Kentaro Honda

Habitat Use by Fishes in Coral Reefs, Seagrass Beds and Mangrove Habitats in the Philippines

Understanding the interconnectivity of organisms among different habitats is a key requirement for generating effective management plans in coastal ecosystems, particularly when determining component habitat structures in marine protected areas. To elucidate the patterns of habitat use by fishes among coral, seagrass, and mangrove habitats, and between natural and transplanted mangroves, visual censuses were conducted semiannually at two sites in the Philippines during September and March 2010–2012. In total, 265 species and 15,930 individuals were recorded. Species richness and abundance of fishes were significantly higher in coral reefs (234 species, 12,306 individuals) than in seagrass (38 species, 1,198 individuals) and mangrove (47 species, 2,426 individuals) habitats. Similarity tests revealed a highly significant difference among the three habitats. Fishes exhibited two different strategies for habitat use, inhabiting either a single (85.6% of recorded species) or several habitats (14.4%). Some fish that utilized multiple habitats, such as Lutjanus monostigma and Parupeneus barberinus, showed possible ontogenetic habitat shifts from mangroves and/or seagrass habitats to coral reefs. Moreover, over 20% of commercial fish species used multiple habitats, highlighting the importance of including different habitat types within marine protected areas to achieve efficient and effective resource management. Neither species richness nor abundance of fishes significantly differed between natural and transplanted mangroves. In addition, 14 fish species were recorded in a 20-year-old transplanted mangrove area, and over 90% of these species used multiple habitats, further demonstrating the key role of transplanted mangroves as a reef fish habitat in this region.

Life history and migration of Sakhalin taimen, Hucho perryi, caught from Lake Akkeshi in eastern Hokkaido, Japan, as revealed by Sr:Ca ratios of otoliths

Microchemical analysis of the strontium (Sr) and calcium (Ca) ratios of otoliths was conducted to determine the life history and migration of anadromous Sakhalin taimen, Hucho perryi. In 2008 and 2009, 10 specimens were sampled from Lake Akkeshi in eastern Hokkaido, Japan. Our results indicated that some specimens migrated to brackish waters during their early life histories. Because the Sr:Ca ratios of the specimens in this study were all less than those of specimens from Sakhalin Island during a previous study, specimens from Lake Akkeshi may have migrated to brackish water, or may have remained in the ocean for only a short period.

Migratory patterns of exotic brown trout Salmo trutta in south-western Hokkaido, Japan, on the basis of otolith Sr:Ca ratios and acoustic telemetry.

Acoustic telemetry and microchemical analysis of otolith strontium-calcium ratios were used to evaluate how exotic brown trout Salmo trutta have responded to Japanese riverine environments of south-western Hokkaido by observing their migratory patterns. The existence of anadromous S. trutta was also verified. Most S. trutta caught in rivers for otolith analysis were freshwater residents (95·6%), whereas those caught in the sea were mainly smolts (91·3%), which had just migrated from rivers during spring. Anadromous S. trutta (n = 6) were captured in rivers and in the sea, confirming the existence of mature pre- and post-spawning fish. According to telemetry results, both mature and immature S. trutta used the river in winter, and their estimated sea-run timings showed individual differences. Through the combination of these two methods, migratory patterns on various spatio-temporal scales were observed. This first documentation of the presence of both male and female anadromous S. trutta in the same region within Japan indicated the risk of further colonization of exotic S. trutta via oceanic migration.

Movement patterns of adult Sakhalin taimen, Parahucho perryi, between stream habitats of the Bekanbeushi River system, eastern Hokkaido, Japan

The behavior of endangered adult Sakhalin taimen Parahucho perryi was tracked during 2008–2010 using acoustic telemetry in the Bekanbeushi River system, which flows through eastern Hokkaido, Japan. Movement distances per unit time of tracked P. perryi were compared between mid- and downstream habitats. Results indicated that movement distances were significantly longer in downstream habitats during all seasons. The movement distances in each stream decreased from spring to autumn. Moreover, tracked P. perryi exhibited crepuscular movement patterns; however, patterns were less pronounced in downstream habitats than in up- and midstream habitats. These findings strongly suggested that adult P. perryi exhibit nearly distinctive movement patterns across stream habitats; thus, fish may adopt different foraging tactics in each stream habitat. Fish moved more frequently in spring, which included the post-wintering and post-spawning season, most likely to search for food and more desirable habitat for recovery.

Fifteen novel microsatellite markers for two Amphiprion species (Amphiprion frenatus and Amphiprion perideraion) and cross-species amplification

Abstract Anemonefishes are popular model species for research on population connectivity via larval dispersal, and understanding this connectivity is beneficial when designing marine protected areas. We developed 15 microsatellite markers for two anemonefishes, Amphiprion frenatus and Amphiprion perideraion. Of these 15 markers, 10 worked well for both species, while three were specific for A. frenatus and two were specific for A. perideraion. For A. frenatus, the number of alleles at each locus ranged from 4 to 28, and the observed and expected heterozygosities ranged from 0.258 to 0.938 and from 0.285 to 0.953, respectively. For A. perideraion, the respective numbers were 4–14, 0.344–0.969, and 0.412–0.868. These microsatellite markers will be useful for the study of population connectivity in these two species.

Riverine environmental characteristics and seasonal habitat use by adult Sakhalin taimen Hucho perryi.

The study identified seasonal habitat use by endangered adult Sakhalin taimen Hucho perryi and the environmental characteristics of their habitat (water depth, amount of riparian forest and sinuosity). Fifteen adult H. perryi with acoustic tags were tracked by towing an acoustic receiver with a canoe in the Bekanbeushi River system in eastern Hokkaido Island, Japan, during each month from late April to late November 2008. Individuals mainly used midstream (shallower than downstream) habitats in all seasons. These locations were generally characterized by relatively dense riparian forests and high sinuosity, indicating the presence of pools. In spring, individuals used habitats with less riparian forest cover compared to mean value of the river channel. From spring to autumn, adult H. perryi selected limnologically complex habitats with meandering channels. From summer to autumn, individuals selected habitats with more riparian forest cover. The inverse relationship between H. perryi detection and riparian forest area in spring was a result of seasonal defoliation in deciduous riparian forests.

Variation in macrofaunal communities of sea grass beds along a pollution gradient in Bolinao, northwestern Philippines

This study examined the variation of macrofaunal communities in sea grass beds along a pollution gradient in Bolinao, northwestern Philippines. We established four stations and compared the diversity and abundance of macrofauna between them. The Shannon diversity index in the least polluted station was more than twice higher than that in the most polluted one. Abundance was more than thrice higher in the most polluted station. The species composition generally varied, with community difference explained largely by the predominance of the filter-feeding bivalve Gafrarium pectinatum and polychaete Capitella capitata. Species heterogeneity was reduced along the pollution gradient by approximately 19% from the least polluted to the most polluted station. This reduction indicates biodiversity alteration, which has a significant impact on ecosystem functioning. Aspects of species heterogeneity should be considered in environmental impact assessments and the management of coastal areas encountered with anthropogenic disturbances.

Diet, growth, and abundance of two seagrass bed fishes along a pollution gradient caused by milkfish farming in Bolinao, northwestern Philippines

The present study clarified the impacts of aquaculture pollution on the surrounding seagrass bed fishes by comparing the diet, growth, and abundance of Parupeneus barberinus and Acreichthys tomentosus along a pollution gradient caused by intensive milkfish Chanos chanos farming in Bolinao, northwestern Philippines. The two fish species and potential food items exhibited increasingly enriched δ13C values with greater distance from the milkfish farming area, thereby indicating that stable carbon isotopes facilitated good discrimination between fishes from polluted and unpolluted areas. P. barberinus fed on epi-/benthic crustaceans, whereas A. tomentosus consumed a wide range of food, including invertebrates and plant materials in the unpolluted areas, but zooplankton were the most commonly predated food items in the polluted areas for both species. The growth rate of P. barberinus was marginally lower in the polluted area than in the unpolluted area, whereas that of A. tomentosus did not differ between the two areas. The abundance of both species did not differ significantly between the polluted and unpolluted areas, but the growth patterns of the two species suggest that A. tomentosus has greater physiological tolerance of the polluted environment than P. barberinus.

Marine protected area restricts demographic connectivity: Dissimilarity in a marine environment can function as a biological barrier

Abstract The establishment of marine protected areas (MPAs) can often lead to environmental differences between MPAs and fishing zones. To determine the effects on marine dispersal of environmental dissimilarity between an MPA and fishing zone, we examined the abundance and recruitment patterns of two anemonefishes (Amphiprion frenatus and A. perideraion) that inhabit sea anemones in different management zones (i.e., an MPA and two fishing zones) by performing a field survey and a genetic parentage analysis. We found lower levels of abundance per anemone in the MPA compared to the fishing zones for both species (n = 1,525 anemones, p = .032). The parentage analysis also showed that lower numbers of fishes were recruited from the fishing zones and outside of the study area into each anemone in the MPA than into each anemone in the fishing zones (n = 1,525 anemones, p < .017). However, the number of self‐recruit production per female did not differ between the MPA and fishing zones (n = 384 females, p = .516). Because the ocean currents around the study site were unlikely to cause a lower settlement intensity of larvae in the MPA, the ocean circulation was not considered crucial to the observed abundance and recruitment patterns. Instead, stronger top‐down control and/or a lower density of host anemones in the MPA were potential factors for such patterns. Our results highlight the importance of dissimilarity in a marine environment as a factor that affects connectivity.