Regional variation in larval retention and dispersal drives recruitment patterns in a temperate reef fish

Although there is wide appreciation for the influence of variable larval transport on recruitment, few studies have investigated the relationship between recruitment intensity and the origin(s) of recruits. We evaluate this relationship for the common triplefin Forsterygion lapillum in Wellington Harbour (a semi-enclosed bay) and the adjacent open coast of North Island, New Zealand. As the harbour is productive, with many F. lapillum adults, we predicted the harbour would be an important source of recruitment for both regions. We estimated larval origins and dispersal histories using embryonic and larval otolith chemistry, respectively, with differences in otolith elemental composition consistent with birth and/or development in either harbour or open ocean waters. In the harbour, recruitment was greatest when locally spawned larvae were retained. Although large recruitment pulses to the open coast were comprised mostly of larvae originating from the open coast, 72 % of all recruits to the south coast were actually spawned in the harbour. Dispersal of larvae from the harbour was frequent, but in low numbers, and was unrelated to opportunities for transport from the harbour. Given recent evidence for differences in larval growth between regions, we suggest that (1) faster larval growth combined with nearshore larval distributions result in high recruitment to the harbour and moderate, but demograph-ically important, dispersal from the harbour to the open coast. In contrast, we suggest that (2) the combination of strong tidal currents in Cook Strait and slower larval growth result in lower recruitment and greater transport of larvae among open coast populations. The mechanisms that underlie such context-dependent dispersal have important implications for patterns of connectivity. © Inter-Research 2010.

Regional variation in larval retention and dispersal drives recruitment patterns in a temperate reef fish

Although there is wide appreciation for the influence of variable larval transport on recruitment, few studies have investigated the relationship between recruitment intensity and the origin(s) of recruits. We evaluate this relationship for the common triplefin Forsterygion lapillum in Wellington Harbour (a semi-enclosed bay) and the adjacent open coast of North Island, New Zealand. As the harbour is productive, with many F. lapillum adults, we predicted the harbour would be an important source of recruitment for both regions. We estimated larval origins and dispersal histories using embryonic and larval otolith chemistry, respectively, with differences in otolith elemental composition consistent with birth and/or development in either harbour or open ocean waters. In the harbour, recruitment was greatest when locally spawned larvae were retained. Although large recruitment pulses to the open coast were comprised mostly of larvae originating from the open coast, 72 % of all recruits to the south coast were actually spawned in the harbour. Dispersal of larvae from the harbour was frequent, but in low numbers, and was unrelated to opportunities for transport from the harbour. Given recent evidence for differences in larval growth between regions, we suggest that (1) faster larval growth combined with nearshore larval distributions result in high recruitment to the harbour and moderate, but demograph-ically important, dispersal from the harbour to the open coast. In contrast, we suggest that (2) the combination of strong tidal currents in Cook Strait and slower larval growth result in lower recruitment and greater transport of larvae among open coast populations. The mechanisms that underlie such context-dependent dispersal have important implications for patterns of connectivity. © Inter-Research 2010.

Limpet disturbance effects on barnacle recruitment are related to recruitment intensity but not recruit size

Intertidal limpets are important grazers along rocky coastlines worldwide that not only control algae but also influence invertebrates such as common barnacles. For instance, grazing limpets ingest settling barnacle cyprid larvae (hereafter cyprids) and push cyprids and barnacle recruits off the substrate. Such limpet disturbance effects (LDEs) can limit barnacle recruitment, a key demographic variable affecting barnacle population establishment and persistence. In this study, we examined limpet (Lottia cassis) disturbance to barnacle (Chthamalus dalli, Balanus glandula) recruitment on the Pacific coast of Hokkaido, Japan, as information on limpet-barnacle interactions from this region is missing. We investigated, for the first time, whether barnacle size and recruitment intensity influence LDEs on barnacle recruitment. Small barnacles may be less susceptible to LDEs than larger barnacles, because small size may reduce the propbability of limpet disturbance. Moreover, recruitment intensity can influence LDEs, as high recruitment can compensate for LDEs on barnacle recruitment density. In Hokkaido, C. dalli cyprids are smaller than B. glandula cyprids, and C. dalli recruitment is higher than B. glandula recruitment. Thus, we hypothesized that LDEs on C. dalli recruitment would be weaker than those on B. glandula recruitment. To test our hypothesis, we conducted a field experiment during which we manipulated limpet presence/absence on the interior surfaces of ring-shaped cages. After four weeks, we measured barnacle recruitment and recruit size on the interior surfaces of the cages and found negative LDEs on C. dalli and B. glandula recruitment and recruit size. As hypothesized, the LDEs on C. dalli recruitment were weaker than the LDEs on B. glandula recruitment. Additionally, C. dalli recruits were smaller than B. glandula recruits. However, the LDEs on C. dalli recruit size were as strong as the LDEs on B. glandula recruit size, indicating that the smaller C. dalli recruits are not less susceptible to LDEs than B. glandula recruits. Since C. dalli recruitment was higher than B. glandula recruitment, we propose that the higher C. dalli recruitment compensated for the LDEs on C. dalli recruitment. Our findings indicate that the detected differences in LDEs on barnacle recruitment are related to barnacle recruitment intensity but not recruit size.

Upwelling Bays: How Coastal Upwelling Controls Circulation, Habitat, and Productivity in Bays

Bays in coastal upwelling regions are physically driven and biochemically fueled by their interaction with open coastal waters. Wind-driven flow over the shelf imposes a circulation in the bay, which is also influenced by local wind stress and thermal bay–ocean density differences. Three types of bays are recognized based on the degree of exposure to coastal currents and winds (wide-open bays, square bays, and elongated bays), and the characteristic circulation and stratification patterns of each type are described. Retention of upwelled waters in bays allows for dense phytoplankton blooms that support productive bay ecosystems. Retention is also important for the accumulation of larvae, which accounts for high recruitment in bays. In addition, bays are coupled to the shelf ecosystem through export of plankton-rich waters during relaxation events. Ocean acidification and deoxygenation are a concern in bays because local extrema can develop beneath strong stratification.

Population study and habitat preferences of Pinang Jawa (Pinanga javana) in Mt. Slamet, Central Java, Indonesia

Zulkarnaen RN, Nisyawati, Witono JR. 2019. Population study and habitat preferences of Pinang Jawa (Pinanga javana) in Mt. Slamet, Central Java, Indonesia. Biodiversitas 20: 712-718. Conservation effort of Pinang Jawa is hampered due to lack of information on its ecology and population biology. The species is an endemic palm species to Java. The study aimed to assess the population study and habitat preference of Pinang Jawa in Mt. Slamet, Central Java. The research design used a purposive sampling method with a plot measuring 10x10 m. The observation plot was successfully made with a total of 183 plots. The result showed that the population was dominated by adult palm (mature) with the number of 1023 individuals on the southern slope of Mt. Slamet. Individuals growth dominated in hill slope. Population structure was dominated by individuals with stem heights of 6.1-8.1 m and stem diameters of 7-8.9 cm. The stem height and stem diameter class distribution showed that high mortality rate occurs in the seedlings stage class, although this stage should be high recruitment due to the seed production is perennial continuously. Predators were identified as the main threat for seedlings of Pinang Jawa. The result of statistical analysis clearly provides reveals that abiotic factors in which influencing the density of Pinang Jawa was slope, litter thickness, and crown cover.

Survival and recruitment in the population ecology of the endangered Bombina pachypus (Amphibia: Anura)

Global amphibian decline is a subject of great conservation concern, yet often basic demographic information is absent, which prevents the understanding of population trends and the planning of effective conservation management. We analysed capture-mark-recapture data from six populations of the endangered Bombina pachypus in order to understand the relative contribution of survival and recruitment to population growth, and to assess if any differences exist among populations in terms of their population dynamics. We found that survival was rather high and generally constant among sites, and recruitment was low, with the exception of two single years at one site. Population growth depended on survival on all sites, except the years following high recruitment at one site. Annual population size was generally lower than 30 individuals, but in one site it was estimated to be larger than 50. Our findings suggest that juvenile survival is more important for population dynamics than recruitment from the larval to the juvenile stage. We also suggest that the low recruitment rates we recorded was a result of juvenile dispersal, and that when populations exhibited high recruitment it was due to occasional successful migration or local recruitment. This pattern could represent a way to counterbalance the risk of inbreeding in populations composed of few individuals, a common characteristic of populations of B. pachypus. Finally, we suggest that conservation measures for B. pachypus should be planned at the landscape scale, and should not be limited solely to the breeding site and its close surroundings.

High turnover drives prolonged persistence of influenza in managed pig herds

Pigs have long been hypothesized to play a central role in the emergence of novel human influenza A virus (IAV) strains, by serving as mixing vessels for mammalian and avian variants. However, the key issue of viral persistence in swine populations at different scales is ill understood. We address this gap using epidemiological models calibrated against seroprevalence data from Dutch finishing pigs to estimate the ‘critical herd size’ (CHS) for IAV persistence. We then examine the viral phylogenetic evidence for persistence by comparing human and swine IAV. Models suggest a CHS of approximately 3000 pigs above which influenza was likely to persist, i.e. orders of magnitude lower than persistence thresholds for IAV and other acute viruses in humans. At national and regional scales, we found much stronger empirical signatures of prolonged persistence of IAV in swine compared with human populations. These striking levels of persistence in small populations are driven by the high recruitment rate of susceptible piglets, and have significant implications for management of swine and for overall patterns of genetic diversity of IAV.