University of New England

Little Skate Egg Viability

Brittany Palm

Class of 2009

Very little information concerning the effects of temperature on the gestation rates of skate egg cases exists in the primary literature.  This is particularly true for those species that have a protracted egg-laying season, such as the little skate, L. erinacea.  Anecdotal data suggests that gestation rates in this species may vary based on the season of oviposition.  This research project focuses on comparing the gestation and growth rates of little skate embryos that were laid in the summer to those laid in the fall of 2007.  Moreover, we are also interested in examining the success rate of these embryonic skates as they progress towards hatching.  In our study, two groups of mature female skates have been kept in captivity.  The first group (Group A) of mature females are being maintained with mature males and the second group (Group B) have been isolated to examine the capacity for sperm storage in this species.  The presence of egg cases is monitored on a daily basis in each adult tank.  When egg cases are observered, they are collected and categorized by week of oviposition.  Egg cases are examined for viability at three-week intervals and any unfertilized eggs are documented and then disposed of.  All egg cases are maintained in shallow tanks equipped with flowing seawater.  This system allows for natural variation in environmental temperatures to consider the seasonal effects on the gestation rates of this species.  SInce the study's inception (May 2007), 343 egg cases have been collected from both groups of mature female skates (176 eggs Group A and 167 eggs Group B).  Preliminary data suggests that a peak in egg laying occurs during the month of October.  Preliminary  data also suggests that Group A currently has a viability rate of 83.7% while the isolated females of Group B have a viability rate of 68.1%.  The isolated females are of a particular interest because sperm storage has never been studied in this elasmobranch species.  Further data will give insight to the length of sperm storage viability.  This study is unique because previous studies have examined fecundity and gestation rates in controlled environments.  If seasonal differences in growth and gestation rates do exist in this species, this anomaly could have an impact on the little skates' ability to rebound from fishing pressure within the Gulf of Maine.  Furthermore, the viability data will provide a more accurate measurement for recruitment rates and population restoration.

For more information about the project email Brittany
bpalm@mail.une.edu
or Dr. Sulikowski
jsulikowski@une.edu

1 Month into Gestation

3 Months into Gestation

5 Months into Gestation