An overview of historical changes in the fishing gear and practices of pelagic longliners, with particular reference to Japan’s Pacific fleet

Abstract

We identify changes in pelagic longline fishing gear and practices that need to be accounted for in stock assessments. Pelagic longline fishers have continuously modified their fishing gear and practices to improve fishing power and catchability, which has altered the relationship between catch rates and abundance. Advances in technology resulted in the introduction of many electronic devices to assist in navigation, communication and finding target species. The development of synthetic materials allowed improvements to lines and hooks that increased the probability of hooking target species and landing them. Other changes increased fishing power by improving searching efficiency (e.g., satellite imagery) or the time spent on fishing grounds (e.g., freezers). The number of hooks deployed in daily longlining operations has steadily increased since 1950. However, mean soak time did not change significantly because faster longline retrieval and deployment speeds balanced the increased hook numbers. There has been a shift from having all baits available at dawn, to having more available at dusk and at night. In the 1970s, several longline fleets began to exploit a much greater depth range, resulting in increased catchability for deep-dwelling species (e.g., bigeye tuna, Thunnus obesus) and reduced catchability for epipelagic species like blue marlin (Makaira nigricans). Research has been mostly limited to the effects of longline depth on the catchability of target species. Recent experiments have quantified the effects of bycatch mitigation measures on fishing power and catchability. Progressive improvements in expertise and technological improvements in the gear will also affect fishing power, but are particularly difficult to quantify.

STANDARDIZING CPUE OF ALBACORE TUNA (Thunnus alalunga Bonnaterre, 1788) ON TUNA LONGLINE FISHERY IN EASTERN INDIAN OCEAN

“…Its mean that proporsional change in CPUE is expected to the proporsional change in the stock size (Riswanto, 2012;Chen & Chiu, 2009;Bordalo-Machado, 2006;Maunder & Punt, 2004;Ortega-Garcia et al, 2003). The abundance index of fish is mostly based on CPUE index especially on industrial tuna longline fishery (Maunder & Punt, 2004;Maunder et al, 2006a;Maunder et al, 2006b;Ward & Hindmarsh, 2007). The abundance index based on nominal CPUE on tuna longline fleets did not taken into account confounding factors such as fishing strategy and water environment condition, which can separate indication of abundance based on hook rate (Bach et al, 2000;Hampton et al, 1998).…”

Changes in Fishing Pattern From Surface to Deep Longline Fishing by the Indonesian Vessels Operating in the Indian Ocean

“…Longline gear was arbitrarily classified based on the number of branch lines or hooks between floats (Suzuki et al, 1977;Marcille et al, 1984;Lee & Nishida, 2002;Lee et al, 2005), as the latter is considered an index of the maximum fishing depth (Bach et al, 2000;Ward & Hindmarsh, 2007). Note that the number of branch lines and hooks between floats are used interchangeably.…”

Factors that determine the quality of bigeye tuna, caught in the western tropical Atlantic Ocean

“…To assess the quality, quick methods are needed. Sensory evaluation is used for most fish because of the speed, reliability and ease, and this evaluation uses only the human organs of sense to generate accurate and direct information about the quality attributes (Veciana-Nogue´s et al, 1997;Warm et al, 2001;Pons-CascadaSa´nchez et al, 2006;Pe'rez Elortondo et al, 2007). Hackney and Garrett (1985) reported that the quality of fish is influenced by the environment and fishing practices.…”

“…Ward and Hindmarsh (2007) mentioned that the fishing gear and practices are continuously modified to achieve improvements in size, quality and quantity of the target species.…”