay is low in summer, indicating that the fishing off policy in summer can protect fishery resources to some extent. The community diversity is higher in summer and low in winter. The energy transfer efficiency between different nutrient levels in Dapeng bay in spring and summer is relatively close, indicating that the ecosystem is relatively table. K selective type is the dominant species in summer and r selective type is the dominant species in autumn. This reflects that catching intensity can influence regional resource structure. The catching intensity in autumn is higher than that in summer, so r selective type will replace the k selective type as the dominant species. Further investigation will be conducted on Dapeng Bay, providing scientific references for protection and sustainable use of fishery resources in typical offshore fisheries area in the SCS.
This work was supported by National Key Technology Support Program (No. 2012BAD18B01, 2012BAD18B02) and the Science and Technology Project of Shenzhen of China (No.JSGG20141015154342147, JCYJ20160331141759795).
Mao, J.M., Yuan, H.R., Yu, J., Chen, P.M. and Hu, Q.W. (2017) GLM-Based Analysis on Seasonal Variation of Fishery Resources in Dapeng Bay, China. Journal of Geoscience and Environment Protection, 5, 32-45. https://doi.org/10.4236/gep.2017.510004