Please do not remove this page Evaluating spawning induction methods for the tropical black-lip rock oyster, Saccostrea echinata Nowland, Samantha; O'Connor, Wayne; Elizur, Abigail; et.al. https://research.usc.edu.au/discovery/delivery/61USC_INST:ResearchRepository/12142219730002621?l#13142219720002621 Nowland, S., O’Connor, W., Elizur, A., & Southgate, P. (2021). Evaluating spawning induction methods for the tropical black-lip rock oyster, Saccostrea echinata. Aquaculture Reports, 20, 1–10. https://doi.org/10.1016/j.aqrep.2021.100676 Document Type: Published Version Link to Published Version: https://doi.org/10.1016/j.aqrep.2021.100676 USC Research Bank: https://research.usc.edu.au [email protected] CC BY-NC-ND V4.0 © 2021 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license(http://creativecommons.org/licenses/by-nc-nd/4.0/). Downloaded On 2021/10/01 13:59:44 +1000 Please do not remove this page Aquaculture Reports 20 (2021) 100676 Contents lists available at ScienceDirect Aquaculture Reports journal homepage: www.elsevier.com/locate/aqrep Evaluating spawning induction methods for the tropical black-lip rock oyster, Saccostrea echinata Samantha J. Nowland a,b,*, Wayne A. O’Connor c, Abigail Elizur d, Paul C. Southgate b a Aquaculture Unit, Department of Industry, Tourism and Trade, Northern Territory Government, GPO Box 3000, Darwin, NT, 0801, Australia b School of Science, Technology & Engineering and Australian Centre for PacificIslands Research, University of the Sunshine Coast, 90 Sippy Downs Drive, Sippy Downs, Queensland, 4556, Australia c NSW Department of Primary Industries, Port Stephens Fisheries Institute, Taylors Beach, NSW, 2316, Australia d Genecology Research Centre, University of the Sunshine Coast, 90 Sippy Downs Drive, Sippy Downs, Queensland, 4556, Australia ARTICLE INFO ABSTRACT Keywords: When developing a species-specific hatchery protocol it is important to investigate the triggers for spawning, Spawning which is the foundation of the production cycle. This study evaluated multiple spawning induction techniques to Induction optimise the spawning success of black-lip rock oyster, Saccostrea echinata, broodstock. Initially, the most Oyster effective method for non-destructively opening broodstock was determined, to allow intramuscular injection of Saccostrea echinata chemical stimuli. Following this, the efficacy of seven spawning induction treatments, including two physical Salinity Muscle relaxant shock techniques, three chemical induction techniques, a combination of physical and chemical induction and strip spawning were assessed. Based on the outcomes of these trials, the combined and independent effects of reduced salinity and addition of sperm, as well as the potential of neuropeptides to trigger spawning, were evaluated. Results demonstrated that a concentration of 30 g/L of MgCl2 is an effective muscle relaxant for commercial and research application for S. echinata. It was determined that salinity reduction, rather than temperature increase, is a key factor for spawning induction. Strip spawning is a viable option for S. echinata; however, sperm motility was significantlyaffected, and fecundity and fertilisation rates were lower (although not significant,P > 0.05) when compared to other induction methods tested. A combination of physical and chemical induction, involving reduced salinity and addition of sperm, was the most successful treatment; 80 % of broodstock spawned within 19 min of salinity drop and addition of sperm. This method delivers significant production improvements for S. echinata, particularly regarding the time taken to induce spawning, and is therefore recommended for application in the hatchery. 1. Introduction year-round supply of spat (Maccacchero et al., 2005; FAO, 2011). Hatchery production has been established for Crassostrea iredalei and Oysters are a growing aquaculture commodity in tropical regions Crassostrea belcheri in Malaysia (Tan et al., 2014), Crassostrea angulata in that provide important economic and subsistence benefits in many Vietnam (O’Connor et al., 2016) and Crassostrea rhizophorae in Brazil countries (Nowland et al., 2019b; Willer and Aldridge, 2020). (Maccacchero et al., 2005). Other countries are progressing towards Commercial-scale production (>100 t per annum) occurs in Brazil, hatchery production by investing in species-specific research and northern Chile, southern China, Cuba, India, Indonesia, Malaysia, development, such as the establishment of culture techniques for Mexico, The Philippines, Senegal, Taiwan, Thailand and Vietnam Striostrea prismatica in Ecuador (Lodeiros et al., 2017). (Nezon, 1988; Huang and Lee, 2014; O’Connor et al., 2016; FAO, 2020). The black-lip rock oyster (Saccostrea echinata) (Quoy and Gaimard, Production in most of these countries, however, relies on collection of 1835) is an emerging aquaculture species that has received research wild spat as a source of culture stock, which can be unreliable (Nowland attention and investment. It occurs throughout the Indo-Pacific, from et al., 2019b). Research into hatchery production of tropical rock oysters Japan to New Caledonia, and across northern Australia, from Cone Bay is therefore increasing, stimulated by the need to guarantee a reliable, in Western Australia to Bowen in Queensland (Nowland et al., 2019d). * Corresponding author at: GPO Box 3000, Darwin, Northern Territory, 0801, Australia. E-mail addresses: [email protected] (S.J. Nowland), wayne.o’[email protected] (W.A. O’Connor), [email protected] (A. Elizur), [email protected] (P.C. Southgate). https://doi.org/10.1016/j.aqrep.2021.100676 Received 17 November 2020; Received in revised form 12 March 2021; Accepted 24 March 2021 Available online 7 April 2021 2352-5134/© 2021 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). S.J. Nowland et al. Aquaculture Reports 20 (2021) 100676 Recent research has focused on developing the potential of S. echinata as production for this developing aquaculture species. a new aquaculture commodity in tropical Australia (Cobcroft et al., 2020). Studies have investigated population genetics (McDougall, 2018; 2. Materials and methods Nowland et al., 2019d) and reproductive seasonality of wild oysters (Nowland et al., 2019c), described larval development (Southgate and 2.1. Broodstock and histology Lee, 1998; Nowland et al., 2018a) and optimised rearing conditions for larval growth and survival (Nowland et al., 2018b, a). However, there is Broodstock oysters (S. echinata) with length (dorsoventral measure­ a lack of information relating to methods for reliable spawning induc­ ment; DVM) and width (anteroposterior measurement; APM) of 100 ± tion, which is an important requirement for routine commercial hatch­ 1.99 mm and 74.49 ± 1.55 mm, respectively, were originally collected ◦ 0 00 ery production. Developing a hatchery protocol for a species new to from South Goulburn Island, Northern Territory, Australia (11 38 46 S ◦ 0 00 aquaculture usually involves trialling different methods for spawning 133 25 14 E) and held in earthen ocean filledponds near the Northern induction to identify the most effective method for the target species. Territory Government’s, Darwin Aquaculture Centre, for use when Successful spawning induction under hatchery conditions requires oys­ required. Broodstock were randomly collected from this population in ters with mature gametes (Li et al., 2010), which can be obtained December 2016 for Experiment 1 and February 2017 for Experiment 2. directly from the wild during periods of natural maturation (Nowland Some broodstock were used for both experiments, therefore, treatment et al., 2019c) or by conditioning broodstock within the hatchery numbers are provided for each experiment. Broodstock were rinsed with ´ (Chavez-Villalba et al., 2002; Maneiro et al., 2017). Spawning may be freshwater after collection and scrubbed clean of any fouling using an triggered by several endogenous and exogenous factors, and methods iodine solution; 10 mL of Providone-Iodine Antiseptic Solution into 10 L often involve chemical induction, physical shock (i.e. rapid change in an of freshwater. Broodstock length (mm), width (mm), height (mm) and environmental factor such as water temperature or salinity) or a com­ weight (g) were recorded before each experiment. After spawning in­ bination of both (Helm et al., 2004; Aji, 2011). Furthermore, physical duction trails, broodstock were held in a 7600 L cylindrical tank within removal of gametes from mature oyster gonads, or ‘strip spawning’, is labelled baskets for two weeks to assess survival before being returned to commonly employed when a high degree of fertilisation control is the holding ponds. required, such as that required in selective breeding programs (Utting Pervious work on wild S. echinata has documented a gender ratio of and Spencer, 1991; O’Connor et al., 2008). 1:1.4 (female:male) and synchronised reproductive development It has long been documented that the presence of spermatozoa in (Nowland et al., 2019c). Because broodstock are valuable and it is not culture water may trigger spawning in conspecifics, as spermatozoa possible to determine gender or reproductive condition without sacri­ contain pheromones that cause chemical stimulation (Galtsoff, 1938, ficinganimals, the exact gender ratio and reproductive condition of the 1940). These pheromones