What is the relationship between release size and survival of fish?

Introduction

The relationship between the size at release and the survival of fish is a critical factor in fisheries management and conservation efforts. Understanding how release size impacts survival rates can help optimize stocking strategies to enhance fish populations and ensure sustainable practices.

Key Insights

Size-Dependent Survival:
- Larger fish at release generally have higher survival rates compared to smaller fish. This trend is observed across various species, including white sturgeon, steelhead, and Chinook salmon .
- For white sturgeon, smaller fish (<25 cm fork length) showed significantly lower first-year survival rates compared to larger individuals.
- In steelhead, monthly mortality rates were inversely related to size at stocking, indicating that larger fry had better survival rates.
- Chinook salmon released at larger sizes (greater than 17 g or 120 mm fork length) by July had higher marine survival rates.
Density-Dependent Effects:
- High stocking densities can negatively impact survival rates due to increased competition and resource limitations. This was evident in white sturgeon, where survival rates declined with higher juvenile abundance.
- For sea cucumbers, survival was density-independent within the experimental range, but growth was density-dependent, suggesting that optimal stocking densities are crucial for maximizing survival and growth.
Temporal Factors:
- The timing of release also plays a significant role in survival. For instance, steelhead fry released earlier in the season had higher growth rates, although survival rates were more closely tied to size at release.
- Coho salmon released later in the season showed better marine survival, indicating that release timing can influence survival outcomes.
Site-Specific Variability:
- Survival rates can vary significantly among different release sites due to local environmental conditions and habitat suitability. This was observed in sea cucumbers, where site-specific factors influenced survival rates.
- For Chinook salmon, local conditions during the spring and summer were crucial for survival, highlighting the importance of site-specific management strategies.

Conclusion

The survival of fish post-release is strongly influenced by the size at release, with larger individuals generally exhibiting higher survival rates. Additionally, factors such as stocking density, release timing, and site-specific conditions also play significant roles in determining survival outcomes. Effective fisheries management should consider these variables to optimize stocking strategies and enhance fish population sustainability.

What is the relationship between release size and survival of fish?

Summary

Introduction

Key Insights

Conclusion

Sources and full results

Evidence of density- and size-dependent mortality in hatchery-reared juvenile white sturgeon (Acipenser transmontanus) in the Kootenai River

Density and size-dependent mortality in hatchery-reared juvenile white sturgeon in the Kootenai River suggest that releasing fewer, larger-sized fish may improve first-year survival rates and recruitment to the spawning-age population.

Effects of Size at and Time of Release on the Survival and Growth of Steelhead Fry Stocked in Streams

Steelhead fry survival and growth rates are inversely related to stocking size and release time, with early-stocked, small fry showing higher growth rates than later-stocked, larger fry.

Spatio-Temporal and Size-Dependent Variation in the Success of Releasing Cultured Sea Cucumbers in the Wild

Released juveniles of 3g or larger in optimal habitat can survive to market size, with 7-20% surviving to market size in optimal habitat.

Survival, Ocean Growth, and Ocean Distribution of Differentially Timed Releases of Hatchery Coho Salmon (Oncorhynchus kisutch)

Marine survival of hatchery coho salmon improves with release date, but early released fish grow as fast in early ocean life as later released fish, suggesting poor survival is not related to lack of food at early ocean life.

Rapid growth in the early marine period improves the marine survival of Chinook salmon (Oncorhynchus tshawytscha) in Puget Sound, Washington

Rapid growth in the early marine period improves the marine survival of Chinook salmon in Puget Sound, with larger sizes leading to higher survivals.

RELATING SIZE OF JUVENILES TO SURVIVAL WITHIN AND AMONG POPULATIONS OF CHINOOK SALMON

Survival in juvenile chinook salmon populations is strongly related to relative length, but not to relative condition index, suggesting that monitoring only a portion of their life history may provide incomplete information on survival variability.

Allometry of natural mortality as a basis for assessing optimal release size in fish-stocking programmes

The study found a consistent allometry that applies to fish-stocking programs, with the relative survival advantage of stocking large fish increasing with the level of mortality at reference length.

Size-Selective Mortality in Young-of-the-Year Yellow Perch (Perca flavescens): Evidence from Otolith Microstructure

Larger and faster-growing young-of-the-year yellow perch are more likely to survive intense predation pressure, while slower-growing populations experience minimal size-selective mortality.

The role of coastal ocean variation in spatial and temporal patterns in survival and size of coho salmon (Oncorhynchus kisutch)

Mixed-layer depth and sea level are the most important environmental variables influencing coho salmon survival and adult size, with shallow mixed layers increasing survival and decreasing size in all regions studied.

Relationship between marine growth and sea survival of two anadromous salmonid fish species

Growth during the sea sojourn and return rates are positively correlated, linking increased survival with growth in Arctic char and brown trout.

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