Length changes in herring (Clupea harengus) larvae: Effects of capture and storage in formaldehyde and alcohol

The effects on standard length of storing laboratory-reared larval herring (9-19 mm live length) in 4% buffered formaldehyde or 70% buffered ethanol with and without simulated capture by towed net were assessed. Lengths during storage were considered stable after 15 days for larvae placed directly in formaldehyde, and after 30 days for larvae placed directly into alcohol or for larvae treated by net-capture simulation before storage. The following linear regressions described the relationships between live length and the stored lengths of larvae after these times: for larvae stored directly in formaldehyde, L = 1.765 + 0.867 x X(1); for larvae stored directly in alcohol, L = 0.564 + 0.971 x X(1); for larvae subjected to net-capture simulation then stored in formaldehyde, L = 0.984 + 0.993 x X(1); and for larvae subjected to net-capture simulation then stored in alcohol, L = 0.532 + 0.989 x X(1), where L = live standard length and X(1) = standard length after storage. The non-linear regression formula parameterized by Theilacker (Fish. Bull. US, 78, 685-692, 1980) for northern anchovy larvae provided a good fit to the data for herring larvae subjected to net-capture simulation and then stored in formaldehyde. However, the model had to be re-parameterized to provide a good fit for larvae stored in alcohol. The precision achieved in length measurements using a computer-aided measuring system is also discussed.