Fish Growth Projection

The Thermal Growth Coefficient model this calculator uses -- the named growth model described in Jobling (2003), "The thermal growth coefficient (TGC) model of fish growth: a cautionary note," Aquaculture Research 34(7) -- treats growth as proportional to accumulated temperature over time, so warmer water directly speeds up the projected growth rate. At default settings, raising Water Temperature from 8C to 32C cuts the projected days to market by roughly three-quarters. This only holds within a species' real thermal tolerance — the formula has no built-in ceiling for temperatures that would actually stress or harm the fish.

Yes — they enter the underlying formula the same way, both sitting in the same denominator, so nudging either one by the same percentage moves Days to Market Weight by roughly the same amount. Thermal Growth Coefficient (TGC) is a species- and often strain- specific growth constant (the calculator's helper text lists rough typical values: tilapia around 2.5, trout around 1.5, catfish around 2.0, salmon around 1.8), not something a farmer adjusts operationally the way they can adjust water temperature.

Days to Market Weight is proportional to the remaining growth needed, measured as the difference between the cube roots of target and current weight. A fish that starts heavier already has less growth left to complete before reaching the target, so Days to Market Weight decreases as Current Fish Weight increases, holding everything else fixed.

The calculator can't project negative growth, so instead of erroring it silently raises the effective target to one gram above Current Fish Weight before computing Days to Market Weight — which then comes out flat and near-zero rather than genuinely responding to whatever value you entered. Check the Target Weight Adjusted result: it reads "Yes" and shows the adjusted value whenever this substitution happened, so you know the displayed projection isn't based on your original Target Market Weight input.

It applies a fixed feed conversion ratio of 1.5 (feed grams per gram of weight gained) regardless of species, feed brand, or water quality. Real feed conversion ratios in commercial aquaculture commonly range from about 1.0 to 2.5 depending on species and system efficiency, so this figure is a rough planning estimate rather than a species- specific feed budget.