Variation in egg mass within two Atlantic herring Clupea harengus stocks

Area of Science:

• Marine Biology
• Fisheries Science
• Ichthyology

Background:

• Herring (Clupea harengus) egg size is a critical factor influencing larval survival and recruitment.
• Understanding variation in egg size is essential for effective fisheries management and stock assessment.

Purpose of the Study:

• To determine if egg size (mass) is invariant in Scotia-Fundy summer and autumn (SFSH) and Icelandic summer (ISSH) spawning herring stocks.
• To investigate the relationship between maternal characteristics and egg mass variation.

Main Methods:

• Oocyte dry mass and volume measurements were conducted on herring from SFSH and ISSH stocks.
• Histological examination of ovaries was performed for ISSH samples.
• Statistical analysis was used to assess the variation in egg mass and its correlation with maternal body mass and length.

Main Results:

• Significant variation in egg dry mass (up to twofold) was observed among individual fish within both SFSH and ISSH herring stocks.
• Maternal whole-body mass and total length explained approximately 20% of the variation in egg mass.
• Oocyte volume measurements corroborated the findings from dry mass analysis.

Conclusions:

• Herring egg size is not invariant within SFSH and ISSH stocks, exhibiting substantial individual variation.
• Maternal body size is a significant, but not sole, determinant of egg mass.
• Fisheries management should prioritize maintaining a broad age composition in herring stocks to support recruitment success.