Parrotfish

Caribbean parrotfish foraging: An interspecific comparison of algal preferences

In recent decades, reduced grazing pressure caused by a die-off of Diadema antillarum and the overexploitation of herbivorous fishes have facilitated a phase shift from coral to algal dominated reefs. Thus, conservation of herbivorous fishes has become increasingly important on coral reefs. In the Caribbean reefs, parrotfish are the dominant herbivores. Studies have been conducted on parrotfish grazing, but there is a lack of knowledge about specific algal preferences. This study examined differences in bite frequencies on algal types and algal preferences of the most common parrotfish species of Bonaire, Dutch Caribbean. Mean bite frequencies (bites 30 min-1 ) and preferences were determined by offering algal plates with Padina sp., Ulva sp., Sargassum sp., and turf algae to parrotfish on the coral reef flat. During field observations, data was collected on the number of bites taken and algal type grazed by each individual parrotfish. Parrotfish as a group, and individual species (Sparisoma rubripinne, Scarus viride, and Sparisoma aurofrenatum), demonstrated significant differences in mean bite frequencies on algal types offered. There were also significant differences in mean bite frequencies among the three parrotfish species. All species of parrotfish, collectively and individually, demonstrated preferences for Padina sp. and avoidances for all other algal types offered. Determining which algal types parrotfish graze, and how grazing differs among parrotfish species is ecologically important. The results provide an understanding of how the selective pressures of specific herbivores may help regulate harmful macroalgae, and suggest the importance of maintaining the diversity of herbivorous fishes on the reef.

This student research was retrieved from Physis: Journal of Marine Science XIV (Fall 2013)19: 110-117 from CIEE Bonaire.

Date
2013
Data type
Other resources
Theme
Research and monitoring
Geographic location
Bonaire
Author

Influence of habitat on defecation behavior of queen (Scarus vetula) and princess (Scarus taeniopterus) parrotfish

Herbivores are important structuring agents for ecosystems worldwide. While effects of grazing by herbivorous fish are well studied, their roles in organismal dispersal have only recently become a topic of interest. Location preference and range of defecation may indicate the importance of their contribution to organism spreading. This study therefore examined the distribution and frequency of defecation of the princess parrotfish (Scarus taeniopterus) and queen parrotfish (Scarus vetula) between coral reef and sand flat habitats. Observations were performed using SCUBA in Bonaire, Dutch Caribbean. Target species were observed for 20-minute trials in each habitat. Defecation frequency, bite frequency, maximum distance between defecations, and location of defecation were recorded and averaged for each species in each habitat, and compared between species and habitats through two-way analysis of variance (ANOVA). Additionally, unique food sources observed during trials were sampled and examined in the lab. S. taeniopterus individuals were found to defecate significantly less and have smaller maximum distance between defecations within the reef habitat than the sand habitat, while S. vetula did not show significant behavioral changes for any of the variables between the two habitats. Lab results also suggest that S. taeniopterus may be opportunistic omnivores. This study offers insight to behavioral plasticity and specificity to habitat type, and provides a broader understanding of dietary plasticity and ecological roles for S. taeniopterus and S. vetula.

This student research was retrieved from Physis: Journal of Marine Science XIV (Fall 2013)19: 1-13 from CIEE Bonaire.

Date
2013
Data type
Other resources
Theme
Research and monitoring
Geographic location
Bonaire
Author

Status and Trends of Bonaire’s Reefs, 2011. Cause for grave concerns

Unusually warm ocean temperatures surrounding Bonaire during the late summer and fall of 2010 caused 10 to 20 % of corals to bleach (Fig. 1). Bleaching persisted long enough to kill about 10 % of the corals within six months of the event (Steneck, Phillips and Jekielek Chapters 2A – C). That mortality event resulted in the first significant decline in live coral at sites monitored since 1999 (Fig. 2). Live coral declined from a consistent average of 48 % (from 1999 to 2009) to 38 % in 2011 (Steneck Chapter 1). This increase in non-coral substrate increased the area algae can colonize and the area parrotfish must keep cropped short (Mumby and Steneck 2008). For there to be no change in seaweed abundance would require herbivorous fish biomass and population densities to increase, but they have been steadily declining in recent years. This decline in parrotfish continues despite the establishment of no-take areas (called Fish Protection Areas – FPAs) and the recent law that completely bans the harvesting of parrotfish. The other major herbivore throughout the Caribbean is the black spined sea urchin, Diadema antillarum. However, since 2005 Diadema abundance has steadily declined. Damselfishes continue to increase in abundance (except in FPAs) and their aggressive territoriality reduces herbivory where they are present. These declines in herbivory resulted in a marked increase in macroalgae (Steneck Chapter 1). Although patchily distributed, algae on some of Bonaire’s reefs are approaching the Caribbean average (Kramer 2003). All research to date indicates that coral health and recruitment declines directly with increases in algal abundance (e.g., Arnold et al 2010).
On the bright side, predatory fishes are increasing in abundance in general but increasing most strongly in FPAs. Typically, responses to closed areas take 3 - 5 years to begin to manifest themselves. Predators of damselfishes have increased significantly in FPA sites and there, damselfish abundances are trending downward. These trends are the first signs of changes in the FPAs, and they are encouraging.
Overall, Bonaire’s coral reefs today are more seriously threatened with collapse than at any time since monitoring began in 1999.
 
Monitoring Results
The abundance of live coral at the monitoring sites has been remarkably constant since 1999. However, the bleaching related mortality event (Fig. 1) resulted in the first marked decline in live coral.
Seaweed abundance (“macroalgae”) increased sharply in 2011. While the greatest increase in algae occurred at the 18th Palm site where effluent could have increased nutrient levels, most of the other sites showed marked increases in algal abundance (see Steneck Chapter 1). Coralline algae, which has been shown to facilitate coral recruitment, remains at or near unprecedentedly low levels (Fig 2). Herbivory from parrotfishes and the grazing sea urchin Diadema antillarum remains at or near the lowest levels recorded since monitoring began in 1999 (Fig. 3 and see Cleaver Chapter 5). Herbivory from parrotfish is widely thought to be most important (e.g., Steneck and Mumby 2008) but territorial damselfishes can negate parrotfishes’ positive effects by attacking grazing herbivores and preventing them from effectively grazing (Arnold et al 2010). Damselfish abundances have trended upward in recent years (Fig. 3). However, there is a hint of a reversal to this trend in the FPAs (see Arnold Chapter 3). This reversal is consistent with the possibility that areas without fishing have elevated abundances of damselfish predators such as species of groupers and snappers (Randall 1965)  
Predatory fishes including snappers, groupers, barracuda, grunts and others increased in abundance at our monitored sites (Fig. 4 and see DeBey Chapter 6a). Specific predators known to eat damselfishes (see Preziosi Chapter 6b) show variable population densities with only a hint of an increase in 2011.   
Predatory fishes increased in abundance in both biomass (most striking) and population densities (Fig. 5). While biomass of predators in FPA and control sites is identical, the population density of predators is slightly greater at FPA sites
Coral recruitment remained lower than recorded in 2003 and 2005 (Fig. 6). However, the abundance of juvenile corals was higher in 2011 than was quantified in 2009

Date
2011
Data type
Research report
Theme
Research and monitoring
Report number
5
Geographic location
Bonaire

A Report on the Status of the Coral Reefs of Bonaire in 2005 with Advice on a Monitoring Program

This report characterizes the state of Bonaire’s reefs as of March 2005. We pay particular attention to structural and functional attributes of reefs that have changed in so many other Caribbean reefs. We characterize coral reefs by their resident organisms and the forces regulating their distribution and abundance. Thus, corals, algae and fish define the “structure” of coral reefs but climate changes, diseases, hurricanes, overfishing, sedimentation and excess nutrients may affect how they “function”. Recent unfavorable changes in the structural and functional attributes of reefs have caused “the coral reef crisis” (Bellwood et al. 2004). In Caribbean coral reefs the most alarming changes have been the declines in the abundance of corals, sea urchins and reef fishes and the accompanying increases in large harmful seaweeds (called “macroalgae”). The decline in coral and increase in macroalgae, called a “phase shift”, represents a significant change in the structure of coral reef ecosystems that could lower its resilience.

...

 

In March of 2005, a team of graduate students from the University of Maine revisited six study reefs on Bonaire to determine the status of those reefs and to detect if any change has occurred since March of 2003 when the last such survey was conducted. The study sites established in 2003 from north to south are: Karpata, Barcadera, Reef Scientifico, Forest on Klein Bonaire, Plaza and Windsock. Bonaire’s shallow (10 m) reefs remain in good condition. Coral cover averaged 47% in 2005 compared to 46% in 2003 (no change). Turf algae have increased and coralline algae have declined slightly over the past two years. Harmful seaweed “macroalgae” abundance remains low (2% in 2005 and 5% in 2003; see Steneck in this report) at the 10 m depth we studied. At depths below 20 m, macroalgae are now and have been (for at least the past 30 years) much more abundant (e.g. Van den Hoek et al. 1975) The absence of macroalgae in Bonaire most likely relates to the abundance of seaweedeating species or “herbivores”. Caribbean-wide, harmful macroalgal seaweed abundance corresponds inversely with the abundance of grazing fish such as parrotfish and tangs (Fig. 1). No comparable plot exists for seaweed abundance and any other measured factor on reefs.

...
Changes over the past two decades
Comparisons between the status of reefs over a few years tell us little about long-term changes. For example, today there is a distinct demarcation between where Bonaire’s fringing reefs begin at 5 to 10 m depth and the shore. This region today is largely coralfree and dominated by rubble and sediment laden turf algae. However, this may not have always been the case. Prior to whiteband disease that killed nearly 90% of the elkhorn and staghorn corals in the Caribbean (i.e. Acropora palmata and A. cervicornis) (Aronson et al. 1998, Aronson and Precht 2001), most of the near shore zone was coral-dominated.
...
Coral cover in the near shore zone surrounding Bonaire has declined dramatically and is now dominated by dead coral rubble where once elkhorn and staghorn corals had formed near monocultures prior to white band disease. Five of our six study sites have changed dramatically over the past 20 years except for Karpata. The decline of the Acropora species may have allowed competitively inferior species such as lettuce, pencil, finger and fire corals (Agaricia spp, Madracis spp, Porites porities and Millepora complanata) to expand since all have increased in abundance since the Van Duyl study (1985). Corals are not the only group to have changed dramatically since the 1980s. Diadema antillarum, the dominant grazing sea urchins was abundant in the near shore zone until it succumbed to the mass mortality of the mid 1980s. Today, more than 20 years later it remains below detectable levels at most of the sites we studied (Smith and Malek this report, Steneck this report). These changes, along with the significant declines in large predator finfish (see Bonaire Report 2003) indicate that several key players for the resilience of coral reefs (e.g. Fig. 3) have declined in abundance.

Date
2005
Data type
Research report
Theme
Research and monitoring
Report number
2
Geographic location
Bonaire

Reducing bycatch in coral reef trap fisheries: escape gaps as a step towards sustainability

Widespread use of minimally selective fish traps has contributed to the overfishing of Caribbean coral reefs. Traps typically target high-value fish such as groupers (Serranidae and Epinephelidae) and snappers (Lutjanidae), but they also have high bycatch of ecologically important herbivores (parrotfish (Scaridae) and surgeonfish (Acanthuridae)) and non-target species. One strategy for reducing this bycatch is to retrofit traps with rectangular escape gaps that allow juveniles and narrow-bodied species to escape; yet the effectiveness of these gaps has not been thoroughly tested. On the shallow reefs of Curaçao, Netherlands Antilles, I compared the catch of traditional Antillean chevron traps (the control) to the catch of traps with short escape gaps (20 × 2.5 cm), traps with tall escape gaps (40 × 2.5 cm), and traps with a panel of large aperture mesh. With data from 190 24-h trap sets, the mean number of fish caught was 11.84 in control traps, 4.88 in short gap traps, 4.43 in tall gap traps, and 0.34 in large mesh traps. Compared to controls, traps with short or tall gaps caught significantly fewer bycatch fish (–74 and –80% respectively), key herbivores (–58 and –50% respectively), and butterflyfish (Chaetodontidae; –90 and –98% respectively). The mean length of captured fish was significantly greater in gap traps because juveniles were able to escape via the gaps. Escape gaps reduce neither the catch of high-value fish, nor the total market value of the catch. Therefore, using escape gaps could make trap fishing more sustainable without reducing fishermen’s revenues.

Date
2010
Data type
Scientific article
Theme
Research and monitoring
Geographic location
Curacao
Author

A Report on the Status of the Coral Reefs of Bonaire in 2007 with Results from Monitoring 2003 – 2007

Bonaire’s reefs remain among the best in the Caribbean. However, our monitoring has revealed some potentially troubling trends that may require management action. In 2005, we reported to the Bonaire Marine National Park on the status of Bonaire’s coral reefs, and we suggested a strategy for monitoring trends among four key reef attributes we believe track the health and resilience of Bonaire’s reefs (Steneck and McClanahan 2005). Here we report the results of monitoring studies conducted 2003, 2005 and now 2007 at each site. Where appropriate, we drew from Bonaire’s first AGRRA assessment conducted in February 1999 (Kramer and Bischof 2003) to extend temporal trends over a period of eight years. 
Troubling trends
We see three troubling trends of increased macroalgae, declining herbivory from parrotfish, and increases in damselfish populations. Of these, the first two are most serious (see Chapters 1, 2 and 3). Secondary trends of concern, increases in damselfish populations (Chapter 4) and declines in coralline algae (Chapter 1), could lead to reduced recruitment of reef corals (Chapter 7), but to date this is not evident (Chapter 7). Importantly, coral cover remains relatively high (Chapter 1). The monitored group of carnivorous fishes, the lutjanid snappers, are holding constant but we remain concerned about the past (Steneck and McClanahan 2003) and continued loss of other larger bodied reef carnivores such as groupers and barracuda. The positive ecological role of parrotfish is well documented (e.g. Mumby et al. 2006) so their decline is troubling. It is unclear exactly why their population densities are declining. While parrotfish are not currently a widely sought group of reef fish (Chapter 8), fishing pressure on them is growing. It is possible they are vulnerable to even modest fishing pressure, particularly from fish traps. Accordingly, we recommend that the capture and killing of parrotfish be stopped because of their key ecological role on Bonaire’s coral reefs. Further, other groups of grazing herbivores such as the longspined sea urchin (Diadema antillarum) are increasing but too slowly to effectively replace the functional role of parrotfish (Chapter 1). We suggest continued monitoring of key drivers of reef health (coral cover, algal abundance, herbivory and coral recruitment). Some standard protocols such as the Atlantic and Gulf Rapid Reef Assessment (AGRRA) are entirely commensurable with the data presented in our reports in 2003, 2005 and 2007 (this report). A streamlined monitoring protocol is likely to be most useful to managers to alert them as a potential problem is growing and, perhaps more importantly, to show improvement when it occurs.
 
 

Date
2007
Data type
Research report
Theme
Research and monitoring
Report number
3
Geographic location
Bonaire

Spatial and demographic consequences of nursery-dependence in reef fishes: an empirical and simulation study

The rainbow parrotfish Scarus guacamaia has an obligate dependence on man- groves at juvenile stages, and, as the largest herbivorous fish in the Caribbean region, its distribution has important implications for coral reefs. The effect of connectivity with mangroves on relative density, biomass and size of S. guacamaia was assessed from over 65 km of visual sur- veys from Bonaire, Caribbean Netherlands. In addition, an individual-based, age-structured, mechanistic model (IBM) was developed to explain dispersal patterns from nurseries for S. guaca- maia. In the IBM, mortality was constant, growth was determined by a von Bertalanffy growth equation, and movement was modeled through a random walk process. Using the IBM, simula- tions were run to generate patterns of density, biomass, and size with distance from nurseries. Rainbow parrotfish were observed as far as 42 km away from the nearest mangroves on Bonaire. Relative density and biomass showed significant exponential declines with distance from the pri- mary mangrove nursery and were significantly higher in high versus low complexity non-man- grove habitats. Mean size increased linearly with distance (r2 = 0.74), reflecting an absence of smaller individuals with greater distance. These results were closely mirrored by the simulation study: density and biomass declined exponentially with distance from nurseries, and size and age increased following saturating functions. The results suggest that mangroves may have the poten- tial to supply individuals much further than previously thought. Both the empirical and simulation studies reaffirm calls to prioritise protection of reef habitats close to nurseries as well as the nurseries themselves. 

Date
2015
Data type
Scientific article
Theme
Research and monitoring
Geographic location
Bonaire

Global assessment of the status of coral reef herbivorous fishes: evidence for fishing effects

Abstract:

On coral reefs, herbivorous fishes consume benthic primary producers and regulate competition between fleshy algae and reef-building corals. Many of these species are also important fishery targets, yet little is known about their global status. Using a large-scale synthesis of peer-reviewed and unpub- lished data, we examine variability in abundance and biomass of herbivorous reef fishes and explore evidence for fishing impacts globally and within regions. We show that biomass is more than twice as high in locations not accessible to fisheries relative to fisheries-accessible locations. Although there are large biogeographic differences in total biomass, the effects of fishing are consistent in nearly all regions. We also show that exposure to fishing alters the structure of the herbivore community by disproportionately reducing bio- mass of large-bodied functional groups (scraper/excavators, browsers, grazer/ detritivores), while increasing biomass and abundance of territorial algal- farming damselfishes (Pomacentridae). The browser functional group that consumes macroalgae and can help to prevent coral–macroalgal phase shifts appears to be most susceptible to fishing. This fishing down the herbivore guild probably alters the effectiveness of these fishes in regulating algal abun- dance on reefs. Finally, data from remote and unfished locations provide important baselines for setting management and conservation targets for this important group of fishes. 

Date
2013
Data type
Scientific article
Theme
Research and monitoring

Activity budget of the princess parrotfish (Scarus taeniopterus): a comparison between daylight and sunset periods

Abstract:

Most animals are active either during the day, night, or twilight, and transition periods between these times exhibit interesting behavior. Actions may be related to avoiding predators, seeking shelter, defending territory, feeding, or other interests. Herbivorous fishes on coral reefs, such as parrotfishes, forage constantly throughout daylight periods due to inefficient feeding and reliance on light. At sunset, parrotfishes seek cover under which to rest at night, to conserve energy and avoid predation. To do so, parrotfish decrease feeding and increasing migration and aggression to do so. This study compared how initial phase (IP) and terminal phase (TP) princess parrotfish (Scarus taeniopterus) allocate time between daylight and sunset periods, specifically regarding time spent feeding and being aggressive. Observations were performed using SCUBA at Yellow Sub dive site on Bonaire, Dutch Caribbean. Individuals of S. taeniopterus were followed for 1 min (to allow for acclimatization), followed by 5 min of behavioral observation. Percent time spent on each behavior was calculated and averaged across each category (e.g. IP, daylight), and mean percent time spent feeding and being aggressive were tested using a two- way analysis of variance (ANOVA), with phase and time of day as factors. Both IP and TP fish had a higher mean percent time feeding and a lower mean percent time being aggressive in the morning than at sunset, and time of day and phase were both significant factors affecting variation in both behaviors. The results of this study give insight into the adaptations parrotfish have developed to increase survival. 

Date
2012
Data type
Research report
Theme
Research and monitoring
Geographic location
Bonaire
Author