Fluctuations of pelagic fish populations and climate shifts in the Far-East regions

Transcription

1 Fluctuations of pelagic fish populations and climate shifts in the Far-East regions - METHOD: - Periods: April, late June-early July and September late June-early July 1995 Yeong Gong, Hee-Dong Jeong, Jong Wha Park, - Environmental Young-Sang Suh, factors: Ki-Tack Seong, Temperature Sang-Woo and Kim, Salinity Kwang-Ho Choi with CTD - Zooplankton: Bongo net (.33 mm mesh) with a oblique towing from ca. 2-m depth to surface National Fisheries Research and Development Institute, Busan , Korea

2 Study Objective To investigate the alternation of dominant species and the regional - METHOD: synchrony in long-term catch trend for seven pelagic fish - Periods: populations April, in the late Tsushima June-early Warm July Current() and September and Kuroshio-Oyashio Current() regions. late June-early July 1995 Data - Environmental and Methods factors: Temperature and Salinity Dominant pattern with CTD exhibiting a peak of abundance and regional - Zooplankton: synchronies Bongo in the net fluctuation (.33 mm mesh) patterns with for a oblique seven fish populations towing are from examined ca. 2-m in relation depth to surface the climate shifts on the basis of historical catch records from the Annual Fisheries Statistical Reports for the FAO area 61 and on the climate indices (e.g. NPI) and upper layer thermal anomalies in the two regions (Minobe, 1997, Minami et al., 1999; NFRDI, ).

3 - METHOD: - Periods: April, late June-early July and September late June-early July Environmental factors: Temperature and Salinity with CTD - Zooplankton: Bongo net (.33 mm mesh) with a oblique towing from ca. 2-m depth to surface Fig. 1-a. Schematic current systems in the East/Japan Sea and its adjacent waters. indicates the East/Japan Sea, East China Sea and Yellow Sea, and indicates the Kuroshio-Oyashio Current regions and the Okhotsk Sea.

4 Catch in 1 3 tonnes Fig. 1- e. Catch of herring in the Far-east region during 191~23. Korea Japan 6 Herring Sardine Anchovy Catch in 1 3 tonnes Fig. 2-e. Catch of sardine in the Far- east region(and ) during 191~23. Korea Japan Catch in 1 3 tonnes Fig. 3-e. Catch of anchovy in the Far-east region(+) during 191~21. Korea Japan Catch in 1 3 tonnes Catch in 1 3 tonnes Jack mackerel Fig. 4-e. Catch of jack mackerel in the and during 1953~23. Squid Fig.7-e(R). Catch of common squid in the Far-east region during 1895~23. Catch in 1 3 tonnes Chub mackerel Fig. 5-e. Catch of Chub mackerel in the Far-east region during 1926~23. PDO shift 5yr( ), 2 yr( ) Taiwan Korea Japan Catch in 1 3 tonnes( Saury Fig. 6- e. Catch of Pacific saury in the Far- east region during 1926~23. Fig. 1. Time series of catches for small pelagic fish populations from the (Yellow Sea-East china sea-east/japan Sea) and (NWPacific-Okhotsk Sea) regions. Environmental index (PDO) is included. Basin scale synchrony Abundance of herring, sardine, jack mackerel, chub mackerel, saury and common squid of the region have been varying substantially in phase with those of the region. Korea Japan

5 Fig. 2. Abundant periods and fishing nature for pelagic fishes in the (Northwest Pacific and Okhotsk Sea) and (Yellow Sea, E. China Sea and East/Japan Sea), Common name - METHOD: (Cont.) Pacific 187- Gill-net, (1897) (1973) (1998) Inhabit subarctic coastal herring 23 Purse seine - Periods: April, late June-early July and September waters and Yellow Sea (Cont.) 191- Purse seine (1937) (1988) Incidental fishing in 23 Setnet = limited area of late June-early July 1995 Purse seine <<(199's) - Environmental 191- factors: Temperature Boat seine and () (1969) (1998) Salinity Changes in community 23 Drag net, Gill-net = << structure in YS, ECS with CTD Setnet () << (Cont.) Jack - Zooplankton: (196) Bongo net (.33 () mm Purse mesh) seine with Inhabit a southern oblique warm 23 << << waters towing from ca. 2-m depth to surface Pacific sardine Japanese anchovy mackerel Chub mackerel Pacific saury Common squid Time Possible (192's) (1958) >> (1968) Abundant period, (peak year), Regional difference in catch (1978) = (1974) >> (1996) < (199) >> (1996) < Main fishing gear Purse seine Stick held-dipnet () Gill-net () Jigging and Trawl (from 199's) Factors leading to different amplitude <(199's) Heavy fishing in >> (Cont.) Inhabit haline waters, abundant in <(199's) Availability, shifted fishing to

6 SST NPI(W-S) NWP NPI(W-S) hpa SST Herring Sardine Anchovy J. mackerel C. mackerel Sauary C. squid 1882~ ~ ~ ~1927 (1913) 1925~ ~ ~ ~ ~ ~ ~ ~ ~ ~1988 = 193~1949 Peak in 1937 Cool and warm regime Cool sardine regimes in the 193 s and 198 s are most notable in both regions and followed by warm regime of four species Alternation During the period of an orderly alternation(replacement) of dominant species has been observed in the Far East. After the collapse of herring fishery(192 s) the alternation was ; sardine(193 s) followed by 4 species(saury, jack mackerel, common squid, anchovy, 195 s- 196 s), herring(late 196 s-early 197 s), chub mackerel(197 s) and again sardine(198 s). Length of abundant period Abundant period of the 5 species have lasted for 1-15 years with long periods(2 years) of anchovy and squid. 1964~1975 (1973) = 1955~1975 (1969) > 1959~ ~1963 (196) (1958) = 195~1972 (1968) = 197~198 (1978) 1973~1979 (1974) 198~1992 (1988) 1997~21 (1998) > 199~24 (1998) > 1989~1998 () > 1993~23 (1996) 1988~23 (199) = 199~23 (1996) Fig. 3. Changes in climate(npi) and ocean(sst), and abuntant periods of pelagic fish in the northwest Pacific and its adjacent regions during 189~25.

7 Basin scale synchrony Abundance of herring, sardine, jack mackerel, chub mackerel, saury and common squid of the region have been varying substantially - METHOD: in phase with those of the region. - Periods: April, late June-early July and September Factors leading regional difference in amplitude of sardine catch late June-early July 1995 Regional difference in sardine catch () in the 198 s is - Environmental factors: Temperature and Salinity due to the limited fishing(south of 38 3 N) and incidental catch with CTD by Korean fishing (purse seine targeting mackerel and file fish) - Zooplankton: Bongo net (.33 mm mesh) with a oblique in the. towing from ca. 2-m depth to surface Synchrony under same climate forcing-single population It is postulated that pacific sardine in two regions fluctuate with synchronous pattern under the same climate forcing and reveal different amplitude due to the different nature of fishing and availability, and hence same large single population to conserve.

8 Regional different catch distribution-evolution Significant differences in catch of anchovy, jack mackerel (<) - METHOD: and Pacific saury () between the two regions - Periods: are attributed April, late to the June-early different distribution July and September. The jack mackerel late and June-early anchovy July evolved 1995 in the southern waters and - Environmental prevailed during factors: the warm Temperature period (Ogawa and and Salinity Nakahara, 1979). No adult with Pacific CTD saury are found in the western East China - Zooplankton: Sea and Yellow Bongo Sea net since (.33 the mm fish mesh) inhabit with high haline a oblique waters(gong towing and Suh, from 24). ca. 2-m depth to surface

9 Squid phase in abundance fluctuation The phase difference in the collapse of common squid between the and regions in the 197 s was attributed to the heavy fishing before the response of the squid to the climate shift in -the METHOD: mid 197 s. - Periods: April, late June-early July and September 8 late 7 June-early July Environmental 6 factors: Temperature and Salinity with 5 CTD - Zooplankton: 4 Bongo net (.33 mm mesh) with a oblique towing 3 from ca. 2-m depth to surface Catch in 1 3 tonnes Fig.1-h. Catch of common squid in the Far-east region during 1895~23.

10 Catch in 1 3 tonnes METHOD: 1 - Periods: April, late June-early July and September Fig.1-h. Catch late of common June-early squid in the July Far-east 1995 region during 1895~23. Squid - Environmental amplitude in factors: abundance Temperature fluctuation and Salinity An amount of common with CTDsquid taken in the region were landed - Zooplankton: at the fishing Bongo ports along net (.33 the Pacific mm mesh) coast ( with a region) oblique which are included towing the from former ca. 2-m region depth in the late to surface 196 s. Significant regional difference in the squid catch in the 195 s- 196 s() is due to the shifts of fishing grounds depending on the changes in distribution in association with current-mediated migration circuits.

11 Conclusion - An orderly alternation of dominant pelagic fish has been observed - METHOD: in the catch records from the Far Eastern regions ( - Periods: + ) during April, the late 2th June-early century July. and September - The alternation late was June-early ; herring(191 s July s), chub mackerel (possibly - Environmental 192 s), sardine(193 s), factors: Temperature four species(pacific and Salinity saury, jack mackerel, with common CTD squid and anchovy, 195 s-196 s), herring(late - Zooplankton: 196 s-early Bongo 197 s), net (.33 chub mm mackerel(197 s) mesh) with a oblique and then sardine(198 s). towing from As sardine ca. 2-m biomass depth decreased to surface in association with the climate shifts(in the late 198 s) catch of the four species increased in the warm regime in the 199 s. The abundant period of each species has lasted for 1-2 years.

12 - The abundance of seven species has synchronous pattern of variability - METHOD: in the and regions, suggesting that they are controlled - Periods: by the April, same late climate June-early forcing, July and and they September reveal different amplitude(catch) due to the varying availability and fishing nature in each region, and late hence June-early single July large 1995 population to conserve in spite - Environmental of their widely distributed factors: Temperature population area. and Salinity with CTD - Zooplankton: Bongo net (.33 mm mesh) with a oblique towing from ca. 2-m depth to surface