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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. [ABSTRACT FROM AUTHOR]

Blue mussels, Mytilus galloprovincialis, are a widespread and ecologically important species in New Zealand coastal ecosystems, yet, there is limited information on the seasonality and variability in reproduction among populations. The reproductive cycle of M. galloprovincialis was studied monthly over 1-year in two southern New Zealand populations (Aramoana (45.7787°S, 170.7037°E) and Timaru (44.3905°S, 171.2498°E)). Tissue indices were determined, and gonads examined histologically. At both sites, males and females displayed synchronous changes in condition indices and gonad indices, with both indices generally greater in the Timaru population than in the Aramoana population. Both sampling sites presented with comparable seasonality of reproduction with spawning over spring and summer months (September to February). Gametogenic development occurred over the autumn and early-winter period (March to August). Spatial differences in reproduction coincided with differences in phytoplankton food abundance (greater in Timaru), while there were only small differences in sea temperatures between sites. This study indicates the likelihood of spatial variation in reproductive biology between M. galloprovincialis populations, even across small spatial scales (<200 km). [ABSTRACT FROM AUTHOR]

The genus Nyctiphanes G.O. Sars, 1883 (Euphausiacea, Euphausiidae) includes four extant species. These species are a conspicuous component of trophic webs of coastal marine ecosystems due to their abundance, the formation of dense aggregations, swarms, and schools, fast growth, and high reproductive rates. They dominate the bulk biomass in eutrophic Eastern Boundaries System and subtropical mesotrophic habitats, with estimates of 30–40% of the total zooplankton biomass. Species of Nyctiphanes are efficient omnivores and conversely prey for a large number of zooplanktonic and nektonic species. We review current knowledge of the biogeography, reproductive biology, physiology, biochemistry, ecology, and parasitology of the four species of Nyctiphanes. Most published information on Nyctiphanes focuses on the two species from the Pacific Ocean, N. australis G.O. Sars, 1883 and N. simplex   Hansen, 1911 , and considerably less is known on the biology and ecology of N. couchii (Bell, 1853) and N. capensis   Hansen, 1911 from the Atlantic Ocean. Knowledge on the biology and ecology of the species of Nyctiphanes is still behind what is currently known for species of krill, particularly compared to Euphausia   Dana, 1850 and Thysanoessa   Brandt, 1851 , and new multi-focal studies on the effects that environmental variables have on reproductive aspects, survival, growth, and physiology are especially critical to address under future environmental change. [ABSTRACT FROM AUTHOR]