Global human footprint on the linkage between biodiversity and ecosystem functioning in reef fishes

Copyright: © 2011 Mora et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Difficulties in scaling up theoretical and experimental results have raised controversy over the consequences of biodiversity loss for the functioning of natural ecosystems. Using a global survey of reef fish assemblages, we show that in contrast to previous theoretical and experimental studies, ecosystem functioning (as measured by standing biomass) scales in a non-saturating manner with biodiversity (as measured by species and functional richness) in this ecosystem. Our field study also shows a significant and negative interaction between human population density and biodiversity on ecosystem functioning (i.e., for the same human density there were larger reductions in standing biomass at more diverse reefs). Human effects were found to be related to fishing, coastal development, and land use stressors, and currently affect over 75% of the world's coral reefs. Our results indicate that the consequences of biodiversity loss in coral reefs have been considerably underestimated based on existing knowledge and that reef fish assemblages, particularly the most diverse, are greatly vulnerable to the expansion and intensity of anthropogenic stressors in coastal areas

Coral farming as means of sustaining livelihoods and promoting resource management

With the ongoing transition between the barter and the cash economy in Papua New Guinea (PNG), traditional resource production and exploitation must adapt to the changing markets. The increasing demands for goods and services have resulted in coastal and marine resources in PNG showing signs of overexploitation. Andra Island in Manus Province is one of many islands whose inhabitants are highly dependent on the sea for sustenance and livelihoods. Ecological studies by the Wildlife Conservation Society have revealed that the surrounding reefs are denuded of branching Acropora corals compared with similar sites in Manus and elsewhere. This is likely to be due to the island’s economic dependence on the harvest of Acropora corals for the coral lime trade. Lime (calcium hydroxide) is chewed with betelnut (Areca catechu) throughout most coastal regions of PNG, and Andra has a monopoly on the lime trade in Manus. A coral farming project was implemented with the aim of providing a sustainable means of maintaining the coral lime trade. Unlike other coral farming projects in the Pacific, this project operates completely at the local scale and is not reliant on overseas markets; nor does it face the logistical challenges of the aquarium trade. We assess here the degree to which the coral farming activities contribute to livelihoods while relieving extractive pressure on reefs. The project has potential to expand throughout other regions of PNG where corals are harvested for lime

R² values of linear regression analysis of flight initiation distance with body size (cm TL) and group size reported by family and fishing ground.

a<p>*** = <i>p</i><0.001; ** = <i>p</i><0.01 and; * = <i>p</i><0.05.</p

Pre-flight behavior of six reef fish families across four fishing grounds with different fishing pressures.

<p>Occurrence (%) of pre-flight behavioral categories in: (a) Acanthuridae; (b) Scaridae; (c) Balistidae; (d) Lutjanidae; (e) Mullidae; and (f) Serranidae across four reef areas in Papua New Guinea. Darkest shading indicates no notice behavior, followed by tacking away, orientating towards refuge, watching, and inspecting as shading becomes lighter.</p

Mean flight initiation distance (FID) (cm ± S.E) at each fishing ground for six coral reef fish families.

<p>FID was estimated for individuals of six families of coral reef fishes at four different fishing pressures. From left to right within each family, bars are: Kavulik no-take area (no fishing); Ungakum (low fishing pressure); Nusa (intermediate fishing pressure); and Mongol (high fishing pressure). If significant differences existed in FID within families at different fishing grounds, grounds were grouped by similarity (a, b and c). Dashed line is maximum distance at which rifle-style spear guns used in New Ireland province are considered effective (approximately 310 cm, Feary et al. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0022761#pone.0022761-Feary1" target="_blank">[12]</a>).</p

Analysis of covariance (ANCOVA) results of flight initiation distance (cm) with fishing pressure as a fixed factor and fish body size (cm TL) and group size as co-variates.

a<p>*** = <i>p</i><0.001; ** = <i>p</i><0.01 and; * = <i>p</i><0.05.</p

Effect of body size (cm TL) on flight initiation distance (cm).

<p>Flight initiation distance plotted against fish body size for: (a) Acanthuridae; (b) Scaridae; (c) Balistidae; (d) Mullidae; and (e) Serranidae. Black circles, open circles, inverted red triangles and upright green triangles represent Kavulik no-take area (no fishing), Ungakum (low fishing pressure), Nusa (intermediate fishing pressure) and Mongol (high fishing pressure) fishing grounds, respectively. Solid lines are significant linear regression across all grounds and dotted lines are 95% confidence intervals. For significance and R² values see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0022761#pone-0022761-t002" target="_blank">Table 2</a>. Note that scales differ on both X and Y axes.</p

Fear of fishers: human predation explains behavioral changes in coral reef fishes

Prey flight decisions in response to predation risk are increasingly being considered in conservation and management decisions in the terrestrial realm, but are rarely considered in marine systems. This field-based study investigated how the behavioral response of coral reef fish families varied along a gradient of subsistence fishing pressure in Papua New Guinea. Specifically, we examined how fishing pressure was related to pre-flight behavior and flight initiation distance (FID), and whether FID was influenced by body size (centimeters total length), group size (including both con- and hetero-specific individuals), or life-history phase. Fishing pressure was positively associated with higher FID, but only in families that were primarily targeted by spear guns. Among these families, there were variable responses in FID; some families showed increased FID monotonically with fishing pressure, while others showed increased FID only at the highest levels of fishing pressure. Body size was more significant in varying FID at higher levels of fishing pressure. Although family level differences in pre-flight behavior were reported, such behavior showed low concordance with fishing pressure. FID shows promise as a tool by which compliance and effectiveness of management of reef fisheries can be assessed