中層拖網漁業之漁具漁法研究－大型網具之試驗－

Studies on Fishing Gear and Methods of Mid-Water Trawling-In the Case of Large Type Gear-

周耀烋(Yau-Shou Chow) ； 高慶和(Ching-Ho Kao) ； 何權浤(Chuan-Hung Ho)

《臺灣水產學會刊》 5卷1期 (1976/12) Pp. 85-93

https://doi.org/10.29822/JFST.197612.0011

摘要

1．在2.5~3.0Kts曳行速度之範圍內，網板的沉降速度，約為延伸曳綱長度之25~30%。亦卽為達某漁撈水深，所需延伸之曳綱長度約為漁撈水深的3~4倍。在低速曳行之倍數較小，高速較大。又曳綱較短時之倍數大，長則較小。
2．曳行速度在2.5Kts以上，曳綱長度在250 m以內，曳綱之形狀得以直線狀視之，若曳綱之傾角量測精確，網具之曳行深度，採用計算法求之簡易且實用。
3．曳行中之網板中心位置，與網口的垂直展開中心線，大約相等一致。
4．網具之操作，因順風、逆風之海況不同，網具沉降深度差異約為10%，前者之網具深度較後者為小。
5．沉降力之增加，對網口之展開及網具之沉降效果有顯著的助益。
6．在2.5~3.0Kts範圍內，曳行中之網口高度約為18 m，確認網具規模之倍增，對網口之實際展開亦有近似倍增之效果。
7．網具兩袖端之水平展開距，估計約為網板展開距之35%，網口水平之展開並未與曳綱長度成比例而增，推測曳行中之曳綱在平面之投影形狀，呈內側彎曲狀所致。

並列摘要

For the study of mid-water trawling, a series of experiments under different conditions was carried out in the Taiwan Strait and the East China Sea adjacent to Northern Taiwan. The results are summerized as follows:
The ratio of the working depth to warp length at towing speeds ranging from 2.5 to 3.0Kts about 1/3 to 1/4. However, it varies with the sea conditions and the weights attached to the net.
The position of the otter board during towing is always kept in the range of vertical extension of the net.
The height of the net mouth is around 17.5 to 18.5m at 2.5 to 3.0Kts on towing speed. Experience indicates that the increase of vertical extension of the net is proportional to the increase of the scale of net mouth.
The change of weights attached to the lower part of the net has a great effect on both the working depth and net height.