Megrim

Overview

The Megrim (Lepidorhombus whiffiagonis), also known as the Megrim Sole or Whiff, is a commercially valuable deep-water flatfish belonging to the family Scophthalmidae. Inhabiting the deeper continental shelf and upper slope waters of the Northeast Atlantic Ocean, this sinistral (left-eyed) flatfish is an active, predatory hunter. Unlike many shallow-water flounders that bury themselves in sand and wait for prey, the megrim is an athletic, semi-pelagic swimmer with a cavernous, toothy mouth, frequently swimming well above the muddy seabed to pursue small schooling fishes and deep-water squids.

Biology and Physical Characteristics

Lepidorhombus whiffiagonis is a sinistral flatfish, meaning both of its large, close-set eyes migrate to the left side of the body during larval metamorphosis. The body is remarkably thin, slender, and almost translucent, covered in fragile, deciduous ctenoid scales that rub off easily when handled. The eyeless (right) side is a pale, milky-white, while the eyed (left) side is a drab, sandy yellowish-brown, often marked with faint darker clouds or spots for camouflage on deep muddy bottoms. The head is large, terminating in an exceptionally wide, cavernous mouth armed with sharp, needle-like teeth and a prominent, undershot lower jaw engineered for seizing active prey.

Behavior and Ecology

Megrims inhabit cool, dimly lit waters along the outer continental shelf break. While they rest on soft muddy sediments during periods of inactivity, they are highly capable swimmers that exhibit benthopelagic hunting behavior, ascending several meters into the water column to ambush small fishes like whiting, Norway pouting, and sprats. Spawning occurs in deep water between January and May along the continental shelf edge southwest of the British Isles and in the Bay of Biscay. The eggs and larvae are pelagic, floating in surface currents until the juvenile undergoes asymmetry metamorphosis and settles onto the seabed.

Conservation and Human Impact

Assessed as Least Concern by the IUCN, the Megrim supports significant commercial fisheries across the Northeast Atlantic, particularly for Spanish, French, and British demersal trawlers. European Union fisheries management maintains strict Total Allowable Catches (TACs) and minimum landing sizes for megrim stocks in the Celtic Sea and Bay of Biscay. Because current fishing mortality is within sustainable maximum sustainable yield (MSY) biological limits, populations remain healthy and resilient.

Interesting Factoid

The Megrim has such delicate, semi-translucent skin and scales that when held up to a light source, its internal spine and bony rib structure can be seen clearly through its body.