While concerned consumers fret over which fish are correct to order at their favorite seafood restaurant, heading to websites maintained by groups such as the Environmental Defense Fund for guidance on the “eco-best” and “eco-worst” fish to purchase, the truth about commercial fishing in the United States is that a regulatory framework designed to limit overfishing results in vast numbers of fish per year being scooped up on boats and dumped right back off, dead, never consumed by any ­human. Concerned about “endangered” bluefin tuna? Tell it to the tuna long-liners who’ve had to cut loose untold numbers of dead bluefins in recent years, owing to the restrictions that come with winding up on the endangered-species list.