Jane E. Symonds

An Integrated Approach to Gene Discovery and Marker Development in Atlantic Cod (Gadus morhua)

Atlantic cod is a species that has been overexploited by the capture fishery. Programs to domesticate this species are underway in several countries, including Canada, to provide an alternative route for production. Selective breeding programs have been successfully applied in the domestication of other species, with genomics-based approaches used to augment conventional methods of animal production in recent years. Genomics tools, such as gene sequences and sets of variable markers, also have the potential to enhance and accelerate selective breeding programs in aquaculture, and to provide better monitoring tools to ensure that wild cod populations are well managed. We describe the generation of significant genomics resources for Atlantic cod through an integrated genomics/selective breeding approach. These include 158,877 expressed sequence tags (ESTs), a set of annotated putative transcripts and several thousand single nucleotide polymorphism markers that were developed from, and have been shown to be highly variable in, fish enrolled in two selective breeding programs. Our EST collection was generated from various tissues and life cycle stages. In some cases, tissues from which libraries were generated were isolated from fish exposed to stressors, including elevated temperature, or antigen stimulation (bacterial and viral) to enrich for transcripts that are involved in these response pathways. The genomics resources described here support the developing aquaculture industry, enabling the application of molecular markers within selective breeding programs. Marker sets should also find widespread application in fisheries management.

Developing yellowtail kingfish (Seriola lalandi) and hāpuku (Polyprion oxygeneios) for New Zealand aquaculture

Two high value species, yellowtail kingfish (Seriola lalandi) and hāpuku (groper, Polyprion oxygeneios), have been identified as suitable new candidates for New Zealand aquaculture. This paper reviews the research by NIWA and collaborators conducted to test the biological, technological and economic feasibility of farming these two species. NIWA now has the capability to produce sufficient kingfish fingerlings per year to meet the needs of the early stages of an industry. Advances in hāpuku aquaculture have also been significant, from spawning in captivity through to the selection of juveniles for improved growth. Recently, the first spawning of captive hāpuku F1 broodstock and production of F2 eggs, larvae and juveniles was achieved. Although hāpuku larval survival remains variable, the ability to close the life cycle, and the availability of domesticated broodstock, provide a significant step forward and increase the chances of this species being commercially farmed.

Genetic improvement of New Zealand aquaculture species: programmes, progress and prospects

Aquaculture, like terrestrial farming, cannot achieve economic and sustainable production without high performing genetic stocks tailored to the conditions under which they are grown. It is essential, therefore, that aquaculture investment includes genetics and biotechnology to adapt marine livestock to the novel conditions of intensive aquaculture and to the demanding markets into which they are sold. The return on investment in well-structured breeding programmes can be very high, and significant performance and economic gains have been demonstrated in multiple species. Many factors must be considered in designing a genetic improvement programme, including the reproductive biology of the species and the identification of realistic and commercially relevant breeding goals based on the resources and facilities available. This paper reviews the options available to aquaculturists and provides examples of how these are being applied to six aquaculture species in New Zealand: king salmon, hāpuku, kingfish, GreenshellTM mussels, Pacific oysters and pāua (abalone).

Early development of New Zealand hapuku Polyprion oxygeneios eggs and larvae

This study describes for the first time the normal development of New Zealand hapuku Polyprion oxygeneios embryos and larvae reared from fertilization to 11 days post-hatch (dph) at a constant temperature. Fertilized eggs were obtained from natural spawnings from communally reared captive wild broodstock. Eggs averaged 2 mm in diameter and had single or multiple oil globules. Embryos developed following the main fish embryological stages and required an average of 1859·50 degree hours post-fertilization (dhpf) to hatch. The newly hatched larvae (4·86 mm mean total length, L(T) ) were undifferentiated, with unpigmented eyes, a single and simple alimentary tube and a finfold that covered the entire body. Larvae relied on the energy from the yolk-sac reserves until 11 dph (7·33 mm mean L(T) ), when yolk-sac reabsorption was almost completed. Some of the major developmental stages from hatching to yolk-sac reabsorption were eye pigmentation (5 dph), upper jaw formation (7 dph), lower jaw formation (8 dph) and mouth opening (8-9 dph). By 9 dph, the digestive system consisted of pancreas, liver, primordial stomach, anterior and posterior gut; therefore, P. oxygeneios larvae would be capable of feeding on live prey. The developmental, morphological and histological data described constitutes essential baseline information on P. oxygeneios biology and normal development.

Molecular and biochemical tricks of the research trade: -omics approaches in finfish aquaculture

Profitability of fish farming can be undermined by a suite of biological constraints. Effects of these constraints on the biology of the animal, the functioning of a tissue, or the quality of the final filleted product can be detected with very sensitive hi-tech approaches, grouped by the term ‘-omics’. These -omics technologies further present powerful tools for the genetic selection of diverse traits and, as such, will contribute substantially to the future development of the aquaculture sector. Sustainability issues of importance to the industry, such as environmental impacts, use of therapeutants, fish health management and fishmeal replacement, can again be aided, at least in part, through the effective use of -omics technologies. It thus appears that -omics technologies may be a key tool for the responsible growth of intensive aquaculture in the 21st century. In this paper we review the current status of -omics technologies and the potential for application within the aquaculture industry.

The effects of 11-ketotestosterone on ovarian physiology of previtellogenic captive hapuku (Polyprion oxygeneios)

The present study investigated, for the first time in a perciform teleost, the effects of in vivo 11-ketotestosterone (11-KT) treatment using slow-release implants on ovarian development and gonadotropin receptor mRNA levels in captive previtellogenic females of hapuku (Polyprion oxygeneios). At the cellular/functional level, ovarian development and ovarian and hepatic total lipid levels were examined. At the molecular level, transcript abundance of ovarian follicle-stimulating hormone receptor (FSH-R) and luteinizing hormone receptor (LH-R) was measured. Additionally, cyclic adenosine monophosphate (cAMP) levels in ovarian fragments from placebo and 11-KT implanted fish incubated with or without human chorionic gonadotropin (hCG) in vitro were compared between groups. There were no significant differences between treatments with regard to oocyte size and lipid contents of liver and ovary. Messenger RNA levels of FSH-R and LH-R were significantly lower in the treated females. Similarly, cAMP levels were significantly lower in the ovarian fragments of the 11-KT implanted females. These results suggest that 11-KT specifically, but possibly androgens in general, may not have an important function in regulating gonadal development of previtellogenic female hapuku; indeed, if anything, 11-KT appeared to have a detrimental effect and its use will not be beneficial in advancing sexual maturity of hapuku in aquaculture.

Male–female relatedness at specific SNP-linkage groups influences cryptic female choice in Chinook salmon (Oncorhynchus tshawytscha)

In a range of taxa, the relatedness between mates influences both pre- and post-mating processes of sexual selection. However, relatively little is known about the genetic loci facilitating such a bias, with the exception of the major histocompatibility complex. Here, we performed tightly controlled replicated in vitro fertilization trials to explore the impact of relatedness on two possible mechanisms of cryptic female choice (CFC) in Chinook salmon (Oncorhynchus tshawytscha). We tested (i) whether relatedness of mates, assessed using 682 single nucleotide polymorphisms (SNPs) on 29 SNP-linkage groups (LGs), biases a males sperm velocity in ovarian fluid (a parameter previously shown to predict male fertilization success), and (ii) whether relatedness of mates governs fertilization success via other mechanisms, probably via sperm–egg interactions. We found that relatedness on three LGs explained the variation in sperm velocity, and relatedness on two LGs explained fertilization success, which might indicate the presence of genes important in sperm–ovarian fluid and sperm–egg interactions in these genomic regions. Mapping of the SNPs on these LGs to the rainbow trout genome revealed two genes that affect fertility in humans and represent candidate genes for further studies. Our results thereby provide a novel contribution to the understanding of the mechanism of CFC.

Ovarian development of captive F1 wreckfish (hāpuku) Polyprion oxygeneios under constant and varying temperature regimes – Implications for broodstock management

In order to better understand how photo-thermal conditions affect oogenesis in captive-bred F1 hāpuku, a wreckfish considered for aquaculture in New Zealand, juvenile (pre-pubertal) fish were assigned to one of two regimes: exposed to a constant temperature of 17°C (CT group) or to seasonally varying temperatures (VT group range: 10-17°C), both under simulated ambient photoperiod, for nearly 2years. Development in females was monitored through repeated gonadal biopsies (histology; target gene mRNA levels) and blood sampling (plasma levels of estradiol-17β; E2). Very little evidence of advancing oogenesis was found in the first year of study, when fish were in their 4th year. In the subsequent year, a proportion of fish reached the pre-spawning stage (fully-grown ovarian follicles); the proportion of females reaching this stage was notably higher in the VT (62%) than the CT (28%) group. Of the few females that did reach maturity in the CT group, significantly lower levels of plasma E2 were observed relative to those in fish from the VT group possibly indicating a temperature-induced endocrine impairment during oogenesis. Interestingly, females that did not reach the pre-spawning stage presented with a small transient, but significant increase in oocyte diameters and plasma E2, suggestive of a dummy run. Clear seasonality was observed for fish under both photo-thermal regimes, and this was reflected in plasma E2 levels and transcript abundances of aromatase, fshr and luteinizing hormone receptor in the ovary; these end points all peaked in maturing females during the late or post-vitellogenic stage. We conclude that captive female F1 hāpuku first mature as five-year-olds and that exposure to a decreased temperature is important for appropriate progression of oogenesis.

Using near infrared spectroscopy to assess the composition of New Zealand aquaculture species

Near infrared spectroscopy has been employed to determine the proximate composition of Chinook salmon (Oncorhynchus tshawytscha) and Greenshell Mussels™ (Perna canaliculus). This work was presented at the Australian Near Infrared Spectroscopy Group and New Zealand Near Infrared Spectroscopy Society meeting in Rotorua, 11–12 April 2018, where it won the best overall presentation award for Near Infrared Science (Figure 1).

Vertebral abnormalities in free-living Chinook salmon (Oncorhynchus tshawytscha, Walbaum) in New Zealand

ABSTRACT Spinal abnormalities are common in farmed Chinook Salmon in New Zealand. We report spinal abnormalities in adult Chinook salmon which were predominantly hatchery reared and released as smolts and which we term free-living. We compare these to rates seen in farmed New Zealand salmon. 101 free-living adult salmon were radiographically assessed for spinal curvatures (lordosis, kyphosis, scoliosis; LKS) and other vertebral abnormalities. Severity of abnormality was assessed on a three-point scale. Abnormal vertebral bodies were detected in 88.1% of free-living salmon. Spinal curvatures were the most common abnormality type with 83.2% of fish showing this abnormality but only one free-living Chinook had LKS of severity greater than 1. Farmed Chinook salmon are reported to have LKS rates of 29% with 18% of LKS abnormalities of severity greater than 1. These results suggest that free-living Chinook salmon frequently develop spinal abnormalities, but these abnormalities are less severe than those observed in farmed salmon.