Man in wetsuit driving small boat on calm day

Dr Mike Emslie

Research Team Leader

Long-Term Monitoring

Contact email

My early research interests focused on reef fish ecology and behaviour, particularly the interface between fishes and their habitat. Upon joining the Long-Term Monitoring Program (LTMP) in 2004, my research focus shifted to quantifying the spatio-temporal patterns of distribution, abundance and diversity of reef fishes, how disturbances shape and influence reef fish assemblages and the effectiveness of management zoning on coral reefs of the Great Barrier Reef (GBR). The LTMP also reports on the condition and trends of GBR coral reefs and provides robust scientific information to managers and policy makers.

PhD, James Cook University
Bachelor of Science Hons., James Cook University, Townsville AU

Status and trend of GBR reefs

Information from LTMP has been instrumental in apprising the Great Barrier Reef Marine Park Authority (GBRMPA), government and stakeholders on the status of the GBR and uses web-based reporting products to ensure timely dissemination of information upon completion of each survey cruise. Upon completion of each field season, an online annual update on the status of the GBR is produced, along with substantial media exposure.

LTMP data also feeds directly into the five yearly GBR Outlook Report produced by the GBRMPA under the auspices of the Australian Governments Reef 2050 Sustainability Plan.

Spatio-Temporal patterns in reef fishes

One of the fundamental goals in ecology is to understand how populations and communities are distributed and structured. Such information is crucial for management, conservation and determining how coral reefs are altered in response to anthropogenic and natural stressors. Data from the LTMP enabled an assessment of the fundamental distribution and abundance patterns of coral and reef fish assemblages across the majority of the GBR province. The most consistent spatial pattern in GBR reef fishes from LTMP data was a partitioning of the assemblage structure across the continental shelf. There have been distinct inshore, mid-shelf and outer-shelf assemblages identified for all groups of fishes examined

Effects of zoning

Evidence for beneficial effects of the initial zoning plan of the Great Barrier Reef Marine Park (GBRMP)1983-2004) was not universal and the expansion of the area of No-Take Marine Reserves (NTMRs) following the 2004 re-zoning of the Park was a bold social and political move that was highly controversial. Thus, it was important to demonstrate tangible benefits of the move. A collaboration with colleagues from James Cook University revealed rapid and significant increase in the density, length and biomass of coral trout in NTMRs compared to reefs that remained open to fishing, and these effects persist to this day. A later study also demonstrated that NTMRs can increase the resilience of coral reef assemblages to natural disturbance regimes.

Disturbance and recovery of coral and fish assemblages

Disturbances play a fundamental role in structuring many ecological communities. Data from the LTMP has provided pivotal information on the effects of disturbance regimes on the status and health of the GBR. A series of papers revealed that sub-regional trends in hard coral cover were diverse, with some being very dynamic while others changed very little, and that disturbances have differential effects on benthic assemblages of coral reefs, particularly hard corals. Habitat complexity has been shown to be an important driver of reef fish assemblage structure and the largest declines in the abundance and diversity of reef fishes occurred on reefs where both coral cover and complexity has been reduced. An examination of recovery dynamics revealed that hard coral cover on reefs in two disparate areas of the GBR recovered at similar rates, however differences in the underlying reef matrix rugosity was influential in how the recovery of associated fish assemblages progressed.

Herbivorous fishes

The replacement of corals by macroalgae is globally considered a sign of reef degradation. An understanding of the mechanisms that drive and sustain such phase shifts is relevant to reef managers, and the LTMP data have been applied to this field in different ways. In 2010 the LTMP reported that an ongoing 7-year phase shift at an inshore reef was strongly associated with a depauperate herbivorous fish community: particularly related to low general diversity and very low abundances of two functional groups. Another study found that the phase shift threat based on herbivore functionality varied throughout the GBR, being strongest on turbid inshore reefs, and that certain environmental factors could act in concert to lower or raise resilience thresholds.


Cheal AJ, Emslie MJ, Currey-Randall LM, Heupel MR. (2021) Comparability and complementarity of reef fish measures from underwater visual census (UVC) and baited remote underwater video stations (BRUVS). Journal of Environmental Management. 289:112375.

Cheal AJ, Emslie MJ. (2020) Counts of coral reef fishes by an experienced observer are not biased by the number of target species. Journal of Fish Biology. 97(4):1063-71.

Madin EM, Madin JS, Harmer AM, Barrett NS, Booth DJ, Caley MJ, Cheal AJ, Edgar GJ, Emslie MJ, Gaines SD, Sweatman HP. (2020) Latitude and protection affect decadal trends in reef trophic structure over a continental scale. Ecology and Evolution. 10(14):6954-66.

Emslie MJ, Bray P, Cheal AJ, Johns KA, Osborne K, Sinclair-Taylor T, Thompson CA. (2020) Decades of monitoring have informed the stewardship and ecological understanding of Australia's Great Barrier Reef. Biological Conservation. 252:108854.

Mellin C, Thompson A, Jonker MJ, Emslie MJ. (2019) Cross-shelf variation in coral community response to disturbance on the Great Barrier Reef. Diversity. 11(3):38.

Emslie MJ, Logan M, Cheal AJ. (2019) The distribution of planktivorous damselfishes (Pomacentridae) on the Great Barrier Reef and the relative influences of habitat and predation. Diversity. 11(3):33.

Johns KA, Emslie MJ, Hoey AS, Osborne K, Jonker MJ, Cheal AJ. (2018) Macroalgal feedbacks and substrate properties maintain a coral reef regime shift. Ecosphere. 9(7):e02349.

Emslie MJ, Cheal AJ, MacNeil MA, Miller IR, Sweatman HP. (2018) Reef fish communities are spooked by scuba surveys and may take hours to recover. PeerJ. 6:e4886.

Cheal AJ, MacNeil MA, Emslie MJ, Sweatman H. (2017) The threat to coral reefs from more intense cyclones under climate change. Global Change Biology. 23(4):1511-24.

Osborne K, Thompson AA, Cheal AJ, Emslie MJ, Johns KA, Jonker MJ, Logan M, Miller IR, Sweatman HP. (2017) Delayed coral recovery in a warming ocean. Global Change Biology. 23(9):3869-81.

Emslie MJ, Cheal AJ, Logan M. (2017) The distribution and abundance of reef-associated predatory fishes on the Great Barrier Reef. Coral Reefs. 36(3):829-46.

Mellin C, Aaron MacNeil M, Cheal AJ, Emslie MJ, Julian Caley M. (2016) Marine protected areas increase resilience among coral reef communities. Ecology Letters. 19(6):629-37.

Emslie MJ, Logan M, Williamson DH, Ayling AM, MacNeil MA, Ceccarelli D, Cheal AJ, Evans RD, Johns KA, Jonker MJ, Miller IR. (2015) Expectations and outcomes of reserve network performance following re-zoning of the Great Barrier Reef Marine Park. Current Biology. 25(8):983-92.

Emslie MJ, Cheal AJ, Johns KA. (2014) Retention of habitat complexity minimizes disassembly of reef fish communities following disturbance: a large-scale natural experiment. PLoS One. 9(8):e105384.