ABSTRACT

The commercially significant Foveaux Strait Ostrea chilensis fishery has been typified by consistently low brooding rates and recruitment failures since recurrent mass mortalities from Bonamia exitiosa infection. The present study examined the gametogenic cycle of Foveaux Strait O. chilensis monthly, from July 2017 to September 2018, using histological examination of the gonad and condition indices to determine resulting changes to gametogenesis, spawning, brooding, and spatial variation, compared to an initial study of reproduction before B. exitiosa epidemics. The seasonal gametogenic cycle and brooding period were similar to previous descriptions. However, there was evidence for a more female skewed sex ratio, and the development and release of ova into the mantle cavity at smaller sizes. Despite similarities in gametogenesis, sex ratios, temperature, and chlorophyll-a concentrations between five sites across Foveaux Strait, the western-most site had no brooders and consistently lower condition indices, compared to the eastern-most site. Oysters may need to be in sufficient condition to initiate brooding, and reduced male densities may contribute to sperm limitation, which, along with a disconnect between the peak release of gametes and brooding, may have contributed to lower brooding rates.

摘要

具有商业意义的 Foveaux 海峡牡蛎渔业的特点是育雏率持续低下，并且由于博纳米虫感染导致反复出现大规模死亡，因此招募失败。本研究从 2017 年 7 月至 2018 年 9 月每月检查 Foveaux Strait O. chilensis 的配子发生周期，使用性腺和条件指数的组织学检查来确定配子发生、产卵、育雏和空间变异的变化，与初始相比。B. exitiosa之前的繁殖研究流行病。季节性配子发生周期和育雏期与之前的描述相似。然而，有证据表明女性的性别比例更加偏斜，并且卵子的发育和释放到地幔腔中的尺寸较小。尽管福沃海峡的五个地点之间的配子发生、性别比例、温度和叶绿素a浓度相似，但与最东部的地点相比，最西边的地点没有育雏器，并且状况指数始终较低。牡蛎可能需要处于足够的条件才能开始育雏，雄性密度的降低可能会导致精子限制，再加上配子释放峰值与育雏之间的脱节，可能会导致育雏率降低。