Grouper and Napoleon Wrasse ecology in Laamu Atoll, Republic of Maldives: Part 2. Timing, location, and characteristics of spawning aggregations

Abstract

The reproductive ecology of five species of grouper and the Napoleon wrasse was studied March-June, 1998 in Laamu Atoll, Republic of Maldives. Research focused on identifying the timing, location, and characteristics of spawning aggregations in this atoll.Timed surveys were used to assess fish abundance and size distribution in Mundoo Channel, which is one of seven channels connecting Laamu Atoll's inner atoll lagoon to the open ocean. Through a pilot study, and later confirmed in the main study, it was concluded that observations could be conducted and compared over different times of the day, tidal cycles, current speeds, and among observers.A spawning aggregation of Plectropomus areolatus, defined as a three-fold abundance increase over ambient levels, was recorded in Mundoo Channel during the new moon in April, 1998. Data collected during the pilot study suggested that an aggregation occurred in this channel during March, 1998. Courtship behavior for this species was recorded during these two months. Data suggested that P. laevis spawned during this time period as well. Spawning was never observed, but abundance increases and courtship behavior indicate that spawning occurred during this time.

Aggregation and spawning of the humphead wrasse Cheilinus undulatus (Pisces: Labridae): general aspects of spawning behaviour

“…Some of the spawning signs indicated may have little to do with reproduction. Sluka (2000) implied that spawning aggregations occur in C. undulatus in the Maldives without any data, repeating the belief of R. E. Johannes & L. Squire (unpubl. data) that C. undulatus aggregates to spawn ‘in large numbers at sites that appear to be similar to sites where grouper aggregate’.…”

“…They indicated, based on observations of others, the aggregation season of C. undulatus in New Caledonia to run from December to March and April and for aggregations to occur on the ‘outer barrier reef near passages'. There are unconfirmed reports of aggregation by C. undulatus (Sluka, 2000; R. E. Johannes & L. Squire, unpubl. data; J.…”

A Decade of Monitoring an Indo-Pacific Grouper Spawning Aggregation: Benefits of Protection and Importance of Survey Design

“…Geographically, the overall pattern of annual spawning season length among species was similar to Palau; generally longest for P. areolatus (at 4-6 months, occasionally more), shortest for E. polyphekadion (1 or 2 months) and intermediate for E. fuscoguttatus (2-4 months) (Rhodes and Sadovy, 2002;Rhodes and Tupper, 2008;Robinson et al, 2008;Rhodes et al, 2011Rhodes et al, , 2014Hamilton et al, 2012;Bijoux et al, 2013;Samoilys et al, 2014;Waldie et al, 2016;Hughes et al, 2020). In terms of seasonality, aggregation for spawning from the Seychelles to the central Pacific cover all months of the year, although January to August are most commonly reported in the published literature (Passfield, 1996;Sluka, 2000;Rhodes and Sadovy, 2002;Pet et al, 2005;Robinson et al, 2008;Hamilton et al, 2011;Wilson et al, 2011;Bijoux et al, 2013;Rhodes et al, 2014;Samoilys et al, 2014;Mourier et al, 2016;Karkarey et al, 2017;Hughes et al, 2020).…”

“…In these studies, the areas sub-sampled were usually where fish were most highly concentrated, usually referred to as 'core' areas, with boundary areas and one or more depth ranges sometimes also included. UVC aggregation surveys typically employed standard transect designs used for general reef fish surveys, ranging from 50 to 250 m in length and with varying swath widths of 4-30 m. Other techniques such as timed swims, radial surveys, photos or phototransects have also been used to study grouper aggregations (e.g., Sluka, 2000;Whaylen et al, 2007;Bijoux et al, 2013;Mourier et al, 2019). Typically, the stated or implicit assumption in such studies was that sub-areas/samples represent the entire aggregation and that fish numbers/densities from these sub-samples are sufficient to define aggregation status or changes over time.…”

Age-based demography of humpback grouper Cromileptes altivelis: implications for fisheries management and conservation

“…Spawning behaviour has been reported for a number of serranid species (e.g. Sadovy et al 1994, Coleman et al 1996, Samoilys 1997, Sluka 2001, Whaylen et al 2004, Matos-Caraballo et al 2006), but C. altivelis spawning in the wild has not been documented (Morris et al 2000). Spawning has been observed in captivity at Indonesian aquaculture facilities, where it occurred throughout most of the year (Mous 2000, Sugama et al 2003), but these observations are from 1 equatorial location and are likely to be strongly influenced by culture conditions.…”