The Fish That Converts Feed Better Than Any Land Animal

The Number That Explains the Industry

The feed conversion ratio measures kilograms of feed required per kilogram of weight gain. It is the central efficiency metric in animal protein production.

The biological reasons are straightforward. Fish are cold blooded and spend no energy maintaining body temperature. Water supports their weight, so they spend little on skeletal structure or on standing. And a larger share of the animal is edible.

Feed is the dominant cost in aquaculture, typically around half of production cost, so a conversion ratio a third of beef translates directly into an enormous cost advantage per kilogram of protein.

What Actually Constrains It

If feed efficiency were the binding constraint, salmon farming would have expanded without limit. It has not, and the constraints are biological and regulatory rather than economic.

Sea lice are parasites that attach to farmed salmon, spread readily in dense populations, and harm both farmed fish and wild populations nearby. Treatment is expensive, involves chemical, mechanical, or biological methods, and resistance has developed to several treatments. Lice management is among the largest operating costs and the primary regulatory constraint on stocking density.

Disease outbreaks can destroy a substantial share of a site biomass with little warning, and the losses are not fully insurable.

Licensing limits the number of sites and the biomass permitted at each. Suitable sites require specific water temperature, depth, current, and shelter, and the geography meeting those conditions is limited to a small number of regions.

That combination means supply growth has been slow and largely independent of price, which is why salmon prices have risen substantially over long periods despite demand being met.

The Biological Cycle Determines the Financials

Production has a long and inflexible cycle. Smolt are produced in freshwater, transferred to seawater, and grown for roughly a year and a half to two years before harvest.

That means a decision about how much to stock today produces harvest volume two years later, with no ability to accelerate.

The consequence is a supply curve that cannot respond to price in the short run at all, which is the same structure as the cattle cycle applied to a shorter horizon.

It also produces a distinctive balance sheet. Biological assets, meaning fish in the water, are carried at fair value under accounting standards for agriculture, with changes running through profit. That means reported earnings move with fish prices even before any harvest occurs, and a company can report a large loss from a price decline on stock it has not sold.

The Feed Question

The favourable conversion ratio has a complication in what the feed contains.

Salmon are carnivorous, and feed historically contained substantial fishmeal and fish oil derived from wild caught forage fish. That raises an obvious question about whether the efficiency is real if it consumes wild fish to produce farmed ones.

The industry response has been substantial substitution toward plant proteins and oils, reducing marine ingredient inclusion considerably over two decades. That has largely resolved the wild fish input ratio concern and introduced a new one, since the omega three content of the final product depends on the marine oil in the feed and declines as it is substituted.

Alternative sources including algal oil and insect protein are being commercialised, and cost remains the constraint.

The Land Based Alternative

Recirculating aquaculture systems grow fish in tanks on land, which removes the sea lice problem, eliminates escape risk, allows siting near markets, and avoids marine licensing entirely.

They also require pumping and treating enormous volumes of water, which is energy intensive, and capital cost per unit of capacity far exceeds a sea site.

Several ambitious projects have failed or substantially underperformed, generally from biological problems in the closed system rather than from the economics. The technology works at smaller scale and the commercial viability at large scale remains unproven, which is a similar position to controlled environment agriculture.

The Bottom Line

Farmed salmon converts feed into protein more efficiently than any land animal, for biological reasons no terrestrial producer can replicate, and that advantage is the foundation of the industry. What limits it is not economics but sea lice, disease, and the small number of coastal sites where the conditions and the licences exist. The two year production cycle makes supply unresponsive to price, and fair value accounting on fish still in the water means reported earnings move before anything is sold.