Presentation Title

Hatching Success of California Grunion, Leuresthes tenuis, in Response to Increased Temperature and Decreased Sand Humidity

Start Date

November 2016

End Date

November 2016

Location

HUB 302-143

Type of Presentation

Poster

Abstract

California Grunion, Leuresthes tenuis, is a beach-spawning fish that deposits its eggs in beach sand, where they may be more susceptible to a warmer and drier environment than eggs in the ocean. I hypothesize that both low sand humidity and increased temperature will decrease hatching success in California Grunion. Ten clutches of eggs were collected after a Grunion Run and divided into four conditions: 20°C and 28°C, and normally hydrated or dehydrated. Eggs were tested every day for hatching competence beginning on day 6 post-spawning. From each treatment during primary and delayed hatching periods, 100 eggs were tested for hatching success. Sand water content was monitored daily in the lab, and in the field every third day. Increased temperature accelerated development, but reduced delayed hatching success. Hydration was necessary for successful hatching. The groups that had over 50% hatching were both cold and warm wet eggs in the primary period, and cold and wet eggs in the delayed period; all other groups experienced below 50% hatching success. Additionally, warm dehydrated eggs completely died 9 days post-spawning. Wet lab sand samples mimicked field conditions, while dry lab sand samples had significantly less water. Warm and dry sand had less water than cold and dry sand. Finally, the 10 cm deep sand temperature at one time of day averaged to 19.7°C, mimicking cold lab conditions. Thus, temperate, hydrated conditions are most favorable for grunion eggs. Dryness particularly when associated with increased temperature poses a threat to the viability of grunion eggs.

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Hatching Success of California Grunion, Leuresthes tenuis, in Response to Increased Temperature and Decreased Sand Humidity

HUB 302-143

California Grunion, Leuresthes tenuis, is a beach-spawning fish that deposits its eggs in beach sand, where they may be more susceptible to a warmer and drier environment than eggs in the ocean. I hypothesize that both low sand humidity and increased temperature will decrease hatching success in California Grunion. Ten clutches of eggs were collected after a Grunion Run and divided into four conditions: 20°C and 28°C, and normally hydrated or dehydrated. Eggs were tested every day for hatching competence beginning on day 6 post-spawning. From each treatment during primary and delayed hatching periods, 100 eggs were tested for hatching success. Sand water content was monitored daily in the lab, and in the field every third day. Increased temperature accelerated development, but reduced delayed hatching success. Hydration was necessary for successful hatching. The groups that had over 50% hatching were both cold and warm wet eggs in the primary period, and cold and wet eggs in the delayed period; all other groups experienced below 50% hatching success. Additionally, warm dehydrated eggs completely died 9 days post-spawning. Wet lab sand samples mimicked field conditions, while dry lab sand samples had significantly less water. Warm and dry sand had less water than cold and dry sand. Finally, the 10 cm deep sand temperature at one time of day averaged to 19.7°C, mimicking cold lab conditions. Thus, temperate, hydrated conditions are most favorable for grunion eggs. Dryness particularly when associated with increased temperature poses a threat to the viability of grunion eggs.