Perhaps the most colourful family member, the splendid toadfish is easily heard by night diving Scuba divers at Cozumel, Mexico. photo by Andy Lamb

Our Salish Sea representative is erroneously known as the singing (or roaring) bullhead. This plainfin midshipman (Porichthys notatus) is a typical toadfish in design and habitat. It grows to a length of 38 cm (15 in) and lives along the west coast, from central British Columbia, Canada, to southern Baja California, Mexico.

On the edge of the Salish Sea, a group from McMaster University (Ontario, Canada) — the Aquatic Behavioural Ecology Laboratory — has set up shop at the Pacific Biological Station in Nanaimo, B. C. Each spring and summer they study the plainfin midshipman at field sites in the Salish Sea under the leadership of Dr. Sigal Balshine.

As a diver, beach comber, and Vancouver Aquarium collector, I have interacted with it for many years. And for the last 17 years, I lived on a Thetis Island beachfront blessed with excellent plainfin midshipman habitat.

For most the year, the plainfin midshipman lives in the subtidal zone and rests in, on, or slightly above, soft muddy substrates where Scuba divers may encounter it. Awaiting prey, this fish commonly buries with only its eyes and upturned mouth in view. At other times, it will float motionlessly with the aid of its air-filled swim bladder: perfect buoyancy control — as we divers would say.

Of no direct commercial importance, the plainfin midshipman is nonetheless commonly swept up as bycatch by trawlers — particularly in fine mesh shrimp gear. When discarded, individuals float at the surface as a result of over inflated swim bladders. Eager gulls swarm about gorging on these helpless castoffs.

In late April/early May, adult plainfin midshipman journey shallower and into the intertidal zone. This is a dangerous gauntlet. Here at Clam Bay, the harbour seal, river otter, mink, racoon, bald eagle, turkey vulture, osprey, great blue heron, common loon, common raven, northwestern crow, common merganser, and double-crested cormorant all partake of the feast. Likely this but a partial list.

Survivors seek out slab rocks on intertidal sand gullies or the deep crevices in adjacent folded sandstone as safe havens to establish nest sites. Excavation to provide space under the slabs is often required. Once the nesting site is established, males produce sound to warn off competitors and attract females. Recent discoveries show two different male types that produce noticeably different sounds. Successful guardians may have several female visitors — each of which leaves after egg deposition duties are completed. Upon turning a rock, a beach comber can often detect colour (shades of yellow and orange) differences in such egg clutches.

Recently, the McMaster group has documented that “sneaker” males may insert themselves into the action and even fertilize eggs. Upon clandestine departures, the dominant male remains to guard the developing brood. Nature is not fair.

A pair of males tussling over a nest site. Note one on left has survived an attack, likely by a great blue heron. photo by Chelsea Cameron

During late spring and summer, the fertilized eggs develop, and the embryos become evermore visible. This usually culminates in late August and early September at Clam Bay. In a final act, the miniature versions wriggle vigorously, snapping their remaining connections to the rocky nest. Welcome to the real world.

Overturned rock with tiny juvenile plainfin midshipman wriggling away. photo by Neil McDaniel

Adult emaciated male plainfin midshipman now attempt to reverse course and follow departed females into their deeper over-wintering haunts. But again, they face the gauntlet with less mobile, underwater predators such as crabs and sea stars even exacting a toll. Only a relative few will be repeat spawners — but there is a chance.

Newborn plainfin midshipman seek shelter in the shallows and take cover among seaweeds. It appears they may remain there for a year, as Scuba observations during late summer also feature larger yearlings. But at some point, these will make their way deeper, join the adult population, and eventually undertake their own reproductive cycles.

From this vantage point, the migratory life history of the plainfin midshipman is just as compelling as those of the highly publicized Pacific salmon species. In addition, its life cycle is much noisier than that of the more iconic distant relatives.

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