Ken Longenecker

A comprehensive investigation of mesophotic coral ecosystems in the Hawaiian Archipelago

Although the existence of coral-reef habitats at depths to 165 m in tropical regions has been known for decades, the richness, diversity, and ecological importance of mesophotic coral ecosystems (MCEs) has only recently become widely acknowledged. During an interdisciplinary effort spanning more than two decades, we characterized the most expansive MCEs ever recorded, with vast macroalgal communities and areas of 100% coral cover between depths of 50–90 m extending for tens of km2 in the Hawaiian Archipelago. We used a variety of sensors and techniques to establish geophysical characteristics. Biodiversity patterns were established from visual and video observations and collected specimens obtained from submersible, remotely operated vehicles and mixed-gas SCUBA and rebreather dives. Population dynamics based on age, growth and fecundity estimates of selected fish species were obtained from laser-videogrammetry, specimens, and otolith preparations. Trophic dynamics were determined using carbon and nitrogen stable isotopic analyses on more than 750 reef fishes. MCEs are associated with clear water and suitable substrate. In comparison to shallow reefs in the Hawaiian Archipelago, inhabitants of MCEs have lower total diversity, harbor new and unique species, and have higher rates of endemism in fishes. Fish species present in shallow and mesophotic depths have similar population and trophic (except benthic invertivores) structures and high genetic connectivity with lower fecundity at mesophotic depths. MCEs in Hawai‘i are widespread but associated with specific geophysical characteristics. High genetic, ecological and trophic connectivity establish the potential for MCEs to serve as refugia for some species, but our results question the premise that MCEs are more resilient than shallow reefs. We found that endemism within MCEs increases with depth, and our results do not support suggestions of a global faunal break at 60 m. Our findings enhance the scientific foundations for conservation and management of MCEs, and provide a template for future interdisciplinary research on MCEs worldwide.

Life history of the Hawaiian blackhead triplefin, Enneapterygius atriceps(Blennioidei, Tripterygiidae)

SynopsisWe described aspects of the life history of the small, cryptic, triplefin blenny, Enneapterygius atriceps, collected from the mouth of Kaneohe Bay, Oahu, Hawaii. We examined otolith microstructure to construct a von Bertalanffy growth curve, described a length–weight relationship, performed a detailed dietary analysis, used standard histological techniques to determine size at maturity and reproductive patterns, determined batch fecundity, and used an index of gonadal development to examine spawning seasonality. Enneapterygius atriceps is a remarkably short-lived species with low fecundity and a short, well-defined breeding season. Dietary analysis suggests this fish lives and feeds around the bases of dead coral heads. This study generated the first otolith-based growth curve for any member of the Tripterygiidae.

Relationships between Otolith Size and Body Size for Hawaiian Reef Fishes

ABSTRACT Estimating body size of fishes from remains recovered from piscivores, archaeological sites, and sedimentary deposits is desirable but rarely accomplished because the relationships between the size of a fish and its durable anatomical structures are largely unknown. Regression equations to predict the size or weight of 41 common Hawaiian reef fishes from sagittae (saccular otoliths) are presented. Data are also grouped into higher taxa to permit size predictions when otoliths cannot be assigned to species.

Archaeological evidence of validity of fish populations on unexploited reefs as proxy targets for modern populations.

Reef-fish management and conservation is hindered by a lack of information on fish populations prior to large-scale contemporary human impacts. As a result, relatively pristine sites are often used as conservation baselines for populations near sites affected by humans. This space-for-time approach can only be validated by sampling assemblages through time. We used archaeological remains to evaluate whether the remote, uninhabited Northwestern Hawaiian Islands (NWHI) might provide a reasonable proxy for a lightly exploited baseline in the Main Hawaiian Islands (MHI). We used molecular and morphological techniques to describe the taxonomic and size composition of the scarine parrotfish catches present in 2 archaeological assemblages from the MHI, compared metrics of these catches with modern estimates of reproductive parameters to evaluate whether catches represented by the archaeological material were consistent with sustainable fishing, and evaluated overlap between size structures represented by the archaeological material and modern survey data from the MHI and the NWHI to assess whether a space-for-time substitution is reasonable. The parrotfish catches represented by archaeological remains were consistent with sustainable fishing because they were dominated by large, mature individuals whose average size remained stable from prehistoric (AD approximately 1400-1700) through historic (AD 1700-1960) periods. The ancient catches were unlike populations in the MHI today. Overlap between the size structure of ancient MHI catches and modern survey data from the NWHI or the MHI was an order of magnitude greater for the NWHI comparison, a result that supports the validity of using the NWHI parrotfish data as a proxy for the MHI before accelerated, heavy human impacts in modern times.

Rapid reproductive analysis and length – weight relation for red - bellied fusilier, Caesio cuning, and longfin emperor, Lethrinus erythropterus (Actinopterygii: Perciformes: Caesionidae and Lethrinidae) from a remote village in Papua New Guinea

We present length–weight relations (LWR) and use rapid, low-cost histological methods to describe the reproductive biology of the red-bellied fusilier, Caesio cuning (Bloch, 1791), and the longfin emperor, Lethrinus erythropterus Valenciennes, 1830, based on 137 and 139 specimens, respectively, collected from a remote area in Papua New Guinea. The LWR for C. cuning is W = 0.0208FL3.0322. We estimate male L50 at 12.6 cm FL and female L50 at 15.3 cm FL. Overall sex ratio of mature individuals is not significantly different from 1 : 1; however, sex-ratio does vary with length. Females dominate size-classes from 17 through 20 cm and males are more abundant in smaller and larger size classes. The species is a batch-spawning gonochore. Batch fecundity is an exponential function of length BF = 0.1163FL4.2796. The LWR for L. erythropterus is W = 0.0145FL3.0976 for all specimens, but the length–weight relation differs between sexes. We estimate minimum size-at-maturity for males at 19.2 cm FL, and female L50 at 20.4 cm FL. Overall sex ratio of mature individuals is not significantly different from 1 : 1; however sex-ratio does vary with length. Males dominate size classes > 21 cm. The species is a batch-spawning, protogynous hermaphrodite.

Rapid Reproductive Analysis and Length-Dependent Relationships of Lutjanus biguttatus (Perciformes: Lutjanidae) from Papua New Guinea

Abstract: We describe a simple, inexpensive method for field-based histological analysis of fish gonads, and we used this method to describe the reproductive biology of the small snapper Lutjanus biguttatus from a remote area in Papua New Guinea (i.e., where laboratory equipment is limited and electrical service is lacking). We estimate male L50 at 13 cm FL and female L50 at 17 cm FL. Sex ratio is not significantly different from 1 : 1. There is no evidence for hermaphroditism. Fork length is a linear function of total length, FL = -0.1823 + 0.9647(TL), and weight is a cubic function of fork length, W = 0.0129(FL)3.0049. This information was generated during a 2-week period when the majority of our time was occupied by fish surveys. Our analyses were limited by availability of specimens (not processing time); therefore the methods we employed can help fill one of the information voids that preclude life-history-based management of coral-reef fishes.

Rapid Reproductive Analysis and Length–Weight Relation for Blacktail Snapper, Lutjanus Fulvus (Actinopterygii: Perciformes: Lutjanidae), from a Remote Village in Papua New Guinea

We present a length–weight relation and use rapid, low-cost histological methods to describe the reproductive biology of the blacktail snapper, Lutjanus fulvus (Forster, 1801), based on 124 specimens collected from a remote area in Papua New Guinea [W = 0.0134(FL)3.100]. We estimate male L50 at 13.5 cm FL and female L50 at 18.8 cm FL. Sex ratio is not significantly different from 1 : 1. The species is a gonochore. Mature females from 17.8 to 21.7 mm FL produce a mean 35 305 ± 29 141 eggs per spawning event.

Estimating Sustainable Live-Coral Harvest at Kamiali Wildlife Management Area, Papua New Guinea.

Live coral is harvested throughout the Indo-West Pacific to make lime, used in the consumption of the world’s fourth-most consumed drug, betel nut. Coral harvesting is an environmental concern; however, because lime-making is one of the few sources of income in some areas of Papua New Guinea (PNG), the practice is unlikely to stop. To better manage coral harvest, we used standard fishery-yield methods to generate sustainable-harvest guidelines for corymbose Acropora species found on the reef flat and crest at Lababia, PNG. We constructed a yield curve (weight-specific net annual-dry-weight production) by: 1) describing the allometric relationship between colony size and dry weight, and using that relationship to estimate the dry weight of Acropora colonies in situ; 2) estimating annual growth of Acropora colonies by estimating in situ, and describing the relationship between, colony dry weight at the beginning and end of one year; and 3) conducting belt-transect surveys to describe weight-frequencies and ultimately to predict annual weight change per square meter for each weight class. Reef habitat covers a total 2,467,550 m2 at Lababia and produces an estimated 248,397 kg/y (dry weight) of corymbose Acropora, of which 203,897 kg is produced on the reef flat/crest. We conservatively estimate that 30,706.6 kg of whole, dry, corymbose, Acropora can be sustainably harvested from the reef flat/crest habitat each year provided each culled colony weighs at least 1805 g when dry (or is at least 46 cm along its major axis). Artisanal lime-makers convert 24.8% of whole-colony weight into marketable lime, thus we estimate 7615.2 g of lime can be sustainably produced annually from corymbose Acropora. This value incorporates several safety margins, and should lead to proper management of live coral harvest. Importantly, the guideline recognizes village rights to exploit its marine resources, is consistent with village needs for income, and balances an equally strong village desire to conserve its marine resources for future generations.

Hermaphroditism in the dash-and-dot goatfish Parupeneus barberinus

Presence of bisexual individuals and a sex-specific bimodal size distribution are suggestive of protogyny in the dash-and-dot goatfish Parupeneus barberinus, but the most parsimonious interpretation of histological analysis is juvenile hermaphroditism. This is the first report of hermaphroditism in the Mullidae.

Rapid reproductive analysis and length–weight relations for five species of coral-reef fishes (Actinopterygii) from Papua New Guinea: Nemipterus isacanthus, Parupeneus barberinus, Kyphosus cinerascens, Ctenochaetus striatus (Perciformes), and Balistapus undulatus (Tetraodontiformes)

Longenecker K., Langston R., Bolick H., Crane M., Donaldson T.J, Franklin E.C., Kelokelo M., Kondio U., Potuku T. 2017. Rapid reproductive analysis and length–weight relations for five species of coral-reef fishes (Actinopterygii) from Papua New Guinea: Nemipterus isacanthus, Parupeneus barberinus, Kyphosus cinerascens, Ctenochaetus striatus (Perciformes), and Balistapus undulatus (Tetraodontiformes). Acta Ichthyol. Piscat. 47 (2): 107–124.