habitat

The genus Alsophis used to be very abundant in the Lesser Antilles. Numbers have declined ascribed to anthropogenic causes and the introduction of invasive species to their habitat. Most Alsophis species are classified as endangered or critically endangered by the IUCN. Alsophis rufiventris, a species native to the islands Saba and St. Eustatius, is facing a constant threat of the Javan mongoose being introduced in its habitat. Also dogs, cats, rats and humans actively influence the abundance of A. rufiventris. Though all these threats, the population of A. rufiventris seemed stable and was classified as vulnerable by the IUCN in 2016. In 2017 hurricane Irma and Maria impacted on Saba and St. Eustatius. It was expected that the A. rufiventris population was altered. Therefore a new population assessment was done in the Quill and Boven National Park on St. Eustatius in 2018 and was repeated in this study. In 2018 the population size in the study area was 165.

Distance sampling with line transects was used to estimate the population size of A. rufiventris. In this study 1068 line transect surveys resulted in 60 snakes recordings. As the snake count was sparse, N-mixture models were used as well.

Distance sampling resulted in a population size of 464 and the N-mixture models resulted in a population size of 178. These results are preliminary, as covariates had no influence on the model in the program DISTANCE. While, according to earlier research by Savit et al. in 2015 the covariates should influence the results. Multipliers have to be added in the program DISTANCE to get more accurate results. From this study the habitat preference of A. rufiventris cannot be described, as the findings on habitat categories were not significantly different from each other.

A. rufiventris is becoming more rare in its native habitat and that is a cause for concern. As many threats to the species are present, but also actively influence their abundance, the species might become, or effectively already can be categorized as (critically) endangered. It is advised to continue monitoring of this species not only on St. Eustatius but on Saba as well. Also conservation actions like establishing biosecurity and conducting rodent control might be beneficial. As these conservation actions might not happen in the near future, a breeding program in a zoo might be beneficial to preserve the genetic variance in the population.

Sea turtles are basically creatures that spend their entire lives in marine or estuarine habitats.Their only remaining reptilian ties to terrestrial habitats are for nesting and restricted cases of basking. Consequently.physiological. anatomical. and behavioral adaptations have evolved largely in response to selection in the aquatic environment and sea turtles share many common elements with liirger tislics and cetaceans in their habitat utilization and migrations. A generalized habitat model may he con- structed for sea turtles based on ontogenetic stages (Figure 6.1):

I. Early juvenile nursery habitat (usually pelagic and oceanic).
2. Later juvenile developmental habitat (usually demersal and neritic).

3. Adult foraging habitat.
4. Adult inter-nesting andfor breeding habitat. 

All sea turtles move immediately to the sea after hatching, usually after dark, and swim actively offshore. Most then undertake a mostly passive, denatant {sensu Jones)' migration drifting pelagically in oceanic gyre systems. Subsequently, after a period of years, these now larger and older juveniles actively recruit to demersal neritic dcvelopmentai habitats in the tropical and temperate zones. Demersal juve- niles in some temperate zone populations make seasonal migrations to foraging areas at higher latitudes in summer and lower latitudes in winter (see below) while those in tropical areas are more localized in their movements, When approaching maturity, pubescent turtles move into adult foraging habitats. In some populations adult habitats are geographically distinct from juvenile developmental habitats;24in others they may overlap or coin~ide.U~p.~on maturity as the nesting season approaches adults make a contranatant migration toward the nesting beaches. Most mating occurs t poorly defined courtship areas that are clone KÃthe nesting beaches relitlive lo the distant foraging areas. Afler mating the females move to their respcclivc nesting beaches.'-* Courtship areas may be directly HITthe nesting beaches,*or remote from the beaches,'" depending on the population. During the nesting season, females usually become resident in the internesting habitat in the vicinity of the nesting beach." The focus of the present paper is habitat utilization and migration of juvenile sea turtles and nursery and developmental habitats. 

Spinyhead blennies (Acanthemblemaria spinosa) and secretary blennies (Acanthemblemaria maria) are abundant, tube-dwelling fishes on the reefs of Bonaire, Netherlands Antilles. In other areas of the Caribbean A. maria are relatively rare and although habitat partitioning has been described for A. spinosa, little is known concerning habitat partitioning in A. maria or about the competitive interactions between the two species. This study determines the species distribution and density of A. spinosa and A. maria in the nearshore reefs of Bonaire and documents the competitive interactions between the 2 species using a manipulative experiment. The distribution of A. spinosa and A. maria was determined using transects on the reef slope and by observations of patch reefs on the reef flat. Experimental condos were constructed and placed on sand flats at 6 m depth, where there is overlap of the ranges. Five individuals from both species were captured and placed on a condo to observe the competitive interactions between A. spinosa and A. maria. A. maria are more abundant on the reef flat while A. spinosa are primarily found on the reef slope (> 6 m). In the condo experiments A. maria were dominant over A. spinosa. It is hypothesized that the slightly larger size and increased competitive nature due to higher densities of A. maria give them an advantage over A. spinosa. This study supports previous findings on the distribution of A. maria and A. spinosa on coral reefs and documents competitive dominance of A. maria over A. spinosa.

This student research was retrieved from Physis: Journal of Marine Science IV (Fall 2008)19: 30-34 from CIEE Bonaire.

Foraging success is affected by choice of feeding association, color phase, and habitat type. Bar jacks (Caranx ruber) exhibit a number of feeding associations, changes in coloration from silver to dark brown/black, and utilize different habitat types within the fringing reef ecosystem for feeding. The objective of this study is to determine if foraging success is affected by 1) feeding association utilized (individual, conspecific, or multispecies groups) 2) color (black or silver) or 3) habitat type (reef flat or reef slope). Observations of C. ruber were conducted at two dive sites on the fringing reef of Bonaire using SCUBA. The number of bites min-1 was used as a measure of foraging success. Analysis of results shows that C. ruber has significantly greater foraging success when feeding alone and in multispecies groups as opposed to feeding with conspecifics. Dark brown/black C. ruber have double the feeding rate as that of silver and habitat type did not have an affect on C. ruber foraging success. In conclusion, foraging success of C. ruber, measured in bites min-1 , is affected by choice of feeding association and coloration, but is not affected by choice of habitat.

This student research was retrieved from Physis: Journal of Marine Science V (Spring 2009)19: 10-13 from CIEE Bonaire.

The spotted moray eel, Gymnothorax moringa, is one of the most abundant moray eels found in the coastal waters of Bonaire, N.A. However, little is known regarding the factors that contribute to its choice of habitat, behavior, and times of activity. Contradictory evidence has been reported for many species of Gymnothorax as to whether they are nocturnal or diurnal, yet little is known concerning color and size, which may be correlated to diet and choice of habitat. This study sought to determine how size, behavior, and color correlate with reef flat and reef slope habitats and at what time (morning or evening) G. moringa is most active. Observations of G. moringa were conducted in the westward coastal waters of Bonaire. A “U”-shaped search pattern was utilized in locating spotted moray eels in 5 adjacent study areas extending perpendicular from the shore to a depth of ~ 15 m. Once an individual was located behavior, jaw size, and color, were recorded in order to assess differences among individuals on differing habitats (reef flat or reef slope), and times of day (morning: 6:00 - 7:30 or evening: 18:00 – 19:30). G. moringa was found to be in greater abundance on the reef flat in the evening displaying exposed venting behavior and individuals were predominantly white in coloration. In the morning G. moringa were found to be in greater densities on the reef slope, displaying foraging behavior, and were predominantly black in coloration. Representatives of all size classes were distributed on the reef flat regardless of time, however, small individuals were not observed on the reef slope in the evening.

This student research was retrieved from Physis: Journal of Marine Science VI (Fall 2009)19: 7-13 from CIEE Bonaire.

Parrotfish are a common and important component of the fringing reefs ecosystem surrounding Bonaire, N.A. In the reef environment, large herbivores like parrotfish graze on macroalgae, allowing for higher coral diversity and abundance. This research studies habitat use among five common species of parrotfish, Scarus guacamaia, Sparisoma viride, Scarus taeniopterus, Sparisoma aurofrenatum, and Scarus vetula found on the leeward coast of Bonaire. The study was performed between Playa Lechi and Something Special dive sites, where transect tapes were placed at three depths representing different habitat types (shallow ridge, reef crest, and reef slope). After a brief recovery period (~ 1 hour), abundances of initial phase and terminal phase parrotfish were determined using SCUBA during midday, and again at night. Parrotfish density was higher during the day than at night and was significantly different among the three depths. Fisher’s PLSD post-hoc test showed that parrotfish density was significantly higher at 12 m than at 1 or 20 m. During the day, density of initial phase parrotfish was significantly higher than terminal phase, but there was no difference among the three depths. At night, there was no difference between the density of initial phase and terminal phase parrotfish, but there were more parrotfish found at 12 m than at 1 or 20 m. Based on the results of this study, more parrotfish are spotted during the day, parrotfish are found most often at 12 m during the night and day, and there are more initial phase parrotfish than terminal phase at all three depths during the day. Overall, significant findings include information about parrotfish habitat and differences between phases, with the additional note that 12 m depth seems to be an important habitat range for parrotfish in Bonaire.

This student research was retrieved from Physis: Journal of Marine Science VI (Fall 2009)19: 1-6 from CIEE Bonaire.

Many fish prefer to live in certain habitats based on protection, shade cover, rugosity, and foraging return. Haemulidae, also known as grunts, are a family of fishes that are prevalent on Bonaire and can be found throughout tropical coral reef ecosystems. This study utilized in situ observations to investigate the preferred habitats of solitary grunts compared to colonial grunts based on the amount of the of protection and shade cover that the habitat provided. Three types of grunts were focused on in this study: blue striped grunts (Haemulon sciurusnch), French grunts (Haemulon flavolineatu), and smallmouth grunts (Haemulon chrysargyreum). The results of this study demonstrated that solitary smallmouth grunts utilized habitats that provided the most protection. Further, solitary smallmouth grunts were found in habitats shaded by coral more than the other grunt species. French grunts were found in overall shade cover more than both smallmouth grunts and blue striped grunts. This study showed that blue striped grunts rely mainly on their size for protection, smallmouth grunts on schooling, and French grunts on habitat. A general knowledge of grunts habitat preferences is beneficial because many reefs worldwide are currently degrading. If the reefs continue to degrade, grunts could be in danger because of their specific habitat preferences, based on both their species and social status. Preserving the complexity of coral reef habitats is crucial for some grunts, such as French and smallmouth grunts, but it is not crucial for other grunts, such as blue striped grunts.

This student research was retrieved from Physis: Journal of Marine Science XVII (Spring 2015)19: 34-42 from CIEE Bonaire.

Coral reef environments exhibit numerous ecological interactions between different organisms. The habitat structure of a healthy coral reef is composed of many different coral species, with various fish species inhabiting the reef. Coral reef studies often focus on a large spatial scale rather than smaller local scale environments within the reef. The objective of this study was to compare fish populations associated with the microhabitat surrounding individual coral heads of two different species. The purpose of this study was to determine if there were differences in fish abundance, fish species richness, and fish diversity between two massive stony corals, Diploria strigosa and Orbicella annularis. These two corals are common on many Caribbean reefs but are morphologically different; therefore, it was hypothesized that they would show differences between their associated fish assemblages. By conducting fish count observations on both D. strigosa and O. annularis, I was able to compare means between the coral associated fish populations using statistical tests. No statistically significant differences were found between these two coral species for mean fish abundance, species richness, or diversity. One possible explanation is that the larger scale reef environment and processes may have a significant effect on local fish populations found on individual coral heads. By studying the microhabitats of coral species and the associated fish assemblages, we can gain a better understanding of fish population dynamics of coral reefs across larger ecological scales—both regionally and globally

This student research was retrieved from Physis: Journal of Marine Science XVIII (Fall 2015)19: 61-69 from CIEE Bonaire.

Hermodice carunculata, commonly known as the Bearded Fireworm, is a corallivorous Polychaete found throughout the Atlantic Ocean and the Caribbean and is noted for its fluorescence. Studies have found that the highest abundance of H. carunculata is in water shallower than 1 m. The present study observed the habitat, size, and fluorescent patterns of H. carunculata in the intertidal zone of Yellow Submarine dive site on Bonaire. Three transects were laid at 55 cm and 110 cm deep, at 20 and 50 minutes after sunset. Additionally, fireworms were caught in wire traps to be more closely observed in the laboratory under a dissecting microscope. There was no significant difference between the depth (110 cm or 55 cm) and the size (less than or greater than 6 cm), nor was there a difference in abundance between the two time periods of data collection (20 minutes and 50 minutes after sunset). Furthermore, there was no significant difference between the fluorescent pattern (GREEN, GOB, OOB, or ROB) and the substrate (algae, coral, rubble, rock, or sand) the individual was found on, or fluorescent pattern and size. There was, however, a significant difference in density of fireworms per square meter over the five-week study period. Fireworm predation can have a large impact on the health of corals. This paper aims to increase the understanding of H. carunculata, so that the corals can be better protected, and the interaction between these two organisms can be better understood.

This student research was retrieved from Physis: Journal of Marine Science XVIII (Fall 2015)19: 54-60 from CIEE Bonaire.

The estimated number of species of Moray Eels (Family: Muraenidae) worldwide is around 200. A majority of morays hide in crevices and holes during the day, but come out to forage at night. The amount of activity during the day and night differs between species. Some are strictly nocturnal or diurnal while others are equally present during both times. Morays are generally piscivores and have large impacts on the biomass of reef fishes due to their maneuverability. In some studies, morays have been found to have the largest impact out of all other piscivores regarding the quantity of fishes consumed. In this study we dove at 15 m for 45 min during the day and at sunset three times each (six dives total). We also snorkeled the same distance covered while diving, but shallower along the shoreline. The number and species of moray within a 2-m band while diving and a 1m band while snorkeling were recorded. Spotted morays were the most common species seen overall (87.3% of all morays recorded). The density of morays was the highest while snorkeling (1.38 ± 0.77/10 m2 ). The density of morays while snorkeling was roughly 10 times greater than the day dives and almost 14 times greater than the sunset dives. Smaller morays were seen in the shallows while snorkeling and larger morays were seen while diving. The high number of small morays seen shallower indicates that morays may use shallow habitats as juveniles and move deeper on the reef once they mature and can consume larger prey.

This student research was retrieved from Physis: Journal of Marine Science XVIII (Fall 2015)19: 21-26 from CIEE Bonaire.