Fish Tag Recapture Length Increment Tool

Description

Subtract releaseLength from recaptureLength, divide by positive days, and multiply dailyIncrement by 365 for annualizedIncrement.

Age and growth records compare reader estimates, increments, lengths, and observation intervals. A numeric difference or back-calculation depends on the chosen origin and model rather than establishing the animal's true age.

Subtract releaseLength from recaptureLength, divide by positive days, and multiply dailyIncrement by 365 for annualizedIncrement.

When to use this tool

Use Fish Tag Recapture Length Increment when you need one supplied age or growth-record component.

How to use the tool and how it works

Enter releaseLength, recaptureLength, days. Use the units and conventions below.
Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
Read increment, dailyIncrement, annualizedIncrement. Use the output convention below.

Subtract releaseLength from recaptureLength, divide by positive days, and multiply dailyIncrement by 365 for annualizedIncrement.^[1]

Input field	Meaning and units	Accepted input
releaseLength	Release Length	Required. Finite number; minimum 0.
recaptureLength	Recapture Length	Required. Finite number; minimum 0.
days	Days	Required. Finite number; strictly above 0.

Output field	Interpretation	Returned shape
increment	Increment	Required. Finite number.
dailyIncrement	Daily Increment	Required. Finite number.
annualizedIncrement	Annualized Increment	Required. Finite number.

json

{
  "input": {
    "releaseLength": 100,
    "recaptureLength": 118,
    "days": 90
  },
  "output": {
    "increment": 18,
    "dailyIncrement": 0.2,
    "annualizedIncrement": 73
  }
}

Limitations and assumptions

Lengths are nonnegative and use one unit; signed growth is retained and annualization is a constant-rate rescaling, not a growth prediction or actual calendar-year correction.
Inputs must satisfy both the field types and the cross-field conditions above. Invalid input causes an error; a successful false flag or documented placeholder is a different result.
Numeric calculations use binary floating point unless exact decimal-integer arithmetic is explicitly stated. No hidden measurement tolerance or decimal rounding is added; nonfinite or out-of-contract results are rejected. Numeric signed-zero results are exported as zero.

Alternative or Complementary methods

Review aging validation, measurement landmarks, sampling, and the species-specific growth assumptions separately.

References

Calculation and input contract: ichthyology/fish-tag-recapture-length-increment — tool.io

Similar or alternative tools

Otolith Two Reader Age Gap
Return second minus first age, their mean, and mean minus referenceAge.
Fish Morphometric Size Standardization Term
Multiply measurement by (referenceLength/fishLength) raised to allometricExponent and return that factor separately.