Fecundity in ripe gonad of Haliotis fulgens and Haliotis corrugata (Vetigastropoda)

Abstract

Background: The term fecundity in abalone is defined according to an estimate of its absolute fecundity, which is the number of mature oocytes present in the gonad, or as potential fecundity, i.e., the total number of oocytes present in the gonad. In Mexico, few studies have estimated the fecundity of mollusks and these have been performed on gonads in different phases of gonadal development, obtaining values that are very different or overestimated, for example, values ranging from 80000 to 22 million oocytes in a gonad. Goals: Estimate the fecundity of Haliotis fulgens (blue abalone) and Haliotis corrugata (yellow abalone), using ma­ture gonads and a particle counter (Multisizer 3) to count only mature oocytes. Methods: Each month from October 2011 to February 2013, 30 adult organisms of each species were collected in two localities of Baja California Sur, Mexico (La Bocana and Bahía Tortugas). A histological analysis identified those that were mature females. To obtain the number of eggs per gram, triplicate oocyte counts were performed in a coulter counter Multisizer 3, in a solution of 4 g wet weight of mature oocytes diluted to 50 mL of filtered seawater (μm). Absolute fecundity was calculated by multiplying the total weight of the gonad by the number of mature oocytes present in one gram of oocytes. Results: The fecundity in La Bocana was found to be 2x106 eggs in H. corrugata and H. fulgens, while in Bahia Tortugas it was 4x106 eggs in H. fulgens. Conclusions: This study suggests that estimating absolute fecundity in species with partial spawning, such as H. fulgens and H. corrugata, should be per­formed on all females regardless of the degree of gonadal development. However, only mature oocytes should be considered as an indicator of absolute fecundity. Therefore, the use of an apparatus that counts and measures mature oocytes, such as a particle counter, facilitates and guarantees a good estimate of fecundity.