Status of fisheries of billfish in Pakistan with special reference to swordfish (Xiphias gladius)

Billfish form important part of the catches of tuna and tuna like fishes from Pakistan. Its landings during 2019 were reported to be about 4,431 m. tons which is about 25.34 % less than 2018. The decrease is attributed to a much longer closed season observed by the tuna gillnet fisheries in 2018. Fishing in 2019 was stopped in the late March and initiated only in last week of August i.e. almost no fishing for five months as against normal 2 month ban of June and July. Environmental conditions including high sea surface temperature during August to October and appearance of jellyfish  bloom during October and December has also affected the catches of billfishes in Pakistan.

Government of Pakistan was provided species-wise data of billfishes to IOTC since 2018 which indicated that out of six species of billfishes Indo-Pacific sailfish (Istiophorus platypterus) contributed about 2,234 m. tons,  black marlin (Istiompax indica) 978 m. tons, striped marlin (Kajikia audax) 865 m. tons whereas  Indo-Pacific blue marlin (Makaira mazara) contributed only 374 m. tons. Contribution of shortbill spearfish (Tetrapturus angustirostris) and swordfish (Xiphias gladius)  was insignificant. Billfishes were found in commercial quantities throughout the year however, period between November through May is the peak season of their catches. Billfishes are not locally consumed but transported to neighboring country through land or sea route.

The study further revealed that due to introduction of subsurface gillnetting the catches of billfishes is substantially reduced. Billfishes are known to inhabit surface water and when gillnet is placed 2 meters below the surface, the catches of billfish are reduced. It was observed that on average about 37 % reduction in catches of billfish is observed in subsurface gillnetting.

Swordfish (Xiphias gladius) was observed to be one of the rarest billfish being caught by tuna gillnetters in Pakistan. It is interesting that almost all swordfish being caught are juveniles and seldom any adult are caught by tuna vessels.