Kevan L. Main

Embryonic and Early Larval Development in Hatchery-Reared Common Snook

Abstract To gain an improved understanding of the early life history of common snook Centropomus undecimalis and refine hatchery production techniques for this species, a combination of digital photography and histological techniques were used to document the embryonic and early larval development of hatchery-reared individuals. Embryo development from fertilization to hatching took 15 h at 28°C. Larvae at 2 d posthatch showed fully pigmented eyes, and histological sections of the digestive tract revealed the presence of cellular structures indicative of a functional gut. This suggests that common snook larvae have the mechanical ability to detect, capture, and digest prey at 2 d posthatch. Received November 10, 2011; accepted February 14, 2012

Severe glomerular disease in juvenile grey snapper Lutjanus griseus L. in the Gulf of Mexico caused by the myxozoan Sphaerospora motemarini n. sp.

Graphical abstract

Microalgae (diatom) production — The aquaculture and biofuel nexus

As fishing has become more industrialized and wild fish stocks increasingly depleted, aquaculture production has grown rapidly to address the shortfalls in capture fisheries and limitations to long-term aquaculture success. One such shortfall is the need to produce a suitable, sustainable, substitute for the capture fishery derived fish meal and oil based fish feeds currently in use, while maintaining the human protein requirements and health benefits of Long Chain (LC) omega-3 oils in farmed fish products. Fish derive the LC omega-3 oils from the food they consume, which ultimately comes from lower trophic level primary producers like microalgae. Using Integrated Aquaculture System (IAS) principles and practices, microalgae (diatoms) can be raised and processed directly for their Algal/Single Cell Oils (SCO), protein, and nutrients. Besides the use as an aquaculture feedstock, microalgae have been investigated for biofuel production because of higher photosynthetic efficiency, higher biomass production, and faster growth compared to other terrestrial energy crops. SCO based carbon-neutral renewable liquid biofuel solutions are currently under investigation but suffer from high production costs. Liquid biofuels have been considered to displace non-renewable, petroleum-derived transport fuels of limited availability which contribute to climate change via greenhouse gas (GHG) emissions. The current high cost constraint of SCO production could be alleviated through explored water-energy-food nexus synergies between the aquaculture and biofuels sector with a concentration on innovations in microalgae/SCO production, harvesting, and processing technologies. Interdisciplinary collaborations between engineers, biologists and chemists are essential for their successful development.

Biological denitrification in marine aquaculture systems: A multiple electron donor microcosm study

There is a lack of information on denitrification of saline wastewaters, such as those from marine recirculating aquaculture systems (RAS), ion exchange brines and wastewater in areas where sea water is used for toilet flushing. In this study, side-by-side microcosms were used to compare methanol, fish waste (FW), wood chips, elemental sulfur (S0) and a combination of wood chips and sulfur for saline wastewater denitrification. The highest denitrification rate was obtained with methanol (23.4 g N/(m3·d)), followed by FW (4.5 g N/(m3·d)), S0 (3.5 g N/(m3·d)), eucalyptus mulch (2.6 g N/(m3·d)), and eucalyptus mulch with sulfur (2.2 g N/(m3·d)). Significant differences were observed in denitrification rate for different wood species (pine > oak ≫ eucalyptus) due to differences in readily biodegradable organic carbon released. A pine wood-sulfur heterotrophic-autotrophic denitrification (P-WSHAD) process provided a high denitrification rate (7.2-11.9 g N/(m3·d)), with lower alkalinity consumption and sulfate generation than sulfur alone.