There are several kinds of tuna. Bluefin, yellowfin, and bigeye tuna are preferred for sushi and sashimi. Yellowfin and bigeye (both also known as ahi), as well as albacore and skipjack (which are often used for canned tuna), are fairly resilient to fishing pressure since they mature quickly and produce lots of eggs. Bluefin tuna, however, grow more slowly and reproduce later in life. Prized as the world’s most valuable sushi fish, bluefin are often caught in numbers that exceed international quotas, depleting stocks across the globe. Since the 1970s, stocks of bluefin in the Atlantic, for instance, have decreased by almost 90-percent. In general, there are concerns over the manner in which most tuna is caught: usually with longlines or purse seine nets that take in a large amount of ‘unwanted’ (and often endangered) marine life as bycatch, even when the nets are ‘dolphin-safe.’ Tuna caught with handlines or trolling, though, create little in the way of bycatch. There are also health risks related to mercury levels in tuna.