Latitudinal and Cross-Shelf Patterns of Size, Age, Growth, and Mortality of a Tropical Damselfish Acanthochromis polyacanthus on the Great Barrier Reef

Abstract

Patterns of age and growth of a sedentary damsel fish Acanthochromis polyacanthus were tested over a latitudinal range of approximately 10 degrees (1200 km) on the Great Barrier Reef (GBR), Australia. Within latitudes, these patterns were also compared on reefs in distance strata (inner, mid, and outer) across a continental shelf that ranged in width from 52 to 128 km. Although variation in length-max (SLMAX), growth, age-max (AMAX), and the von Bertalanffy metrics of Linf and K were found within and among latitudes, the greatest variation in some demographic characteristics was found among distance strata across the shelf regardless of latitude. Fish were always relatively smaller at inner shelf reefs and grew more slowly when compared to mid and outer shelf reefs; this was true regardless of the color morph of fish. The oldest fish collected was 11 years old, and there was no consistent variation in age-max among distances from shore. On outer reefs, there was a negative linear relationship with age-max and latitude. This “tropical gradient” of age only explained 34% of the variation; furthermore, this was not found when only the oldest group of fish was considered (top 10%). Fish only reached an age-max of six years on the southernmost reefs. There was a trend for a smaller Linf with latitude but it was not significant and Linf did not vary predictably with water temperature. The sampling of marine protected areas (MPAs) and fished zones did not confound the resultant patterns in that fish were not consistently larger or older in MPAs or fished zones. Instantaneous mortality rates were 0.245–0.685; they were highest at inner reefs and also showed no consistent MPA-related patterns. Our study suggested that the mid and outer shelf waters of the GBR appeared best suited for growth of A. polyacanthus. In conclusion, the position on continental shelves dominated other geographical patterns and needs to be considered in spatial models of growth. We suggest that local environmental conditions such as turbidity and the quality and quantity of plankton likely have a strong influence on distance across the shelf-based demographic patterns of planktivores.

Synchronous biological feedbacks in parrotfishes associated with pantropical coral bleaching

“…Recent climate histories are driving synchronous biological and physical patterns across multiple ecosystems (e.g., Black et al, ). The patchiness and high level of demographic diversity across small areas within coral reef systems (Gust, Choat, & Ackerman, ; Kingsford, Welch, & O'Callaghan, ; Taylor, Brandl, et al, ) imply that population dynamics of organisms within coral reefs are heavily influenced by individual microhabitats, perhaps to an extent greater than most other ecosystems. Hence, the temporal synchronization of growth responses across spatially disjunct populations spanning two ocean basins following pantropical bleaching highlights the severity and pervasiveness of the effects of contemporary climate change.…”

Regional versus latitudinal variation in the life‐history traits and demographic rates of a reef fish, Centropyge bispinosa, in the Coral Sea and Great Barrier Reef Marine Parks, Australia

“…It is possible that the sampling design of the present study, spanning 13° of latitude and 2.6°C of mean temperature, was too narrow to identify reaction norms of the TSR that typically span ranges ≥10°C (see Atkinson, 1994 and references therein). However, we note numerous studies on poikilotherms performed across similar thermal gradients of latitude demonstrate both support and contradictions to the predictions of the TSR, depending on the study species (Kingsford et al ., 2019; Ruttenberg et al ., 2005; Trip et al ., 2014). While studies on a single species cannot alone validate or invalidate broad ecological theories, results can add support and help identify deviations to bolster or revise models (Price et al ., 2012).…”

“…Length is often decoupled from longevity in reef fishes, particularly in species with determinate growth patterns, such as C. bispinosa (Berumen et al ., 2012; Kingsford et al ., 2019; Taylor et al ., 2019; Trip et al ., 2008). Notably, Centropyge live in harems with a strict size‐based social hierarchy, where sex change and growth is socially suppressed in subordinates (Aldenhoven, 1984; Allen et al ., 1998; Ang & Manica, 2010a, 2010b; Lutnesky, 1996; Moyer & Nakazono, 1978).…”

“…Moreover, Kingsford et al . (2019) found that the greatest life‐history trait variation of a tropical damselfish Acanthochromis polyacanthus (F: Pomacentridae) occurred across the continental shelf rather than across 10° of latitude within the GBRMP. In this case, A. polyacanthus on inner‐shelf reefs grew slower and achieved a smaller asymptotic length than those on outer‐shelf reefs of the GBRMP (Kingsford et al ., 2019).…”

“…(2019) found that the greatest life‐history trait variation of a tropical damselfish Acanthochromis polyacanthus (F: Pomacentridae) occurred across the continental shelf rather than across 10° of latitude within the GBRMP. In this case, A. polyacanthus on inner‐shelf reefs grew slower and achieved a smaller asymptotic length than those on outer‐shelf reefs of the GBRMP (Kingsford et al ., 2019). Studies have also suggested that Centropyge are found at greater densities in areas of high current speed and upwelling, which may increase the availability and/or quality of dietary resources for C. bispinosa (Eagle et al ., 2001; Moyer & Nakazono, 1978).…”