Spatial variation in the effects of size and age on reproductive dynamics of common coral trout Plectropomus leopardus

Abstract

The effects of size and age on reproductive dynamics of common coral trout Plectropomus leopardus populations were compared between coral reefs open or closed (no-take marine reserves) to fishing and among four geographic regions of the Great Barrier Reef (GBR), Australia. The specific reproductive metrics investigated were the sex ratio, the proportion of vitellogenic females and the spawning fraction of local populations. Sex ratios became increasingly male biased with length and age, as expected for a protogyne, but were more male biased in southern regions of the GBR (Mackay and Storm Cay) than in northern regions (Lizard Island and Townsville) across all lengths and ages. The proportion of vitellogenic females also increased with length and age. Female P. leopardus were capable of daily spawning during the spawning season, but on average spawned every 4·3 days. Mature females spawned most frequently on Townsville reserve reefs (every 2·3 days) and Lizard Island fished reefs (every 3·2 days). Females on Mackay reefs open to fishing showed no evidence of spawning over 4 years of sampling, while females on reserve reefs spawned only once every 2-3 months. No effect of length on spawning frequency was detected. Spawning frequency increased with age on Lizard Island fished reefs, declined with age on Storm Cay fished reefs, and declined with age on reserve reefs in all regions. It is hypothesized that the variation in P. leopardus sex ratios and spawning frequency among GBR regions is primarily driven by water temperature, while no-take management zones influence spawning frequency depending on the region in which the reserve is located. Male bias and lack of spawning activity on southern GBR, where densities of adult P. leopardus are highest, suggest that recruits may be supplied from central or northern GBR. Significant regional variation in reproductive traits suggests that a regional approach to management of P. leopardus is appropriate and highlights the need for considering spatial variation in reproduction where reserves are used as fishery or conservation management tools.

Marine reserves stabilize fish populations and fisheries yields in disturbed coral reef systems

“…, ), adult movement (Zeller and Russ ), reproductive biology (Carter et al. , b), habitat use (Kingsford , Wen et al. ), and larval dispersal (Harrison et al.…”

“…They share a number of life-history characteristics with other exploited reef fishes: they are relatively long-lived with asymptotic growth (Mapstone et al 2004), are protogynous hermaphrodites (Samoilys 2002), and have relatively sedentary reef-associated adult populations connected through dispersing larvae (Zeller and Russ 1998, Harrison et al 2012). There has been considerable research into coral trout demography (Mapstone et al 2004), life-history characteristics (Ferreira and Russ 1994, 2004, adult movement (Zeller and Russ 1998), reproductive biology (Carter et al 2014a, b), habitat use (Kingsford 2008, Wen et al 2013, and larval dispersal (Harrison et al 2012) on the GBR, which provide demographic and dispersal parameter estimates for use in models.…”

Variations in growth, longevity and natural mortality for the protogynous hermaphroditic eightbar grouper Hyporthodus octofasciatus between the Indian and Pacific Oceans

“…This is particularly relevant for species that exhibit pan-oceanic mixing (e.g., Sedberry et al, 1996;Ball et al, 2000), span significant latitudinal, longitudinal and temperature ranges (Wakefield, 2006;Williams et al, 2012a;Cappo et al, 2013;Carter et al, 2014), and/or exhibit spawning omission over a large part of their geographic range (Wakefield et al, 2013b). It is also important that such studies adopt standardised procedures (e.g., methods and interpretations of age estimation from otolith sections) in order to facilitate effective comparisons (see Williams et al, 2012b;Newman et al, 2015).…”

Size and spacing rules can balance conservation and fishery management objectives for marine protected areas

“…When the fishery is better protected, there is a trade‐off in rules reflecting theoretical expectations (Gaines et al., ; Hastings & Botsford, ; Kaplan & Botsford, ). Therefore, if knowledge about connectivity can be used to identify and target important regions for protection, it may be beneficial to cluster protection in key areas, creating fewer, larger MPAs (Carter et al., ; Mace & Morgan, ).…”

“…MPAs (Carter et al, 2014;Mace & Morgan, 2006). Finally, our model illustrates how heterogeneity in reef location and dispersal patterns creates variation in management outcomes among alternate MPA networks.…”