This article was downloaded by: [203.109.163.22] On: 10 March 2015, At: 18:58 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK Invertebrate Reproduction & Development Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/tinv20 Spatial variation in reproduction in southern populations of the New Zealand bivalve Paphies ventricosa (Veneroida: Mesodesmatidae) Kendall Gadomskia & Miles Lamarea a Department of Marine Science, University of Otago, PO Box 56, Dunedin 9054, New Zealand Published online: 13 Feb 2015. Click for updates To cite this article: Kendall Gadomski & Miles Lamare (2015): Spatial variation in reproduction in southern populations of the New Zealand bivalve Paphies ventricosa (Veneroida: Mesodesmatidae), Invertebrate Reproduction & Development, DOI: 10.1080/07924259.2015.1007216 To link to this article: http://dx.doi.org/10.1080/07924259.2015.1007216 PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. 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Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions Invertebrate Reproduction & Development, 2015 http://dx.doi.org/10.1080/07924259.2015.1007216 Spatial variation in reproduction in southern populations of the New Zealand bivalve Paphies ventricosa (Veneroida: Mesodesmatidae) Kendall Gadomski and Miles Lamare* Department of Marine Science, University of Otago, PO Box 56, Dunedin 9054, New Zealand (Received 25 November 2014; accepted 9 January 2015) Paphies ventricosa is a large surf clam endemic to New Zealand, and whose populations have substantially declined dur- ing the past century owing to overfishing and habitat degradation. Poor recruitment is now evident, and therefore, under- standing the reproductive patterns of P. ventricosa is a key to developing and implementing conservation strategies for the species. This study examines the reproductive cycle of P. ventricosa over one year in a population at Oreti Beach, Southland, the southernmost known extent of the species. At the same beach, we quantify spatial variation in reproduc- tion among four sites using quarterly surveys. Reproductive status is quantified from body indices and histological exam- ination of gonads. Based on changes in oocyte sizes, gametogenic stages and condition index, we observed a species with a primary spawning in spring and a second spawning event in autumn, with no resting phase but minimal reproduc- tive activity over winter. Seasonal reproduction corresponded with warmer sea surface temperature and a peak in chloro- phyll-a concentrations in the region. Small-scale (<15 km) variation in the timing of spawning was also evident along Oreti Beach, and these patterns maybe an important consideration when identifying areas that may be considered for conserving source populations. Keywords: gametogenesis; surf clam; condition index; histology; sea temperature Introduction substantial overfishing in the first half of the twentieth Paphies ventricosa (Veneroida: Mesodesmatidae) Gray century (Rapson 1954), habitat degradation (Beentjes fi 1843, known by the Māori name toheroa, is a large surf et al. 2006) and disturbance from beach traf c are con- clam (up to 150 mm shell length) endemic to New Zealand. tributors (Brunton 1978; Williams et al. 2013). fi The species has a broad latitudinal distribution ranging Recruitment has been identi ed as a key issue for the between 34.5° and 46.3°S, although only three substantial species (Beentjes et al. 2006; Morrison & Parkinson populations now exist, these being physically separated by 2008), and the production and supply of P. ventricosa up to 700 km (Beentjes et al. 2006). The species is larvae may be limited due to the small and fragmented restricted to high-energy dissipating beaches that are on nature of present-day populations. A key aspect in under- western-facing fully exposed coasts made of fine sand standing recruitment in bivalves is quantifying processes (~0.25 mm average grain size) (Rapson 1952;Cassie controlling larval supply, which includes a detailed Downloaded by [203.109.163.22] at 18:58 10 March 2015 1955). Adult size classes (>90 mm) are concentrated at understanding of the spatial and temporal patterns in mid-tide levels, sub-adults (40–90 mm) are higher on the reproductive cycles and gamete production. beach, whilst the juveniles (<40 mm) have a wider and Reproduction has been examined in a range of more even vertical distribution across the tidal range but are temperate bivalve orders such as Veneroida (Newell & most abundant higher up the beach (Beentjes et al. 2006; Bayne 1980; Harvey & Vincent 1989; Gaspar et al. Beentjes & Gilbert 2006). 1999), Mytiloida (Wilson & Hodgkin 1967), Ostreoida P. ventricosa population sizes throughout New (Ruiz et al. 1992), and Myoida (Zaidman et al. 2012). Zealand have decreased substantially over the past cen- This includes a number of bivalve species inhabiting tury. For example, Greenway (1972) estimated that the New Zealand soft sand environments, such as Ruditapes northern population has declined from an estimate of largillierti (Gribben et al. 2001), Panopea zelandica 10,000,000 individuals in 1964 to 1,000,000 in 1971. (Gribben et al. 2004) and Zenatia acinaces (Gribben Southern populations have also experienced similar 2005). For the New Zealand species, reproduction fi declines, with Beentjes et al. (2006) reporting population follows relatively well-de ned annual cycles with spawn- sizes reduced from 2.2 million in the mid-1970s to ing occurring within the spring and summer period. 78,000 individuals larger than 100 mm by 1990. The Of interest in this study is the family Mesodesmati- reasons for the decline are poorly understood, but dae (Bivalvia: Veneroida), in which the reproduction has *Corresponding author. Email: [email protected] © 2015 Taylor & Francis 2 K. Gadomski and M. Lamare been described in a small number of species including threatened bivalve species such as P. ventricosa, where the Australian Donacilla cuneata (Roberts 1984), Asian knowledge of spatial and temporal patterns of reproduc- Coecella chinensis (Kim et al. 2013), the South tion can be used in conservation strategies to maximise American Mesodesma donacium (Peredo et al. 1987; future recruitment by identifying larval source popula- Riascos et al. 2009; Uribe et al. 2012) and Mesodesma tions (Gaines et al. 2010). mactroides (Herrmann et al. 2009), and the tropical spe- cies Atactodea striata (Baron 1992). Reproduction in New Zealand mesodematids, all in the genus Paphies, Materials and methods has been described for P. ventricosa (Redfearn 1974), Study site and animal collection P. australis (Hooker & Creese 1995), Paphies donacina Reproduction in P. ventricosa was examined at four sites (Marsden 1999) and Paphies subtriangulata (Grant & along Oreti Beach, Southland, New Zealand. Oreti Beach Creese 1995). is a south-west facing, 26 km long, dissipating surf Most of what it known about P. ventricosa reproduc- beach on the shores of Foveaux Strait (Figure 1). Each tion comes from the North Island. Hoby (1933) found end of the beach is bordered by two river/estuary sys- – μ that egg diameter increased from June (59 65 m) to tems. – μ October (75 80 m) and that sperm activity increased To examine reproduction over one year, 20 mature “ ” “ from fairly active at the end of July to extremely animals were collected from a single site (Site B) every ” active in October. Additionally, Hoby (1933) found that month between January 2011 and December 2011, at the beginning of October few animals had spawned, excluding April 2011 (Figure 1). The following year but by the end of the month, most animals had spawned. (2012), spatial and seasonal patterns of reproduction in fi Redfearn (1974) identi ed four stages of gametogenic P. ventricosa along Oreti Beach was examined at four fi development in P. ventricosa, classi ed as early active sample sites along the length of the beach (Site A–D) (EA), late active (LA), mature and partially spawned/ for autumn (March), winter (June), spring (September) spent. The study found two to three spawning events and summer (December) (Figure 1). For this, 20 animals occurred during the summer season, with an initial were collected per site per season. All animals collected maturing period