Fishing the marine food web along the Indian coast

E. Vivekanandan*, M. Srinath, Somy Kuriakose

Fisheries Research 74 (2005) 223–231

印度沿岸水域因漁業捕撈影響食物網變動情形

報告者 :何珈欣

Outline

Introduction

Objectives

Material & Method

Result

Discussion and conclusions

Introduction

INDIA NE COAST

SE COASTSW COAST

NW COAST

BAY OF BENGAL

ARABIAN SEA

Indian

Objectives

Pauly et al. (1998) called “fishing down marine food webs”.

Along the Indian coast, there has been an unprecedented expansion of fishing fleets in the last half century in the present paper, the trend in fishing the marine food web along the Indian coast during 1950–2002 has been analysed.

Material & Method

Mean trophic level(MTL)

Fishing-in-balance index(FIB)

Trophic category

Statistics of Indian coast catch

MTL :The mean trophic level of landing in year j

Yij :The landing of species i in year j

TLi :the trophic level of species i

Mean trophic level(MTL)

ij

ijij

Y

YTLMTL

Material & Method-1

4

3

2

Top predator

Herbivores Omnivores

Mid-level carnivores

Material & Method-1

Trophic levels

Yi :Landing at year i

TE:trophic efficiency (here set at0.10)

Y0 and TL0 are the landing and mean TL of the first year of the series

Fishing-in-balance index(FIB)

TLoTLi

TE

1O

TE

1i Ylog-YlogFIB

Material & Method-2

Material & Method-2

110

100

1000-0. 3-0. 2-0. 1

00. 10. 20. 30. 40. 50. 6

1950 1957 1964 1971 1978 1985 1992 1999Year

FIB

inde

x

FI B i ndex

FiB=0

Trophic levels

FiB=(+)

110

100

1000

Material & Method-2

Trophic levels

110

1001000

FiB=(-)Material & Method-2

Trophic levels

Trophic category

Trophic category 1 (TrC1) herbivores, detritivores and omnivores (TL:2.00–3.00)

Trophic category 2 (TrC2) mid-level carnivores (TL: 3.01–3.50)

Trophic category 3 (TrC3) high-level carnivores and top predators (TL: >3.51)

Material & Method-3

Trophic category 1 (TrC1) Material & Method-3

Vivekanandan et al., in press

Trophic category 2 (TrC2)

Mid-level carnivores (TL: 3.01–3.50)

Material & Method-3

Mid-level carnivores (TL: 3.01–3.50)

Material & Method-3Trophic category 3 (TrC3)

Result

NW

SW

SE

NE

Result

Period NW SW NE SE TrL FiB TrC TrL FiB TrC TrL FiB TrC TrL FiB TrC

1953-1962 3.27 0.48 TrC3 3.12 -0.22 TrC2 3.32 -0.18 TrC2 3.52 0.03 TrC21963-1972 3.33 0.49 TrC3 2.94 -0.16 TrC1 3.28 0.13 TrC2 3.51 0.19 TrC21973-1982 3.34 0.76 TrC3 3.09 0.06 TrC2 3.27 0.52 TrC2 3.48 0.36 TrC21983-1992 3.38 0.96 TrC3 3.21 0.33 TrC2 3.33 0.87 TrC2 3.43 0.41 TrC21993-2002 3.38 1.13 TrC3 3.28 0.46 TrC2 3.22 0.99 TRC2 3.32 0.45 TRC2

Mean 3.32 0.72 3.14 0.09 3.29 0.43 3.45 0.27CV 2.8 43.1 5.4 312.7 2.6 113.4 2.3 66

Table 1Decadal changes in mean TrL and FIB and TrC values

TrC2 TrC2

Result Southwest coast (SW)

Trends in parameters related to fishing the food web along the southwest coast

Trends in parameters related to fishing the food web along the southeast coast

Southeast coast (SE)

Result

1980

Indian coast

Trends in parameters related to fishing the food web along the Indian coast

Discussion

1.The Environment condition

2.Advancement of fishing technologies

Table2.Corrleation analysis of TrL and FIB with total catch and catch of each TrC

Corrleation analysis of TrL and FIB with total catch and catch of each TrC

Discussion-1

The Environment condition

The surface chlorophyll and the biomass of benthic organisms in the Arabian Sea is very high compared to the Bay of Bengal in the east coast .

Whereas upwelling enhances the productivity and abundance of planktivores along the SW and abundance of demersals along the NW coast. Along the SW the fishery is driven by upwelling and other environmental variabilities, and rarely shows stability.

Table1.Fisheries profile of four coastal zones in the Indian mainland

Advancement of fishing technologiesDiscussion-

2

Discussion-2

Advancement of fishing technologies

Fishing the food web could be influenced by the impacts of advancement of fishing technologies.

The trawlers progresses continuously during the 1960~2000.

Thank You