Modeling the coastal ecosystem complex: present situation and challenges

To enhance numerical modeling of the coastal ecosystem complex (CEC), we reviewed the CEC and related concepts along with the current coastal ecosystem model framework in this study. We identified two model implementation paths from the initial objectives to numerical models: specific model building, and the use of existing model frameworks. As the CEC is still at the conceptual stage, both paths are possible. Four important ecological features of CEC modeling (population connectivity, habitat heterogeneity, ontogeny of organisms, and trophic interactions) were also identified. Models for population connectivity, species distributions, life histories, and food webs were categorized using these features. We found that some previously established concepts (between–habitat interactions, coastal ecosystem mosaic, and seascape nursery) overlap with the CEC concept. Several existing integrated model frameworks were reviewed, focusing on their potential to simulate CEC processes. Building specific models for the CEC at the current conceptual stage will be challenging, and modification of existing models will be needed if they are to be used for CEC modeling. Habitat function, ontogenetic development in early life stages, and recruitment variability are important factors when modifying existing models for the development of CEC models. Although model complexity should become high to reproduce observed ecoclogical processes, an intermediate level of model ccomplexity is feasible to decrease parameter uncertainty in models for fisheries management.     

A new interspecific pear cultivar Yutaka: highly resistant to the two major diseases scab and black spot on Asian pears

Phytoplasma suspected symptoms of little leaf, flat stem, witches’ broom and leaf yellowing were recorded on the four legume species, cowpea (Vigna unguiculata (L.) Walp.), pigeon pea (Cajanus cajan (L.) Millsp.), lentil (Lens culinaris Medikus) and mung bean (Vigna radiata (L.) Wilczek) in the states of Delhi, Uttar Pradesh (UP) and Kerala from 2014 to 2016. DNA specific fragments of approximately 1.3 kb were amplified from symptomatic samples of cowpea, pigeon pea, lentil and mung bean in nested PCR assays by using two sets of universal phytoplasma nested specific primers P1/P7 followed by 3Far/3Rev. No DNA amplifications were observed in any of the non-symptomatic legume samples with same primer pairs. Pair wise sequence comparison, phylogeny and virtual RFLP analysis of 16S rDNA sequences of the four legume species confirmed the association of four different groups and subgroups of phytoplasmas in the present study. The mung bean witches’ broom at Delhi was identified to be associated with strain related to ‘Ca. P. aurantifolia’ (16SrII-D), pigeon pea little leaf at Faizabad, UP with strain related to ‘Ca. P. phoenicium’ (16SrIX-C), lentil witches’ broom at Faizabad, UP with ‘Ca. P. trifolii’ (16SrVI-D) and cow pea flat stem disease at Kerala with ‘Ca. P. cynodontis’ (16SrXIV-A). Association of ‘Ca. P. cynodontis' (16SrXIV-A) infecting cowpea, ‘Ca. P. trifolii’ (16SrVI-D) in lentil and phytoplasmas strain related to ‘Ca. P. phoenicium’ (16SrIX-C) infecting pigeon pea are the new reports to the world.     

Improved growth of flathead flounder Hippoglossoides dubius in hypoxic waters in Funka Bay,Japan

To identify the factors that influence the growth rate of flathead flounder Hippoglossoides dubius in Funka Bay, Japan, we studied temporal changes in the growth of this species and its prey from 1989 to 2012. The lowest growth rate of H. dubius was recorded in the 1995 year-class, which had experienced severe hypoxia between 1995 and 1997. However, the highest growth rate was recorded in the 2007 year-class, which had experienced hypoxia between 2009 and 2011. In 2000 and 2001, small-sized flounder (<200 mm TL) from the 1995 year-class were feeding on mysidaceans, whereas those from other year-classes fed on small Ophiura spp. (<9 mm in disc diameter) in 2009, 2011, and 2012. Small Ophiura spp. were more abundant in 2007 and 2011 than in 2002 and 2003. Successful recruitment of Ophiura spp. took place between 2007 and 2011 and cohorts from these years could tolerate hypoxia. This suggests that food availability improved under hypoxic conditions, which led to improved growth in small flounders. Large flounders (≥200 mm TL) from all year-classes fed on prickleback fishes (Stichaeidae) and walleye pollock Gadus chalcogrammus juveniles. The growth of large flounders was enhanced by an increase in the abundance of Stichaeidae fishes and G. chalcogrammus juveniles.     

Ontogeny of swim bladder inflation and caudal fin aspect ratio with reference to vertical distribution in Pacific bluefin tuna Thunnus orientalis larvae

It is necessary to understand the processes involved in sinking death in Pacific bluefin tuna Thunnus orientalis aquaculture in order to develop methods to prevent or minimize this problem. We observed the nighttime vertical distribution of Pacific bluefin tuna in the water column on 2–9 DAH and the morphological characteristics of the larvae, in order to clarify the processes involved in sinking death. A cuboid tank (height 300 cm) was used to measure vertical distribution. The number of larvae was counted in each of 4 regions in the observation tank: upper layer (water depth 0–100 cm), middle layer (100–200 cm), lower layer (200–300 cm), and bottom area. The distribution of larvae in these regions at 4 days after hatching was polarized to the upper layer and bottom area. Individuals with inflated swim bladders were observed in the upper layer 3 days after hatching. No larvae with inflated swim bladders were observed in the bottom area on any day after hatching. Total body length and caudal fin aspect ratio of larvae with both inflated and un-inflated swim bladders were greater in the upper layer than those of larvae in the bottom area. Larvae with un-inflated swim bladders that failed to develop sufficiently for swimming sank to the tank bottom and died. Swim bladder development and caudal fin swimming ability are strongly related to sinking death.     

Vertical behavior of juvenile yellowfin tuna Thunnus albacares in the southwestern part of Japan based on archival tagging

The behavior of juvenile yellowfin tuna Thunnus albacares in southwestern Japan was investigated using archival tag data from five fish (fork length 52.5–92 cm, days at liberty 26–280 days) released near the Nansei Islands (24–29°N, 122–130°E). Vertical behavior was classified into three patterns: “shallow” (≥50 % of daytime hours at depth of <50 m), “deep” (≥50 % of daytime hours at ≥100 m), and “intermediate” (other than “shallow” or “deep”). The pooled proportion of the number of days of each behavior was 29, 25 and 46 %, respectively. The proportion of “shallow” behavior increased with fish size. The proportion of time spent near the surface at nighttime increased in the colder season, when the thermal gradient was relatively small. Surface-oriented behavior (fish remained at a depth of <10 m for more than 10 min) occurred mainly during nighttime and between November and January. Dives exceeding 500 m were occasionally observed (0.02 day^?1), and one fish dived to 1230 m. The results of our study show that yellowfin tuna were typically distributed in the mixed layer or upper thermocline where the water temperature was close to the sea surface temperature and that the vertical behavior was variable.     

Blue stain fungi associated withTomicus piniperda (Coleoptera: Scolytidae) on Japanese red pine

A number of various species of blue-stain fungi were isolated fromTomicus piniperda adults at various stages of development, as well as from the galleries, pupal chambers and sapwood underneath galleries on Japanese red pine. This study was an attempt to identify the species, composition of blue-stain fungi associated withT. piniperda, the frequency of occurrence of the fungi, and their role in the sapwood-staining of Japanese red pine in Tsukuba City, central Japan. Among the seven species of blue-stain fungi isolated, an undescribed species ofOphiostoma together withO. minus were the dominant species and closely associated withT. piniperda. These two species occurred on newly emerging adults more frequently than the overwintered adults.Hormonema dematioides was also associated with the beetle, however, its frequency of occurrence from the emerged new adults was very low. Although the two other species,O. ips andGraphium sp. were also isolated from emerged beetles, the frequency of these fungi from gallery systems suggested that they were accidentally carried byT. piniperda. Leptographium wingfieldii, known to be associated with the beetle in Europe, was also isolated at a very low frequency and the fungus seemed not to be closely associated with the beetle.Ophiostoma sp. andO. minus appear to be the most important causes of blue-stain of Japanese red pine sapwood after infestation byT. piniperda.     

The use of machine learning to predict acute hepatopancreatic necrosis disease (AHPND) in shrimp farmed on the east coast of the Mekong Delta of Vietnam

Fisheries Science - Predicting the outbreak of disease is essential when managing shrimp farms. Acute hepatopancreatic necrosis disease (AHPND) caused by Vibrio parahaemolyticus is a serious...     

Changes to vertical thermoregulatory movements of juvenile bigeye tuna (Thunnus obesus) in the northwestern Pacific Ocean with time of day,seasonal ocean vertical thermal structure,and body size

Vertical movements related to the thermoregulation were investigated in 12 juvenile bigeye tuna (Thunnus obesus) in Japanese waters using archival tag data. Movements changed with time of day, season, and body size. During daytime, bigeye tuna descended to greater depths, presumably to feed in the deep scattering layer (DSL). Thereafter, they repeatedly ascended to shallower layers, suggesting attempts at behavioral thermoregulation, although the beginning of vertical thermoregulatory ascents might reflect a shift in DSL depth. By the end of such movement, the whole‐body heat‐transfer coefficient might decrease because, although the depth and ambient temperature of the upper layers did not change, the body temperature gradually decreased significantly just after ascent for thermoregulation. Seasonal patterns indicated that the vertical thermal structure of the ocean might influence this ascent behavior. For example, from January to May, bigeye tuna made fewer ascents to less shallow waters, suggesting that they respond to increasing depths of the mixed surface layer by reducing energy expenditure during vertical migration. In addition, as body size increased, fewer thermoregulatory ascents were required to maintain body temperature, and fish remained deeper for longer periods. Thus, vertical thermoregulatory movements might change with body size as bigeye tuna develop better endothermic and thermoregulatory abilities. We hypothesize that bigeye might also increase cold tolerance as they grow, possibly due to ontogenetic shifts in cardiac function.