Salinity Preference in the Estuarine Teleost Fish Mummichog (Fundulus heteroclitus): Halocline Behavior

Area of Science:

• * Ecology and Environmental Biology
• * Ichthyology and Fish Behavior

Background:

• * Mummichogs (Fundulus heteroclitus) exhibit adaptability to varying temperatures and salinities.
• * Seasonal movements of estuarine fish are influenced by environmental factors like temperature and salinity.

Purpose of the Study:

• * To investigate the environmental drivers of mummichog migration into estuarine shallows.
• * To determine salinity and temperature preferences of mummichogs in field and laboratory settings.
• * To understand the role of reproductive maturation in mummichog habitat selection.

Main Methods:

• * Field observations using minnow trapping to assess mummichog distribution in relation to temperature and salinity.
• * Laboratory experiments using artificial haloclines to test salinity preference under controlled temperature conditions.
• * Comparison of mummichog behavior with that of three-spine sticklebacks (Gasterosteus aculeatus).

Main Results:

• * Mummichogs exhibit aversion to cold temperatures and high salinities, preferring warmer, low-salinity waters in early spring.
• * Field studies showed mummichogs appearing in shallows above 10°C and increasing in abundance up to 21°C.
• * Laboratory tests revealed that while males consistently prefer seawater (SW), mature females show no significant salinity preference, readily entering low-salinity water.

Conclusions:

• * The seasonal migration of mummichogs into low-salinity estuarine areas is primarily influenced by female reproductive status and their preference for warmer water.
• * Mummichog habitat selection is a complex interplay of temperature, salinity, and reproductive physiology.
• * Females' lack of salinity preference facilitates movement into crucial summer breeding grounds.