IMPACT OF CLIMATE ANOMALY ON CATCH COMPOSITION OF NERITIC TUNA IN SUNDA STRAIT

Tongkol komo/kawakawa (Euthynnus affinis) and tenggiri (Scomberomerus guttatus) are commonly caught by mini purseiners operated in Sunda Straits and landed in Labuan, West Java. This species inhabits coastal water and has preference staying in relatively warm water. Oceanography parameters commonly influencing the distribution of Euthynnus affinis are temperature, current, and salinity. The oceanography of Sunda Strait is influenced by water masses coming from the north that mainly originated from the Java Sea and water masses from the south mainly originated from Indian Ocean. The internal oceanography of Sunda Strait is also influenced by upwelling and monsoon as regional climate anomaly (ENSO and Indian Ocean Dipole Mode). This paper describes the influence of Dipole Mode (positive and negative event) and ENSO (ElNino/La-Nina) to the catch dynamics of neritic tuna particularly in Sunda Straits waters. The results shown that regional climate anomaly influenced neritic tuna catch and its composition. The catches Euthynnus affinis in phase negative dipole mode or La-Nina were higher and dominated the catch composition of pelagic fishes of Sunda Strait. Similar situation also is showen by Scomberomorus commerson.

Indian Ocean Tuna Commision/IOTC (2006) reported that Euthynnus affinis, inhabits coastal water and has preference staying in relatively warm water 18°-29°C.This species forms school that appears down to 400 m depth.Oceanography parameters commonly influencing the distribution of Euthynnus affinis are temperature, current, and salinity (Hela & Laevastu, 1970).Gunarso (1985) also reported, Euthynnus affinis is susceptible to temperature and salinity from 0.03 0 C and 0.02 ‰ espectively.
Labuan fishers operate two kinds of fishing gears namely mini purse seiners and danish seine (payang) both are operating on daily basis.The mini purse seiner is for night fishing while danish seine is day the fishing.
Both fleets have relatively similar fishing ground and the area spreads from Banten coast to the south within the depth of 200 m depending to the seasons (Muripto, 2000).
Current information is limited to enable to adresses the influence of regional climate anomaly on fisheries resource specifally for the neritic tuna in Indonesian water.This paper describes the influence of Dipole Mode (positive and negative event) and ENSO (El-Nino/La-Nina) on the cacth dynamics of neritic tuna particularly in Sunda Straits for the periode of 1994 to 2009.

MATERIALS AND METHODS
Research was conducted in Sunda Strait Eastern part of Indian Ocean, geographically is located whithin 102.5 0 -108.00 E and 4.5 0 -7.5 0 S (Figure 1).
Regional climate anomaly that influence internal condition of Sunda Strait oceanography is El-Nino/ La-Nina (ENSO) and Indian Ocean Dipole Mode/IOD (Samsudin et al, 2003).El-Nino/La-Nina events from 1994 to 2010 are showing in the following map (Figure 2) and Table 1.et al., 2000).Descriptive analysis is conducted to compare the catch pattern of Euthynnus affinis and Scoromberomorus guttatus particularly on years that climate anomaly occurs.

Oceanography Pattern of Sunda Strait
The oceanography of Sunda Strait is influenced by at least two water masses i.e: the water masses comes from the north that mainly originated from the Java Sea and water masses from the south mainly originated from the Indian Ocean.Water masses from the Java Sea have lower salinity and high temperature which influenced by rivers arrounds Java Sea while these from the Indian Ocean were more oceanic with high salinity and low temperature.The two water masses mixed in the central of the straits and its position depends on the strenght of the current of each water masses.The current from southern strait i.e South Java Current (Arus Pantai Selatan Jawa/APJ), South Equator Current (Arus Khatulistiwa Selatan (AKS)) and Monsoon Current (arus Musim (AM)), while the current from northern strait is dominated by Armondo (Arus Musim Indonesia).One in a while oceanography of Sunda Strait is also influenced by upwelling (Muripto et al. 2000;Hendiarti et al 2003) and monsoon as regional cimate anomaly (Samsudin, et al. 2003).In the contrary, during negative dipole mode and/ or La-Nina, upwelling did not occur and commonly the water masses have higher SPL disribution than during normal condition.This condition was recorded and occured in year of 1995 (weak La-Nina); 1996 (negative strong IOD); 1998 (negative moderate IOD in-phase moderate La-Nina); 1999 (weak La-Nina); 2000 (La-Nina lemah); 2005 (weak La-Nina); and 2010 (strong La-Nina) (Figure 3).2001 was a normal year and no influence from IOD and/or ENSO on the Sunda Strait water (Figure 4).Impact of Climate Anomaly on Catch Composition…..in Sunda Strait (Amri, K & F. Satria) The SST distribution from each period from 1994-2012 is presented in Table 2 and its fluctuation is also shown in the graph (Figure 5).The lowest average of SPL distribution occured in the phase of strong positive IOD inphase with El-Nino year of 1994, 1997, and 2006 with respective temperature of 27.97 0 C (inphase with moderate El-Nino), 28.47 0 C (in-phase with strong El-Nino) and 28,77 0 C (in-phase with weak El-Nino).The higher average of SST distribution occured during negative IOD or La-Nina phase with temperature range of 30.49-31.29 0 C. The highest SST occur and found in the phase of strong negative IOD 1996 (31.02 0 C) and moderate negative IOD inphase with moderate La-Nina 1998 (31.29 0 C).The average of SST distribution in the normal phase (2001) was 30.14 0 C.

Sea Surface Chlorophyll
Chlorophyll-a distribution in the period of IOD positive or El-Nino higher than in the period of negative IOD and La-Nina or in normal phase.High distribution of chlorophyll-a in the period of positive dipole mode and El-Nino was due to the occurrence of intensive upwelling during that time.The average of SST and chlorophyll-a distribution from 1997-2009 is presented in Figure 6.1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 Average of SST and Chlorophyll-a Chlorophyll-a SST Looking at the monthly distribution and fluctuation of chlorophyll-a when climate anomaly occurred (Figure 7), revealed that in the period of strong positive dipole mode 1997 and 2006 the distribution of chlorophyll-a was very high, on the other hand during negative phase of dipole mode and La-Nina the distribution of chlorophyll-a was very low.

DISCUSSION
Annual catch of small pelagic and neritic tuna from Labuan during 1993-2008 is presented in (Figure 8).The catch of small pelagic was very high in 1994 (strong phase positive IOD inphase moderate El-Nino) as well as intensive upwelling (low SST and high cholophyll-a) and lower in the period of negative dipole mode and La-Nina (high SST and low cholophyll-a).Different pattern showed by the catches of neritic tuna where high catch in the period of negative IOD and La-Nina (high SST and low cholophyll-a) and lower in the period of positive IOD and El-Nino (low SST and high cholophyll-a).
Figure 9 presents the highest catch of Euthynnus affinis occur in in the period of strong negative IOD associated with moderate La-Nina (1998), followed by the normal period ( 2001) and moderate La-Nina period (1999).Monthly catches fluctuation showed diferent pattern of inter phase.1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 Thousands Annual total catch of pelagic fish species in Sunda Strait 1993Strait -2008 Euthynnus affinis Scomberomorus sp Small pelagic The highest catch of Scoromberomorus spp also occur in strong negative IOD period of 1996 and 1998, but low in the period of positive dipole mode/El-Nino (Figure 10 and Figure 11).There was a similar trend of monthly catches in 1996 and 1998 but with different intensity whithin each month.(1999) (moderate La-Nina) (Figure 13).In the normal phase the proportion of tongkol (Euthynnus affinis) was 16% (2001) (Figure 14).Impact

Figure 1 .
Figure 1.Research area located in Sunda strait.
Climate anomaly occured in 1994 (Positive strong IOD in-phase moderate El-Nino); 1997 (Positive strong IOD in-phase strong El-Nino); and 2006 ( Positive strong IOD inphase weak El-Nino) there was water mass from upwelling in the middle and southern strait with high intensity.In this phase the temperature of water mass become much lower compare to its normal condition.The upwelling water mass with moderate intensity also occured in 2002 (moderate El-Nino); 2003 (weak postive IOD); 2004 (weak El-Nino); 2009 (moderate El-Nino); as well as 2011 and 2012 (weak El-Nino) (Figure 2).
Figure 10: Annual total catch of Scomberomorus comerson in Labuan assosiated with climate anomally.

Figure 12 :
Figure 12: Catch composition of neritic tuna caught by mini purse seine in Labuan during positive Dipole Mode and El-Nino event 1994 and 1997.

Figure 13 :
Figure 13: Catch composition of neritic tuna caught by mini purse seine in Labuan during negative Dipole Mode and La-Nina event 1998 and 1999.

Figure 14 :
Figure 14: Catch composition of neritic tuna caught by mini purse seine in Labuan on Normal 2001

Table 1 .
Event of Dipole Mode and its association with ENSO (El-Nino/La-Nina)

Table 2 .
SST range and average value by phenomenon of regional climate anomaly.