Shrimp inbreeding: a risk is not a diagnosis

Inbreeding concerns reproduction between relatives. It cannot be established merely from colour, body size or a smaller clutch. Relatedness may matter in a closed breeding group, but disappointing aquarium outcomes do not establish it as the cause.

Species-specific research exists

Tropea, Marciano and López Greco compared full-sibling with non-brother matings in N. davidi. After one generation, fewer juveniles hatched in the related group, while egg production and fertilisation success did not differ. Some later outcomes also differed with stage and conditions. This demonstrates an effect in that experiment, not a fixed boundary for every hobby line.

Responding to a declining colony

1. Describe the problem precisely: fewer eggs, fewer hatchlings, slower growth or deaths. Identify estimated counts.
2. Investigate water, food access, predation, recent changes and health. These checks remain necessary when relatedness is known.
3. Examine parent and origin records. A large group may largely be one family; another shop may use the same source.
4. Seek suitable help for persistent problems and share the records. Do not blindly add animals instead of investigating.

There is no established calendar rule here requiring yearly “new blood”. Additions can bring unknown relatedness, disease and unwanted mixing. Read how to prepare that decision and preserve existing records. A good-looking line has not thereby passed a genetic health test.

Sources and scope

• Tropea, Marciano & López Greco (2022): Brothers are better than nothing
• Tave, FAO (1999): Effective breeding number
• LICG: Zoetwatergarnaal

Tropea and colleagues’ findings were read in the publisher-indexed author abstract. The experiment concerns one generation of full-sibling mating in laboratory N. davidi. FAO addresses fish broodstock; no fish threshold is adopted as a shrimp guideline.