Vendace

Vendace need a specific kind of lake, and the loss of that specificity is the whole reason the British populations have gone.

THE REQUIREMENT IS A DEEP, COLD, LOW-NUTRIENT LAKE. Vendace are pelagic — fish of the open water column rather than of margins or bottom — and they need a body of water large enough and deep enough to hold cool, well-oxygenated water through summer. In the Nordic countries and the Baltic states that describes an enormous number of lakes; in Britain it describes very few.

THEY FEED IN OPEN WATER AND MOVE VERTICALLY WITH THE LIGHT, holding deep in daylight and rising towards the surface at dusk as the zooplankton they eat do the same. So their depth is a function of light rather than of season, and they are caught in the middle of a lake rather than along its edge.

SPAWNING PUTS THEM ONTO CLEAN GRAVEL IN SHALLOW WATER in late autumn or early winter, and the eggs then lie in that gravel through the coldest months. That single requirement is the vulnerability: it needs gravel that stays clean and oxygenated all winter.

WHICH IS EXACTLY WHAT ENRICHMENT AND SILTATION TAKE AWAY. Nutrient enrichment produces algal growth whose decay strips oxygen from deep water in summer and from the lake bed generally; fine sediment from a catchment fills the spawning gravel. Both mechanisms attack a different part of the life cycle and both have operated on the British lakes that held vendace.

INTRODUCED FISH ARE THE THIRD PRESSURE. Species moved into these lakes — often as discarded livebait — compete with vendace and eat their eggs, and the effect on a small isolated population is severe. It is one of the clearest illustrations available of why live fish must never be moved between waters.

AND THE RESULT IS THAT BRITAIN'S VENDACE ARE DOWN TO A HANDFUL OF SITES, with refuge populations established elsewhere as insurance against losing the last of them.

Vendace size is a case where a single number would mislead, and the reason is worth understanding because it applies across the whole coregonid group.

MOST VENDACE ARE 10 TO 25 CENTIMETRES AND 20 TO 150 GRAMS. In the commercial Finnish and Swedish fisheries the fish are small, taken in quantity, and eaten whole — muikku is a small fish by design rather than by accident.

OVER 30 CENTIMETRES AND 300 GRAMS IS LARGE, and reported maxima for the species approach 46 centimetres in some populations.

BUT GROWTH VARIES ENORMOUSLY BETWEEN LAKES, and this is the point. In a dense population competing for limited zooplankton, vendace mature small, breed early and stay small — a stunted population where a 12-centimetre fish is an adult. In a lake with fewer fish and more food, the same species reaches two or three times that. A size figure from one lake is close to useless in another, and citing a maximum without saying which population produced it is how a number becomes misinformation.

THEY ARE SHORT-LIVED, typically maturing at one to two years and rarely exceeding six.

THAT SHORT LIFE MAKES POPULATIONS VOLATILE. A vendace stock is dominated by one or two year classes at any time, and Nordic commercial catches swing accordingly from year to year. It also means a population can recover quickly given the right conditions — and can be lost quickly when a single cohort fails and there is no older reservoir of fish to carry it.

The vendace calendar is upside down relative to most European freshwater fish, and that inversion explains both the fishery and the fragility.

THEY SPAWN IN LATE AUTUMN AND EARLY WINTER, gathering over clean gravel and stony shallows as the lake cools. Eggs are scattered rather than buried and then develop slowly through the cold months, hatching in spring as the zooplankton the fry need begins to appear. The timing is precisely matched to the food supply and is not adjustable.

THE SPAWNING GATHERING IS WHEN THE FISH ARE CONCENTRATED, and it is when the Nordic commercial fisheries take them — including the roe fishery that produces Kalix löjrom, which holds a protected designation of origin and is one of the few European freshwater products with that status. That concentration is also what makes a spawning population easy to over-harvest and easy to lose.

THROUGH SUMMER THEY ARE DEEP AND OFFSHORE, holding in the cool layer below the thermocline and feeding on zooplankton in open water. This is when they are least accessible and least conspicuous.

AUTUMN MIXING BRINGS THEM UP as the lake turns over and the temperature stratification collapses, which is the period when they become catchable to anglers and to nets.

WINTER ICE FISHING TAKES THEM in the Nordic countries on very small jigs at a located depth, which is the same problem as summer — finding the layer the fish are in — solved through a hole rather than from a boat.

AND IN BRITAIN NONE OF THIS APPLIES, because the fish are protected and must not be targeted at all. The British interest in a vendace's year is what its spawning requirement tells you about the state of the lake bed.

Vendace present a handling problem that most anglers never meet, because the damage is done before the fish reaches the surface and nothing at the surface undoes it.

THE FISH LIVES IN OPEN WATER AT DEPTH. It is a pelagic zooplankton feeder of the cool middle and deeper layers of a large lake, and that is where it is hooked. Bringing it up quickly through a substantial pressure change expands the gas in its swim bladder faster than the fish can adjust, and the resulting barotrauma is not something careful handling at the surface can address.

WHICH IS WHY THE RELEASE DECISION IS EFFECTIVELY MADE BEFORE THE FISH IS HOOKED. If the fishing is being done deep, the fish that come up will not go back successfully, whatever the intention. That is an argument about where and how to fish rather than about how to hold a fish.

THE SECOND PROBLEM IS THAT THE ANIMAL IS SMALL AND SOFT. Delicate, soft-scaled, and easily damaged by hands, nets and air. Everything that applies to a small silver fish applies here in a stronger form.

AND THE THIRD IS THE ONE THAT SHOULD COME FIRST IN BRITAIN. In these islands vendace is among the rarest native freshwater fishes, reduced to a very small number of northern lakes, having been lost from most of its former sites. Where it is protected it must not be targeted at all, and the correct response to an incidental capture is to return it in the water without lifting it and to stop fishing in a way that produces more.

THE CONTRAST WITH THE NORTHERN RANGE IS WORTH KEEPING IN VIEW. In Finland and Sweden the same species is abundant enough to support a commercial fishery and is an everyday food fish. Both facts are true, they are facts about populations rather than about the species, and an angler's obligations follow the population they are standing beside rather than the global assessment.

WHAT ACTUALLY HELPS, where any handling is permitted at all: wet hands, no lifting, no net if it can be avoided, and a decision about depth made before the first cast rather than after the first fish.