Perspectives on the Morphological Elements of Circle Hooks and Their Performance in Pelagic Longline Fisheries

Use of circle hooks is regarded as an effective method to reduce incidental mortality of non-targeted species (e.g., sea turtles) in longline fisheries. Currently, various types of circle hook are produced and distributed commercially. Many researchers worldwide have examined the effect of circle hooks on hooking location, catch rate, and/or mortality for various species, using different types of hooks of various shapes and sizes. However, much work remains to be done to quantify the effects of circle hooks on catch and mortality rates of both target and non-target species. Consideration of practical utility is also important to facilitate wider application of circle hooks in commercial fisheries. Here we focus on some elements of circle hook morphology, i.e., hook width, offset, and incurved point angle, and discuss their potential effects on hook function (i.e., hooking location, catch rate) and practical utility. Further empirical circle hook studies are required to verify the effects discussed here.