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    • Book chapter

      Diet and sexual maturity of yellowfin and skipjack tuna taken by hand lines from fish-aggregating 'payaw' off northwestern Luzon 

      JR Mamhot & ER Verceles - In TU Bagarinao (Ed.), Research Output of the Fisheries Sector Program, 2007 - Bureau of Agricultural Research, Department of Agriculture
      Skipjack tuna Katsuwonus pelamis and yellowfin or albacore tuna Thunnus albacares taken by hand lines from the 'payaw' off La Union and Ilocos Sur were sampled from April 1994 until August 1995. Skipjack ranged from 28 cm to 59 cm in fork length and from 0.35 to 4.2 kg in weight. Yellowfin ranged 24–67 cm and 0.25–6.4 kg. The common size landed was about 40 cm for both species. Size at first maturity of skipjack was about 41 cm in males and 42 cm in females. The yellowfin tuna taken by hand lines were almost all immature except two mature males about 60 cm long. About 18 prey species were identified in the stomachs of skipjack, and about 25 prey species in yellowfin. The preferred prey were mantis shrimps and squids. Small fishes and other invertebrates were also eaten. Mesopelagic lanternfish were eaten by yellowfin and epipelagic jellyfish were eaten by skipjack.
    • Book chapter

      The tuna fishery off northwestern Luzon: catch of purse seines and hand lines operating around fish-aggregating 'payaw' 

      VV Prado - In TU Bagarinao (Ed.), Research Output of the Fisheries Sector Program, 2007 - Bureau of Agricultural Research, Department of Agriculture
      The tuna fishery along northwestern Luzon was studied from March 1994 to April 1995. About 120 units of fish aggregating ‘payaw’ were set 20–100 km offshore and fished by about 350 handline boats and 6 purse seines. The handline landing areas were in Apatot, San Esteban, Ilocos Sur and in Darigayos Cove, La Union. The resident purse seine was based at Poro Point in San Fernando, La Union; the others were occasional operators. Skipjack tuna Katsuwonus pelamis was the primary species landed by the purse seine and yellowfin tuna Thunnus albacares was mostly landed by the hand lines. These species occurred year-round with peaks during the dry season. The purse seine was operated about 9 sets per month, and landed an average of 51 mt fish monthly (catch rate 5.7 mt/set), highest in November, December and March. Handline fishing was carried out an average of 17 days a month (catch rate about 19 kg/boat-day). The tuna fishery was adversely affected by strong monsoon winds and typhoons. The rough seas inhibit fishing and give the tuna populations much needed respite from the intense fishing pressure.