Catch performance of coastal squid jigging boats using LED panels in combination with metal halide lamps
Highlights
► Light emitting diode panel (LED) was tested in squid jigging fishery. ► Fishing trials were done with LED and different number of metal halide lamps (MHs). ► Non-linear relationship was observed between number of MHs and catch. ► Combination of LED and MHs will maintain present catchability with less electricity.
Introduction
Squid fishing has attracted interest world-wide over the last two decades due to its commercial potential under the present condition of targeting species lower down the food web (FAO, 2005). Among the various harvesting methods for squid, jigging with artificial lights is considered as a highly selective fishing method (Rathjen, 1991, Tubino et al., 2007). This fishing method is mainly conducted by Japan, China (Chen et al., 2008), South Korea (Choi et al., 2003) and Taiwan (Zhou, 2003) in east Asia. The Japanese squid jigging fisheries target cephalopods, such as Japanese common squid Todarodes pacificus and swordtip squid Photololigo edulis.
The squid jigging fishery operating around Japan consists of two size classes: large boats (more than 20 gross tonnage (GT)) in offshore and coastal waters licensed by the national government, and small boats (less than 20 GT) in coastal waters licensed by local governments. In 2007, these coastal boats of less than 20 GT landed 103,000 tons of cephalopod (approximately 32% of the annual landing of cephalopods in Japan).
Squid jigging fishery typically uses two specialized fishing machines that make operations efficient: one is fishing lights to attract squid and the other is automated squid jigging machines to catch them with less labor. Fishermen generally think that the catch of squid increases with the increase of light power. High power metal halide lamps (MHs) are therefore extensively used in most jigging boats in Japan.
To avoid competition of over-capitalization and consequent excessive fishing capacity of high power fishing lamps among fishermen, efforts have been made to promote the use of the optimum number of fishing lamps and restrictions to limit the output power for fishing lights have been suggested (Arimoto et al., 2003). However, the scientific basis for selecting the type of light source and its power as fishing lights still remains unverified. There are many factors that affect squid attraction such as the quality of light (e.g. wave length), quantity of light (e.g. power), and arrangement of fishing lights. In addition, underwater irradiance level and distribution created by these factors are influenced by the optical characteristics of seawater and influence squid behavior (Arakawa et al., 1998, Shikata et al., 2011). Information about the relationship between fishing lights and squid behavior is still limited and consequently fishermen determine the type, number and power of fishing lights based on their personal experience.
The squid jigging fishery now has set up voluntary regulations for each class of boat and for each fishing ground (e.g. 19 GT boats operating further than 12 miles from the coastline can use a maximum of 160 kW electric power for lighting). Power for fishing lights with such high energy consumption accounts for about half of the operating costs (Demura, 2008).
Low power light emitting diode panels (LEDs) have recently been focused on as a new light source for use as a fish attracting light. LEDs have different characteristics over conventional light sources (e.g. MHs) including emitting light of a specific band of wavelength, narrow beam spread, longer lifetime, and lower energy consumption. In squid jigging fishing trials with only LEDs, catches were less than conventional operations with MHs however fuel consumption was greatly reduced (Fishing Boat and System Engineering Association of Japan, 2009). Consequently, the use of LEDs with a lower number of MHs has been tested so far in the squid jigging fishery in Japan.
In order to confirm catch performance of coastal squid jigging boats using a combination of LEDs and MHs, we carried out fishing trials targeting T. pacificus and P. edulis by using LEDs with different numbers of MHs. We analyzed the catch results in relation to the number of MHs and other relevant factors, through model analysis using generalized linear models (GLMs).
Section snippets
Fishing trials
Fishing trials were conducted with 9 boats (19 GT) belonging to the Katsumoto Fisheries Cooperative in Nagasaki Prefecture. Five boats targeted P. edulis in the southwestern waters of the Sea of Japan around Iki and Tsushima islands and off Shimane Prefecture (hereafter referred to as “Iki”), and 4 boats targeted T. pacificus in the northwestern waters off Hokkaido Prefecture (hereafter referred to as “Hokkaido”) during 1 August–30 September 2009 (Fig. 1).
All boats were equipped with 50 blue
Catches of P. edulis off Iki
A total of 139 operations were conducted on 30 days by 5 boats during 1 August–30 September. There were no operations around the full moon (6 August and 5 September) and most operations were done in waters shallower than 200 m (Fig. 1A). Daily catch of each experimental boat ranged from 0 to 232 boxes (mean 46.2 ± 48.15 SD). During the same period, catches by 20 conventional boats (equipped with only MHs) ranged from 0 to 320 boxes (mean 51.9 ± 45.47 SD). The daily catches by both experimental and
Discussion
In this study, we attempted to describe the influence of LEDs with different numbers of MHs on squid catch, to seek an optimum combination of these light sources for coastal squid jigging boats in Japan. Variances of squid catch by 9 boats with different numbers of MHs were analyzed through addressing significant catch factors (MH, Boat, and Lunar) and a relevant factor to squid abundance (Month) using GLMs. The Model Iki indicated that the catch of P. edulis was influenced not only by the
Acknowledgements
We are deeply grateful to the late Masa-aki Yamakawa, a director of general affair division, Katsumoto Fishermen's Cooperative, Nagasaki, and captains and crews of experimental boats for their cooperation during fishing trials. We appreciate the helpful comments and suggestions by Professor Tadashi Tokai, Tokyo University of Marine Science and Technology on an earlier version of this manuscript. This study was carried out as a part of the energy saving project of Fisheries Agency, Government of
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