Hawaiian Fishes Research Articles

Fishes collected during the 2017 MarineGEO assessment of Kāne‘ohe Bay, O‘ahu, Hawai‘i

AbstractWe report the results of a survey of the fishes of Kāne‘ohe Bay, O‘ahu, conducted in 2017 as part of the Smithsonian Institution MarineGEO Hawaii bioassessment. We recorded 109 species in 43 families. The most speciose families were Acanthuridae (11 species), Gobiidae (11 species), Pomacentridae (10) and Chaetodontidae (9 species). Nine of the species that we collected are known or suspected to be introduced to the Hawaiian Islands. Specimens were identified, measured and photographed. All specimen vouchers were fixed in formalin and ultimately transferred to 75% ethanol for long-term storage. For nearly all species, we took multiple tissue samples from specimen vouchers prior to formalin-fixation; we preserved tissues in 95% ethanol and then stored them at −80°C. The 5′-end of the mitochondrial cytochrome oxidase I gene (mtCOI) was sequenced for 94 species to confirm their taxonomic identification. Using these barcode sequences, we also measured genetic distances between collected individuals and their conspecifics from other localities outside Hawaii to verify the hypothesis that Hawaiian populations of species broadly distributed throughout the Indo-Pacific may be genetically distinct. We present select case studies to demonstrate the potential for undiscovered endemism in the Hawaiian fish biota.

Characteristic of “Bontot” Combined of Hawaiian Ladyfish (Elops hawaiiensis) Meat and Tarpon Fish (Megalops cyprinoides)

Bontot is one of fish gel products in Banten Province. The main raw material of Bontot was Hawaiian ladyfish which is commonly found in the milkfish pond. However, the availability of the Hawaiian ladyfish was very limited. This study investigated the utilizaation of tarpon (Megalops cyprinoides), a fish of similar texture to the hawaiian ladyfish, for the production of bontot. The bontot quality was evaluated based on the organoleptic and microbial parameters. A combination of 37.5% ladyfish and 62.5% tarpon was considered as the best formula producing bontot with folding test 4.07 and bites 6.77, and the parameter of color, aroma, flavor, and texture similar to those of the commercial (3.43-4.00) products. The bontot contained moisture 50.50%, ash 2.42%, fat 0.32%, protein 5.67%, and carbohydrates 41.09% while the microbiological was below the 4.20 threshold, suggesting the bontot is safe for consumption.

Assemblage-level effects of the introduced peacock hind (Cephalopholis argus) on Hawaiian reef fishes

The peacock hind Cephalopholis argus (family Serranidae), locally known as ‘roi’, was introduced from French Polynesia to Hawaii in the mid-twentieth century as a food fish. However, because of its association with ciguatera fish poisoning, it is rarely fished for food. Previous research indicates that roi could have a negative impact on native reef fish assemblages because of their high densities and prey consumption rates. However, it is unclear whether roi add to the cumulative mortality of prey (predation hypothesis), or whether predation is instead compensatory (doomed surplus hypothesis). This study experimentally assessed the effects of roi on reef fish populations through a long-term (5.5 year) predator removal experiment. A Before-After-Control-Impact study design was used to assess changes in fish assemblages following the removal of roi on 1.3 ha of patch reef. Increases in the density of prey-sized fish (<15 cm TL) were observed 18 months after roi removal. However, those effects did not translate into sustained increases in prey. While increases in potential competitors, wrasses (family Labridae), particularly the piscivorous ringtail wrasse Oxycheilinus unifasciatus, were observed on roi-free reefs, the fish assemblage did not diverge substantially in composition. Native reef fish appeared to resist the potential negative impacts of predation by roi, possibly through a refuge in size for some fish families. Management to protect intact fish assemblage size-structure could serve to bolster native resistance to invading species. In considering the threats facing coral reefs, and the possible solutions, roi removal alone will not likely replenish native fishery resources.

Trimethylamine oxide accumulation as a function of depth in Hawaiian mid-water fishes

Trimethylamine oxide (TMAO) is a common osmolyte and counteracting solute. It is believed to combat the denaturation induced by hydrostatic pressure as some deep-sea animals contain higher TMAO levels than their shallow water counterparts. It has also been proposed that TMAO may accumulate passively during lipid storage resulting in a correlation between lipid content and TMAO levels in some groups. Previous research showed that lipid content decreased with depth in species of Hawaiian fishes presenting a novel test of these competing hypotheses. TMAO ranged from 20.4 to 92.8mmol/kg. Lipid content ranged from 0.50 to 4.7% WW. After completing a comprehensive search for depths available in the literature, provided here, we analyzed TMAO and lipid as a function of average, minimum and maximum depth of occurrence for 27 species of fishes from nine orders. We found that TMAO is positively correlated with all measures of habitat depth (hydrostatic pressure) but the relationship is strongest with average depth. We further showed using phylogenetic independent contrasts that this relationship was not influenced by the evolutionary relatedness of these species. Interestingly, we found that lipid content increased with depth, in direct contrast to previous studies. TMAO is thus also positively correlated with lipid content. While we are unable to distinguish between these hypotheses, we show that TMAO is strongly correlated with depth in mid-water fishes.

Parasitism of a native Hawaiian stream fish by an introduced nematode increases with declining precipitation across a natural rainfall gradient

AbstractClimate change can promote disease emergence if shifting conditions favour infection of native fauna by introduced parasites and pathogens. In Hawai'i, climate warming is predicted to reduce net precipitation and surface flow in streams, which in turn could increase parasitism of native stream fishes by non‐native parasites. In this study, we utilised a natural precipitation gradient across the Hamakua coast on the island of Hawai'i to assess the relationship between precipitation and infection of Awaous stamineus, a native amphidromous goby, by the introduced nematode Camallanus cotti. We found that the abundance, intensity and prevalence of C. cotti in A. stamineus increased with declining rainfall. Our results also show that parasitism tracks precipitation patterns across the archipelago and that parasitism increases even with moderate decreases in rainfall. As the Hamakua coast precipitation gradient represents a proxy for predicted climate‐driven reductions in precipitation, these findings suggest that infection of native Hawaiian fishes by introduced parasites will increase if climate conditions change as expected. Our findings also suggest that parasitism may be exacerbated by other factors that reduce surface flow, including water extraction for agricultural and urban uses. If so, then adaptive management of minimum flow standards in Hawai'i and elsewhere could improve the well‐being of at‐risk native fishes by alleviating parasitism under current and future climate conditions.

Stairway to heaven: evaluating levels of biological organization correlated with the successful ascent of natural waterfalls in the Hawaiian stream goby Sicyopterus stimpsoni.

Selective pressures generated by locomotor challenges act at the level of the individual. However, phenotypic variation among individuals that might convey a selective advantage may occur across any of multiple levels of biological organization. In this study, we test for differences in external morphology, muscle mechanical advantage, muscle fiber type and protein expression among individuals of the waterfall climbing Hawaiian fish Sicyopterus stimpsoni collected from sequential pools increasing in elevation within a single freshwater stream. Despite predictions from previous laboratory studies of morphological selection, few directional morphometric changes in body shape were observed at successively higher elevations. Similarly, lever arm ratios associated with the main pelvic sucker, central to climbing ability in this species, did not differ between elevations. However, among climbing muscles, the adductor pelvicus complex (largely responsible for generating pelvic suction during climbing) contained a significantly greater red muscle fiber content at upstream sites. A proteomic analysis of the adductor pelvicus revealed two-fold increases in expression levels for two respiratory chain proteins (NADH:ubiquinone reductase and cytochrome b) that are essential for aerobic respiration among individuals from successively higher elevations. Assessed collectively, these evaluations reveal phenotypic differences at some, but not all levels of biological organization that are likely the result of selective pressures experienced during climbing.

An Invasive Fish and the Time-Lagged Spread of Its Parasite across the Hawaiian Archipelago

Efforts to limit the impact of invasive species are frustrated by the cryptogenic status of a large proportion of those species. Half a century ago, the state of Hawai'i introduced the Bluestripe Snapper, Lutjanus kasmira, to O'ahu for fisheries enhancement. Today, this species shares an intestinal nematode parasite, Spirocamallanus istiblenni, with native Hawaiian fishes, raising the possibility that the introduced fish carried a parasite that has since spread to naïve local hosts. Here, we employ a multidisciplinary approach, combining molecular, historical, and ecological data to confirm the alien status of S. istiblenni in Hawai'i. Using molecular sequence data we show that S. istiblenni from Hawai'i are genetically affiliated with source populations in French Polynesia, and not parasites at a geographically intermediate location in the Line Islands. S. istiblenni from Hawai'i are a genetic subset of the more diverse source populations, indicating a bottleneck at introduction. Ecological surveys indicate that the parasite has found suitable intermediate hosts in Hawai'i, which are required for the completion of its life cycle, and that the parasite is twice as prevalent in Hawaiian Bluestripe Snappers as in source populations. While the introduced snapper has spread across the entire 2600 km archipelago to Kure Atoll, the introduced parasite has spread only half that distance. However, the parasite faces no apparent impediments to invading the entire archipelago, with unknown implications for naïve indigenous Hawaiian fishes and the protected Papahānaumokuākea Marine National Monument.

Where are they now? The fates of two genetic lineages in an introduced Hawaiian reef fish

Humans, both wittingly and unwittingly, have been transporting marine organisms beyond their native ranges for centuries (Ruiz et al. 1997). A central challenge of invasion biology is to identify the factors that determine whether introduced species fail to become established, become benign members of a community, or spread so far and reach such densities as to be considered invasive. Organismal features such as physiological tolerance, niche breadth and fecundity are critical, but by themselves are inaccurate predictors of the fates of introduced species (Sakai et al. 2001). The size, age distribution, and genetic makeup of founder populations are also important, but because they are usually unknown they are most often viewed as sources of uncertainty. For marine species with planktonic larvae, the challenge is even greater because the consequences of a planktonic phase for dispersal and population viability are not well understood. In this issue, Gaither et al. (2010a) present a remarkable account of the introduction of a reef fish for which the number and genetic makeup of the founders are known. Between 1956 and 1961, the Division of Fish and Game for the Territory of Hawaii introduced 12 non-indigenous fish species into Hawaiian waters to establish commercial and sport fisheries. The introduction of Lutjanus kasmira, the bluestriped snapper, was the most successful (Fig. 1). There were two releases of fish from French Polynesia. In 1958, 2431 fish from the Marquesas Islands were released on Oahu, followed in 1961 with an additional 728 fish from the Society Islands. The blue striped snapper rapidly spread to the other Hawaiian Islands, reaching the northwestern end of the archipelago by 1992. The choice of the Marquesas as one of two sources for the introduction was fortuitous. Gaither et al. (2010b) found that the Marquesas population is genetically distinct from all other Indo-Pacific populations of L. kasmira. Mitochondrial cytochrome b sequences of fish from the Marquesas belong to a separate lineage that diverged from others in the species roughly half a Ma. Allele frequencies for several nuclear loci are also distinct. This provided Gaither et al. (2010a) with an extraordinary opportunity to examine what became of the mixed genetic heritage of Hawaiian blue striped snappers after 50 years.

Morphological selection in an extreme flow environment: body shape and waterfall-climbing success in the Hawaiian stream fish Sicyopterus stimpsoni

Morphological selection in an extreme flow environment: body shape and waterfall-climbing success in the Hawaiian stream fish Sicyopterus stimpsoni

J. E. Randall: Reef and shore fishes of the Hawaiian Islands

While Jeremy Austen and I were editing Indo-Pacific Fishes No. 37 with the software package Adobe InDesign at the end of 2004, Dr. John E. (Jack) Randall and I discussed the suitability of various software packages for desktop publishing. At that time, I was informed by Jack Randall that he had already finished writing the text of his comprehensive new Hawaiian fish book, then under review. He began the design of the book using InDesign (Adobe Systems Inc.) in July 2005, then 81 years of age, after receiving instructions from his former student, Richard L. Pyle. He was, therefore, both author and book designer. In April 2007, ‘‘Reef and shore fishes of the Hawaiian Islands’’ was published, comprising 560 pages and treatments of 622 fish species in 101 families found from the shore to depths of 200 m depths within the Hawaiian Islands. It did not include offshore pelagic fishes, such as the family Exocoetidae, or deepwater fishes ([200 m). As a total 1,222 fish species have been reported from the Hawaiian Islands, including pelagic, deepwater, and freshwater forms, the book has fully covered half of the Hawaiian ichthyofauna. The book layout includes introductory chapters, family and species accounts, a glossary, and references. The introductory chapters deal with the history of ichthyological research in the islands (six pages), zoogeography (six pages), introduction of fishes (four pages), marine conservation (five pages), and methods for fish identification (five pages). For ichthyologists and marine biologists new to the fishes of the islands, the first three chapters provide a very useful background. The pages covering External Features of Fishes, including seven explanatory photographs, repeat the text of an earlier publication by Jack Randall (guide book on fishes of the islands of the South Pacific), but three of the seven original fish photographs have been replaced by new photographs of other species. The main section of the book is divided into two parts, i.e., cartilaginous and bony fishes, with a separate discussion differentiating between these two major lineages. Family accounts (with an English and scientific name heading) are presented in phylogenetic order, approximately following Nelson (2006), and usually include general morphology, key characters, distribution (worldwide and Hawaiian Islands), biology, and fisheries. These are followed by a key to the Hawaiian representatives of the family (if more than one) and provide for rapid identification, thereby significantly enhancing the value of the book. Earlier guide books published by Jack Randall on fishes of the Red Sea, Oman, Maldive Islands, Great Barrier Reef, and South Pacific, which were similar in style and format to the present publication, had not included keys to species. Species accounts are then ordered alphabetically by genus and species. The headline of each species account includes the English name on the left, followed by the Hawaiian name where known and the scientific name [including author(s) and year] on the right side in the same line. A telegraphic species description, including the maximum total length recorded, is followed by notes on distribution and general remarks. The former include the geographic range of the species and type locality. ‘‘Remarks’’ include comments on habitat, biology, synonyms, and specimens, resulting in an encyclopedic coverage overall. The book contains 1,007 illustrations, 944 of which are color photographs mostly taken by Jack Randall. Some H. Motomura (&) The Kagoshima University Museum, 1-21-30 Korimoto, Kagoshima 890-0065, Japan e-mail: motomura@kaum.kagoshima-u.ac.jp

Stable Isotope Analysis of Amphidromous Hawaiian Gobies Suggests Their Larvae Spend a Substantial Period of Time in Freshwater River Plumes

We employed stable isotope analysis (δ13C, δ15N) to evaluate the sources of nutrients used by amphidromous gobiid fishes (Lentipes concolor, Sicyopterus stimpsoni, Awaous guamensis) caught migrating into and living in Hakalau Stream, Hawaii. Although considerable variation amongst the stable isotope values of stream items was noted across all 4 years of our study, the relationships between the fishes were relatively constant. Stable isotope values of recruiting gobies were consistently closer to those of both inshore plankton and freshwater adults than those of offshore plankton, suggesting that the larvae of these species derive much of their nutrition from inshore environments influenced by fresh water. Small differences between the stable values of these species further suggested that their larvae come from different inshore locations. After entering fresh water all species appear to swim rapidly upstream without feeding. Finally, once well upstream, adult L. concolor and A. guamensis appear to assume an omnivorous diet while adult S. stimpsoni rely upon autochthonous production within streams. We propose that freshwater food webs play an integral yet complex role in the lives of both larval and adult amphidromous Hawaiian fishes.

Visual Biology of Hawaiian Coral Reef Fishes. I. Ocular Transmission and Visual Pigments

Abstract The visual biology of Hawaiian reef fishes was explored by examining their eyes for spectral sensitivity of their visual pigments and for transmission of light through the ocular media to the retina. The spectral absorption curves for the visual pigments of 38 species of Hawaiian fish were recorded using microspectrophotometry. The peak absorption wavelength (λmax) of the rods varied from 477–502 nm and the λmax of individual species conformed closely to values for the same species previously reported using a whole retina extraction procedure. The visual pigments of single cone photoreceptors were categorized, dependent on their λmax-values, as ultraviolet (347–376 nm), violet (398–431 nm) or blue (439–498 nm) sensitive cones. Eight species possessed ultraviolet-sensitive cones and 14 species violet-sensitive cones. Thus, 47% of the species examined displayed photosensitivity to the short-wavelength region of the spectrum. Both identical and nonidentical paired and double cones were found with bl...

The Global Spread of Parasites: What Do Hawaiian Streams Tell Us?

Abstract The global spread of parasites threatens native animals even in the most isolated of all habitats on Earth. In the Hawaiian archipelago, the five native species of stream fishes are infected with several species of alien parasites introduced through human activities. These exotic parasites have been shown to present greater disease threats to their Hawaiian fish hosts than do parasites that have colonized native fish by natural means. By studying the biological characteristics and mechanisms of transmission of parasite colonists, researchers can enhance understanding of the parasites' global dispersal.

Life History of the Hawaiian Fish Kuhlia sandvicensis as Inferred from Daily Growth Rings of Otoliths

Kuhlia sandvicensis, the aholehole, is a native Hawaiian fish found in both marine and freshwater habitats. In the lower reaches of streams, they are predators on stream fishes, invertebrates, and insects. Aholehole are an important food fish in the Hawaiian Islands and were often used by ancient Hawaiians in traditional ceremonies. Although aholehole are an important part of stream ecosystems and Hawaiian culture, little is known about their life history, specifically, whether a freshwater phase is obligatory. In this study, light microscopy and electron microprobe techniques were used to analyze otolith daily increments. The analysis estimated age of juveniles and provided information regarding salinity of a fish's habitat at specific points in its life. Sr/Ca profiles from otoliths of juvenile and adult fish from fresh and salt water indicated that this species' use of stream habitats is facultative. Unlike Hawaiian freshwater gobies and at least one other member of the Kuhliidae from the Western Pacific, there is no physiological requirement of fresh water at a specific point in the life cycle of K. sandvicensis. Future research will provide a greater understanding as to the importance of streams as nursery habitats for this species. The research is expected to bolster the argument for maintaining the stream-ocean corridor for access by amphidromous gobies and perhaps also for the aholehole.

Aseraggodes holcomi, a New Sole (Pleuronectiformes: Soleidae) from the Hawaiian Islands

Aseraggodes holcomi, a New Sole (Pleuronectiformes: Soleidae) from the Hawaiian Islands John E. Randall Abstract The soleid fish Aseraggodes holcomi, the third Hawaiian species of the genus, is described from six specimens collected off O'ahu, from sand in 0.6-27 m. It is distinct in having 68-72 dorsal-fin rays, 47-50 anal-fin rays, 76-80 lateral-line scales, the snout not overlapping the lower lip, and in its small size (largest, 58.6 mm SL, a mature female). Gilbert (1905) described two new species of Symphurus from deep water as the first representatives of the family Soleidae for the Hawaiian Islands. These fishes, popularly called tonguefishes, are now placed in a separate family, Cynoglossidae. Gosline and Brock (1960) added the first true soleid to the Hawaiian fish fauna, which they "very provisionally identified" as the Japanese Aseraggodes kobensis (Steindachner). Randall (1996) showed that their kobensis is a new species, naming it A. therese, and described another shallow-water species, A. borehami. Both are nocturnal and usually bury beneath sand in caves during the day. It is therefore easy to understand why they were overlooked for so many years. Fellow diver Ronald Holcom surprised J.E.R. by collecting a sole in 10 m at Pūpūkea on the north shore of O'ahu in 1997 that he thought was different in color from A. borehami and A. therese. J.E.R. confirmed that it is indeed different, not only by its color but by its lateral-line scale count of 77 (at most 66 in therese and 70 in borehami). Holcom collected three more specimens off Pūpūkea, two of which were caught in 27 m. Darrell Takaoka collected the largest specimen, 58.6 mm SL, shortly after midnight at Ala Moana Beach Park in only 0.6 m. David W. Greenfield and J.E.R. collected one additional specimen from Kāne'ohe Bay in 2 m. A review of the literature reveals that this third species of the genus Aseraggodes from Hawai'i is also undescribed. Materials and Methods Type specimens of the new species have been deposited in the Bernice P. Bishop Museum, Honolulu (BPBM), Calfornia Academy of Sciences, San Francisco (CAS), Museum National d'Histoire Naturelle, Paris (MNHN), National Science Museum of Tokyo (NSMT), and the National Museum of Natural History, Washington, D.C. (USNM). Lengths recorded for specimens are standard length (SL), measured from the front of the head at the base of the anterior dorsal-fin rays to the midbase of the caudal fin; body depth is the maximum depth from the base of the dorsal rays to the base of the anal rays; body thickness is the maximum thickness between the ocular and blind surfaces (but not over the abdomen); head length is measured on the ocular side from the upper end of the gill opening to the front of the head at the base of the dorsal rays; snout length is taken from the same anterior point to the front of the upper eye; eye diameter is the horizontal diameter of the upper eye (the dark eyeball, not the fleshy outer cutaneous part); inter-orbital width is the least width between the dark edges of the two eyes; upper-jaw length is measured on the blind side from the front of the upper lip to the rear of the maxilla; caudal-peduncle depth is the least depth, and caudal-peduncle length the horizontal distance between the rear base of the anal fin [End Page 247] and the base of the caudal fin; predorsal, preanal, and prepelvic lengths are measured from the base of the first ray of these fins to the most anterior point of the upper lip; lengths of dorsal and anal rays are measured from the extreme base of the rays to the tips without trying to straighten the rays; caudal-fin length is the length of the longest median ray; pelvic-fin length is the length of the longest ray on the ocular side. Lateral-line scales are counted on the ocular side from directly above the upper end of the gill opening to the base of the caudal fin; the counts...

Spectral Sensitivity of the Hawaiian Saddle Wrasse, Thalassoma duperrey, and Implications for Visually Mediated Behaviour on Coral Reefs

Although tropical coral reefs are one of the most spectrally complex habitats, there is relatively little known about colour vision of reef fish. In this study, we measured the spectral sensitivity of an endemic Hawaiian coral reef fish, Thalassoma duperrey (family Labridae), and assessed the possible role of visual sensitivity in mediating intraspecific communication. Electrophysiological recordings of compound action potentials from retinal ganglion cells were used to generate spectral sensitivity curves for specific wavelengths (380–620 nm). We found at least 2 sensitivity peaks for the on response (λmax=460, 550 nm). The off response lacked a short wavelength mechanism but a medium wavelength mechanism (λmax=545 nm) and a longwave mechanism (λmax=570 nm) were found. To quantify the visual stimulus provided by a conspecific individual, spectral reflectance from the colour pattern of T. duperrey was measured with a spectroradiometer. Luminance and spectral contrast were computed between colour patches of the pattern and between the patches and natural backgrounds (i.e., water and coral). Reflectance from the blue head and contrast from the blue, green and red patches matched the sensitivity maxima of T. duperrey, although this depended on the type of background. Our results indicate that T. duperrey should be able to visually detect the colour pattern of a conspecific fish and that T. duperrey's visual system is designed to enhance target detection in the coral reef habitat with matched and offset cone mechanisms.

Effects of incident light and background conditions on potential conspicuousness of Hawaiian coral reef fish

Many coral reef fish are assumed to be conspicuous in their natural environment due to their bold and distinct colour patterns. However there have been few attempts to quantify the conspicuousness of coral reef fish under natural photic conditions. In this study, the effects of incident light and background conditions on the potential conspicuousness of four species of Hawaiian reef fish (Chaetodon auriga, Labroides phthirophagus, Thalassoma duperrey, Zebrasoma flavescens) were examined. The optical properties of water, coral and fish colour patterns were measured with an underwater spectroradiometer. Potential conspicuousness was quantified by calculating luminance (brightness) contrast and spectral (colour) contrast within fish colour patterns, and between patterns and natural backgrounds, i.e. water and coral. Under different illuminating and background conditions, the contrast from these fishes was highly variable. Different incident light conditions resulted in significant differences in inherent spectral contrast for L. phthirophagus. All fish had significantly different luminance contrast when the optical properties of the water backgrounds varied. Against coral backgrounds, T. duperrey and Z. flavescens had significantly different luminance contrast and L. phthirophagus and T. duperrey had significantly different spectral contrast. These results have important implications for theories on the adaptive significance of reef fish coloration since the conspicuousness of reef fish appears to be highly dependant on local photic conditions and therefore, some colour patterns may not be conspicuous in the wild as is often presumed.

Food relations between coexisting native Hawaiian stream fishes

In this study, an ecomorphological perspective is used to examine the role of feeding morphology in shaping patterns of food resource use and coexistence for Awaous guamensis and Sicyopterus stimpsoni, two native gobies (Gobiidae) which inhabit mountainous streams of the high Hawaiian Islands. Using data from underwater census, gut content analysis, and benthic sampling, I determined that A. guamensis, the generalist, had nearly unchallenged use of invertebrate foods. Overlap in fitness for algal use, however, resulted in a partitioning of benthic algae, with A. guamensis having domain over most green algae (43.0% of diet), whereas S. stimpsoni the algal specialist, fed predominantly on blue-green algae (22.6% of diet) and diatoms (54.2% of diet). Cladophora sp. (Chlorophyta) and pennate diatoms (Chrysophyta) were determined to be the ‘primary algal foods’ of A. guamensis and S. stimpsoni, respectively, and were utilized in a mutually exclusive manner with other ‘secondary algal foods’ depending upon availability. Heterogeneity, found in the abundance and composition of algal and invertebrate foods in the benthic landscape both spatially and seasonally, may be regulated by stream flow and periodic disturbance. This changing mosaic of foods is suggested as having provided opportunities for minimizing competitive conflicts and enhancing the potential for stream species to coexist. Competition for preferred foods, created by inter-specific overlap in ecomorphology and spurred by constraints placed on food diversity by the extreme geographic isolation of the Hawaiian Islands, is hypothesized as having played an evolutionary role in shaping resource use patterns which facilitate coexistence.

Growth rates of four Hawaiian deep slope fishes: a comparison of methods for estimating age and growth from otolith microincrement widths

Growth rates of four Hawaiian deep slope fishes: a comparison of methods for estimating age and growth from otolith microincrement widths

Evolutionary Genetics of Hawaiian Freshwater Fish

We surveyed mitochondrial (mt)DNA restriction site variation within each of the five native species of Hawaiian freshwater fishes: Lentipes concolor, Stenogobius hawaiiensis, Sicyopterus stimpsoni, Awaous guamensis, and Eleotris sandwicensis. MtDNA haplotypes did not vary geographically except among samples of S. hawaiiensis, where haplotypes from Maui clustered together. One haplotype in this cluster also was found on Kauai and on Oahu, and one haplotype was found only on Kauai. MtDNA data suggest gene flow among islands, consistent with interisland dispersal through amphidromous larvae. We hypothesize that dispersal has prevented further speciation in these fishes and that colonization of island freshwater habitats by larvae could be independent of natal island.