Zoology

The ongoing loss of biodiversity calls for assessing the performance of conservation strategies. In the case of marine protected areas (MPAs), a common indicator of success is the amount of biodiversity protected within them. However, there are many cases where the information for the official MPA boundary is not available, making it difficult to precisely measure the indicator. A solution to this problem is to create circular buffers around the centre location of MPAs for which boundaries are missing, equivalent in area to that reported officially for the MPA. The Coral Triangle Atlas provides the opportunity to quantify more precisely the validity of using buffers as proxies for MPA boundaries both at national and regional scales in the Coral Triangle. We used 612 existing MPA boundaries, converted them into point data at their centroids and then created circular buffers of area equal to that of the MPAs' original polygons. Errors in estimated area of protected coral reefs were used to measure the bias created by the centroid buffers. We obtained an underestimation of protected coral reef area, both at the scale of the Coral Triangle region and at a national scale when using centroid buffers, with a larger underestimation as more MPA boundary proxies were used. We found that the size of MPA does not have a significant effect on the percentage of bias when MPAs are smaller than 100 km 2 at a national level, and smaller than 1000 km 2 at a regional level. With less than 15% of the total MPAs in the CT region larger than 100 km 2 , these results suggest that using buffers at a national scale for small MPAs may be a good solution to missing boundaries and cheaper than trying to collect exact information if working at a national or multinational scale. However, for countries with large MPAs such as Indonesia, using this proxy system will tend to create a larger error. At a regional scale, such as the Coral Triangle region, an estimation of total protected coral reef using buffers as MPA boundaries proxies will produce a small underestimation, thus, producing conservative results of protected coral reef area. This study shows the importance of assessing the bias introduced by using proxies for MPA boundaries when measuring indicators of conservation target achievement for coastal and marine areas.

Information on connectivity is becoming increasingly in demand as marine protected areas are being designed as an integral part of a network to protect marine resources at the ecosystem level. Larval dispersal and population structure, however, remain very difficult to assess. Here, we tested the predictions of a detailed oceanographic connectivity model of larval dispersal and coral recruitment within Palau and between Palau and Yap, which was developed to support the review of the existing network of marine protected areas in Palau. We used high throughput microsatellite genotyping of the coral Acropora hyacinthus to characterize population genetic structure. Pairwise F ST values between Palau and Yap (0.10), Palau and Ngulu (0.09) and Yap and Ngulu (0.09) were all significant and similar to pairwise F ST values of sites within Palau (0.02– 0.12) and within Yap (0.02–0.09) highlighting structure at island scale and indicating that recruitment may be even more localized than previously anticipated. A bottleneck test did not reveal any signs of a founder effect between Yap and Palau. Overall, the data supports the idea that recovery of A. hyacinthus in Palau did not come exclusively from a single source but most likely came from a combination of areas, including sites within Palau. In light of these results there seems to be very little connectivity around the barrier reef and management recommendation would be to increase the number or the size of MPAs within Palau.

The removal of a single dominant individual has been shown to trigger a sex change in some coral-reeffish. In the saddleback wrasse (Thalassoma duperrey), however, female-to-male sex change requires visual stimulation from smaller conspecifics. This change is not dependent on the sex or color of the stimulus fish and can be inhibited by larger conspecifics. On the reef, a female probably changes sex when the relative numbers of larger and smaller conspecifics change within her home range.

Chaetodon auriga, a conun7won marine fish in Hawaii, can be conditioned by presentation of a moving model of a cleaner fish as a positive reinforcement on an instrumental schedule. Reinforcement is probably through tactile stimulation and might help to shape the response of fish to cleaners. Tactile stimulilation night serve as a valuable reinforcer in studies of fish learning.

The Hawaiian damselfish, Stegastes fasciolatus, defends an all-purpose territory on shallow-water reefs. By conceptually dividing each territory into 3 horizontal and 2 vertical zones, each intruder into the territory was recorded by species, zones violated, and reaction of the resident. Intruders included 3 herbivorous, 7 omnivorous, and 2 carnivorous species. A BMDP ‘4F’ analysis for multiway tables was applied to examine the relationships between the proximate causal factors eliciting the chase response by a resident. Species of intruder and their position in the territory had an additive effect on the chase response, with position in the territory as the less important factor. Distance from the bottom was not indicated as an important factor. The ecological implications of these results are discussed.

The bold colours of reef fish probably serve various functions ranging from crypsis to advertisement. The presence of UV-sensitive vision in many reef fish demands that we explore these functions beyond the range of human vision. Current knowledge of the transmission of UV and visible radiation through clear ocean water, and knowledge of the likely spectral sensitivity of predatory and prey fish suggest that contrasting UV signals should be selected for social communication. For many juvenile reef fish, close-range detection and being noticed by predators may be much more important than long-range detection.Dascyllus aruanus (three-bar damsel) and D. reticulatus (two-bar damsel) juveniles are boldly coloured white fish with black bars that shelter in mixed-species groups in finely branched corals. Predators on the reef are probably well schooled in the location of their residence coral heads and the major threat is being noticed by a predator when making a defensive error. I took video images of the fish in the field through a series of narrow-band-pass filters from 340 to 600 nm, which spans the probable range for visual sensitivity in fish. With the help of colour reference standards and spectral irradiance data, I applied video pixel intensity measures to a model of colour vision to quantify luminance contrast when viewed by both conspecific fish and various predators. The two-bar damsel had a highly UV-reflective colour patch on its flag-like dorsal fin that was lacking in the three-bar. This result, taken together with their longer wavelength coloration, indicates that the two-bar is better adapted for short-range social communication, which would be difficult for predators to detect. Copyright 2003 Published by Elsevier Ltd on behalf of The Association for the Study of Animal Behaviour. 

Quinaldine and phenoxyethanol, two commonly used fish anesthetics, reduced the intensity of a chemically induced fright response in a marine goby. MS-222, an anesthetic that has been indicated as harmful to fish olfaction, had no significant effect. Understanding these effects must await further study, but it is clear that caution should be exercised. One should definitely not use quinaldine or phenoxyethanol instead of MS-222 in an effort to avoid harmful effects.

Tropical reef fishes are exposed to high levels of damaging ultraviolet radiation. Here we report the widespread distribution of both UVA- and UVB-absorbing compounds in the epithelial mucus of these fishes. Mucus from 137 reef fish species was examined by spectrophotometry and 90% were found to have strong absorbance peaks between 290 and 400 nm. Most fish species (78%) had more than one peak, that suggests a broad-band ultraviolet screening function for their mucus. Thalassoma duperrey, a tropical wrasse, was able to alter the absorbance of its epithelial mucus in response to both naturally and experimentally manipulated UV regimes. Visual modeling suggests that a fish with UV vision, such as Dascyllus albisella, could detect the changes in mucus spectra of T. duperrey that occurred in these experiments.

The visual ecology of fishes places changing demands on their visual system during development. Study of changes in the eye can suggest possible changes in behavioral ecology. The spectral transmission of the pre-retinal ocular media controls the wavelength of light that reaches the retina and is a simply measured indication of their potential visual capabilities. Dascyllus albisella is a coral reef planktivore known to have UV-sensitive retinal cone cells. UV vision probably aids in detection of zooplankton. As a juvenile it is very closely associated with branching coral heads or, more rarely, sea anemones. As it matures, it ventures farther from its coral, above the reef, and eventually assumes a more vagile life style, moving farther and more frequently afield. Their eyes contain short-wavelength blocking compounds in the lens, cornea and humors. As they age, both the lens and the cornea accumulate blocking compounds that increase the 50% transmission cutoff of the whole eye from ca. 330 nm in 2–3 cm juveniles to ca. 360 nm in the largest adults. The cornea increases its cutoff wavelength faster than the lens and becomes the primary filter in large adults. The cutoff of the aqueous and vitreous humors combined does not change with size. The slope of the transmission cutoff curve increases with the size of the fish. The increased blocking of UV radiation is likely not an adaptation to protect the eye from short-wavelength induced damage. Instead it probably reduces the image degradation effects of short-wavelength light in the largest eyes and still allows sufficient penetration of UV radiation to permit functional UV vision.