Waters Off Research Articles

Differential population dynamics of a coastal porpoise correspond to the fishing effort in a large estuarine system

Abstract The finless porpoise (genus Neophocaena) is susceptible to fishery‐caused mortality, and its numbers are thought to be in decline across its entire range. However, population demographics have rarely been quantified for this genus, with a few exceptions of the narrow‐ridged form (Neophocaena asiaeorientalis) in waters off Japan, Korea, and in the Yangtze River of China, all of which show a drastic decline in recent decades. Similar analyses have not been performed for the Indo‐Pacific (known also as the wide‐ridged) finless porpoise (Neophocaena phocaenoides) that inhabits (sub‐)tropical waters; thus, reliable risk assessments are lacking. The demographic dynamics of the Indo‐Pacific finless porpoise in the Pearl River Delta (PRD) region were investigated by analysing 307 cases of beached carcasses that were recovered between 1996 and 2014. The mean instantaneous rate of increase r indicated a declining trend of 3.6% loss per annum during 1996–2005, and a subsequent recovering trend with 0.76% increase per annum during 2006–2014. The individual‐based Leslie matrix model constructed with the most up‐to‐date demographic parameters suggests that the conservation status of the finless porpoise in the PRD region corresponds to Near Threatened (NT) according to the International Union for the Conservation of Nature criterion A3. This temporal demographic change may be due to changes in fishing effort, which has been declining locally since the late 1990s. Although more quantitative evidence is needed, it is shown that regulated management of coastal fisheries can serve as an effective tool in securing the long‐term persistence of Indo‐Pacific finless porpoise in the PRD region, which likely applies also elsewhere in the genus/species' range where coastal fisheries overlap with the porpoise habitat. Results provide baseline ecological indicators that can facilitate further monitoring of the population status and trend.

A new species ofBemlosShoemaker, 1925 (Amphipoda: Aoridae) from deep water off Tanabe Bay, Japan, with a review of the deep-sea aorids and their adaptations to the deep sea

A new species of<i>Bemlos</i>Shoemaker, 1925 (Amphipoda: Aoridae) from deep water off Tanabe Bay, Japan, with a review of the deep-sea aorids and their adaptations to the deep sea

A first attempt to evaluate the age and growth of blue hake Antimora rostrata (Moridae, Gadiformes, Teleostei) from the Lazarev and Weddell seas (Antarctic)

AbstractFor the first time, the results of the study of the age and growth of blue hake Antimora rostrata in the waters of the Lazarev and Weddell seas (Antarctic) are presented. The longline catches were represented by fish from 42 to 69 cm in total length with weights between 420 and 2,900 g, and most individuals aged 25 to 27 years. A minimum age of 16 years was observed in a fish 47 cm long and weighing 450 g, while a maximum age of 35 years was recorded for an individual of 69 cm in length and 1,640 g in weight. The blue hake in the Lazarev and Weddell seas shows similar growth patterns to the fish from the Ross Sea and waters off Greenland.

Ecology of the Epiphytic Potentially Harmful Dinoflagellate Ostreopsis cf. ovata (Fukuyo) from Coastal Waters off Alexandria Egypt

Despite macroalgae epiphytes play an important role in algal habitats, available information from Alexandria coastal waters is scarce. To evaluate the role of environmental factors on the inventory of the ephyphytic Ostreopsis c.f ovata cells, its abundance on the thalli of 14 different macroalgae collected from two sites at Abou Qir rocky area was done on the basis of sampling carried out for one year. The annual maximum Ostreopsis cf. ovata cell abundance was observed in May (late-spring), reaching the maximum on the green macroalgae Ulva linza in July (mid- summer). Analysis of variance showed significant difference of abundance between seasons and hosts. Water temperature and NO2, NO3 and PO4 seem the major factor affecting on abundance of Ostreopsis c.f ovata. The present study documented the significant importance of Ulva sp. as the suitable host of O. ovata in Alexandria waters, in contrasting with others in the Mediterranean Sea that show O. ovata most often found on Phaeophyta and Rhodophyta.

Seasonal and interannual variability in crude fat content and condition factor of chub mackerel Scomber japonicus captured from waters off northeastern Japan during 2012–2017

Seasonal and interannual variability in crude fat content and condition factor of chub mackerel <i>Scomber japonicus</i> captured from waters off northeastern Japan during 2012–2017

Wettability of juvenile plumage as a major cause of mortality threatens endangered Barau's petrel

Seabirds spend most of their life at sea and have to possess a waterproof plumage to be able to sit on water for extended periods. We tracked juvenile Barau's petrels for the first time, when they leave their birth colony and found that half of the transmitters stopped soon after they first landed on the water off Réunion Island. We suspected from observation at sea that birds may have problems with the waterproofness of their plumage. Therefore during the next season we set up a simple protocol to assess waterproofness of the plumage of the birds just before they fledge. This protocol is based on the calculation of a wettability index expressed as the mass of water logged in the plumage after simulating the bird sitting on the sea surface. We found that at least one third of chicks ready to fledge gained more than 4 g of water in 20 s, indicating that plumage was not waterproof. Within a sample of birds having fledged and before reaching the sea surface, a similar proportion of birds had their plumage not waterproof. For the birds tracked, only those with an index indicating a waterproof plumage successfully dispersed after their first touch on the sea surface. We provide evidence of a possible major cause of mortality of juvenile seabirds that has not been described previously in wild seabirds, but could exist in other species. This issue may be a major cause of threat to the endangered Barau's petrel.

Assessment of Women and Children Vulnerability to Water Use in Low-Income Urban Area of Agbowo Community, Ibadan, Nigeria

One of the challenges of urbanization is the increasing vulnerability to quality water supply among households. Low-income urban households lack access to portable water and therefore have to supplement their limited supply with water from sources such as streams, rivers and wells. Whereas when water is available, the quantity is decreasing, and the quality is also compromised mainly due to high population growth accompanied by inadequate infrastructures and poor waste disposal practices. With children and women being most vulnerable to water challenges, the study examined the impacts of water shortages on women and children, investigated the effect of water supply on health outcome of children and looked into effect of water supply challenges on economic productivity of women in low-income urban area of Agbowo Community. The study collected both qualitative and quantitative data. Quantitative data was collected using KOBO collect software – an android-based application for collecting data while qualitative data was collected by employing Key Informant Interviews (KII). Statistical computations were carried out using Statistical Package for Social Science (SPSS) software. A confidence level of 99% was used and p-values ≤ 0.01 was considered statistically significant. The study noted that 74.4% of the respondents reported children and teenagers <18 years old are tasked with the responsibility of getting water for their household while 74% reported the occurrence of physical deformity as a result of the weight of the water. The study recommended that households should take the responsibility of getting water off children that are too tender and suggested special needs women such as pregnant women and nursing mothers should be put into consideration in development of water supply facilities.

Evaluation of the effects of otolith sampling strategies and ageing error on estimation of the age composition and growth curve for Pacific bluefin tuna Thunnus orientalis

The age composition of the catch and the growth curve of a stock are fundamentally important in fish stock assessment, but these estimates are subject to various sources of uncertainty. Using the Pacific bluefin tuna (Thunnus orientalis) fisheries in the waters off Taiwan as an example, we developed a Monte Carlo simulation model to evaluate the effects of four otolith sampling methods (random otolith sampling, ROS; fixed otolith sampling, FOS; proportional otolith sampling, POS; and reweighting otolith sampling, REW), and ageing error (bias and imprecision) on estimations of age composition and growth curves. The results indicated that FOS has the lowest sampling accuracy, POS performs the best and that ROS is a more efficient method with lower estimation error. For an imprecise reader, the centre (median) of multiple age reads is a useful method to obtain accurate and precise estimates. Ageing bias had greater effects on the estimation of age composition and growth parameters than ageing imprecision or the selection of otolith sampling methods. In most cases, 500 otoliths should be an adequate sample size and could be the guideline for the biological sampling program of the T. orientalis Catch Documentation Scheme.

Physical-biogeochemical interactions and potential effects on phytoplankton and Ulva prolifera in the coastal waters off Qingdao (Yellow Sea, China)

In recent years, the spectacular massive green tide of Ulva prolifera has become a recurrent phenomenon appearing every summer in the coastal waters off Qingdao (Yellow Sea, China), attracting the attention of scientists and local government. Based on multidisciplinary data collected during summer and winter, this study focuses on the hydrological characteristics and regional biogeochemical processes in coastal waters off Qingdao. The results show that the boundary of the Yellow Sea Cold Water Mass (YSCWM) can reach the Qingdao coastal region in summer and is locally raised to the upper layers to form coastal upwelling beyond tidal mixing and favorable wind. The regional summer upwelling off the Qingdao coast effectively enriches the nutrient concentrations in the upper water column and thus promotes growth of phytoplankton but reduces the dissolved oxygen (DO) concentration and pH value in the bottom. The regional summer upwelling off Qingdao coast may facilitate the growth and regional blooming of the U. prolifera that migrate to this region with the southerly wind. Additionally, the effects of the front on the aggregation of U. prolifera may be significant. In winter, the Yellow Sea Warm Current (YSWC) extends and spreads along the offshore region off the Subei Shoal towards the Qingdao coastal sea. This tongue-shaped warm water meets the cold coastal water off Qingdao, which leads to the formation of a physical front. As a consequence, remarkable fronts of nutrient and chlorophyll a (Chl a) also form between the shoreward warm water and the cold coastal water. This study increases the understanding of the interactions between the regional physical, chemical, and biological processes off the Qingdao coast.

Present distribution of common dolphin Delphinus delphis in French Mediterranean and adjacent waters as obtained from small boat surveys

Abstract Common dolphin distribution in the western Mediterranean is still poorly known, with the exception of the Alboran Sea. In French waters, the species occurrence is suspected to have strongly decreased during the 20th century. Small boat dedicated surveys from 1988 to 2012 were undertaken to describe common dolphin distribution in five regions of French waters and three southern regions of the western basin. A total survey effort of 38,561 km resulted in sightings of 25 common dolphin groups in the western basin. Common dolphins were rarely observed off the French continental coast, more frequently around Corsica, and were quite frequent in waters off western Sardinia. Their most favoured habitat was found to be in neritic or upper slope waters. The analysis of stranding records suggested that common dolphins were more abundant in French inshore waters prior to 1980. A major increase of pelagic fish landings occurred from the beginning of the 1960s in the western part of French waters. Local populations of common dolphins may have declined as a consequence of prey depletion.

Phylogeny and form in fishes: Genetic and morphometric characteristics of dragonets (Foetorepus sp.) do not align

AbstractMeasures of biodiversity are often hindered by a lack of methodological practices that distinguish cryptic or morphologically similar cohabiting species. This is particularly difficult for marine fishes where direct observations of the ecology and demography of populations are difficult. Dragonets (Foetorepus c.f. calauropomus) were collected as bycatch from research trawls deployed in waters off north‐eastern Tasmania, Australia. Morphometric and genetic analyses were conducted on the 43 specimens recovered. Sequence analysis of two mitochondrial loci distinguished three genetic clusters, each having levels of dissimilarity consistent with species‐level distinctions between other members of the Callionymidae. While clear morphological distinctions were observed between male and female fish, limited morphometric analyses could not differentiate between members of the three genetic groups. This finding highlights questions about the ability of genetically distinct but morphologically similar groups to occupy the same ecological niche, and points to additional and undescribed hidden biodiversity amongst cryptic species of fish.

Bioindication of Heavy-Metal Pollution in the Coastal Marine Waters of Russky Island (Peter the Great Bay, Sea of Japan)

The first assessment of the condition of coastal waters around Russky Island, Peter the Great Bay, in the vicinity of Vladivostok, has been made based on the data on concentrations of Fe, Zn, Cu, Cd, Pb, and Ni in the brown algae Sargassum miyabei and S. pallidum collected along the coast of the island in July and August 2016. It has been found that the concentrations of heavy metals in algae from waters off Russky Island mostly exceed their background levels in Sargassum algae from the northwestern Sea of Japan. On the southeastern side of the island, facing Ussuri Bay, which is distinguished by a rocky/bouldery coast and beds of S. pallidum, algae are characterized by lower concentrations of trace elements than those on the other sides.

The Recent Invasion of Cory's Shearwaters into Atlantic Canada

Abstract Calonectris diomedea (Cory's Shearwater) are observed in small numbers in Atlantic Canada every year. However, in 2016 and 2017, unusually high numbers were reported in both Nova Scotia and Newfoundland and Labrador, Canada. We used data from eBird and from standardized ship-based surveys to document the timing and magnitude of the increase. Results show that densities have been increasing in waters off Nova Scotia since 2007 and are now of similar magnitude to those observed on George's Bank in the late 1980s, which suggests that birds are targeting cooler, more productive waters on the Scotian Shelf during migration. Continued monitoring using a variety of survey techniques will help identify important marine areas for this trans-equatorial migrant, and identify potential threats as birds move into areas not previously explo ited.

Long-Term Monitoring of Scripps's Murrelet and Guadalupe Murrelet at San Clemente Island, California: Evaluation of Baseline Data in 2012–2016

San Clemente Island (SCI) supports one of the smallest Scripps's Murrelet (Synthliboramphus scrippsi; SCMU) colonies in the world, and perhaps the only colony of Guadalupe Murrelets (S. hypoleucus; GUMU) in California. In 2012–2016, the U.S. Navy sponsored development of a long-term murrelet monitoring program at SCI that utilized nocturnal spotlight surveys, night-lighting at-sea captures, and nest monitoring. Standardized spotlight survey transects were established in nearshore waters off breeding areas at Seal Cove and southeast SCI (SESCI). Baseline mean spotlight counts were 29 ± 15 murrelets (n = 31) at Seal Cove in 2013–2016 and 21 ± 10 murrelets (n = 15) at SESCI in 2014–2016. We banded 201 SCMU captured in congregations at Seal Cove (n = 158) and SESCI (n = 43); 12% of the SCMU from Seal Cove and 7% from SESCI were recaptured ≥1 year after banding. We also banded 21 GUMU at Seal Cove, but none were recaptured. Murrelet nests or eggs were found in 6 shoreline breeding “refuges” at Seal Cove and SESCI that were seldom if ever visited by island foxes (Urocyon littoralis clementae) and feral cats (Felis catus). Incubating SCMU were observed in 4 nest sites, but in 8 other sites only eggs or eggshells were found. Overall hatching success was very low (12%; n = 17 clutches) in 2012–2016, apparently due to intraspecific competition for limited nest crevices at Seal Cove and predation (or possibly abandonment and subsequent egg scavenging) by foxes or black rats (Rattus rattus) at SESCI. Using spotlight survey data, we estimated 115 murrelet pairs (range 79–208) at SCI, including 110 pairs (range 76–199) of SCMU and 5 pairs (range 3–9) of GUMU, although a GUMU nest has not yet been found. Power analyses of Seal Cove spotlight data indicated that surveys conducted over 9 nights per year for 20 years could reliably (power ≥ 0.90) detect minimum population changes of ±1.7% per annum. Additional efforts are needed to (1) confirm the breeding status of GUMU; (2) investigate alternative methods of rat control to increase hatching success in murrelet breeding refuges; and (3) enhance breeding habitats to reduce intraspecific competition for nest sites and increase the number of monitored nests.

Seasonal variation of phytoplankton growth and microzooplankton grazing in a tropical coastal water (off Kochi), Southwest coast of India

Phytoplankton growth and microzooplankton grazing in the coastal waters off Kochi, Southwest coast of India, were assessed during three seasons (Pre-Monsoon; Southwest Monsoon and Northeast Monsoon) using the dilution technique. Nutrients concentration in the study area was low during the Pre-Monsoon (PRM) compared to the Southwest Monsoon (SWM) and Northeast Monsoon (NEM) periods. Phytoplankton biomass (Chl. a) and growth rate were the highest during the SWM followed by the NEM. They were influenced mainly by the coastal upwelling and estuarine influx. Microzooplankton grazing rate varied from 0.11–0.27 day−1 and their grazing pressure on phytoplankton production varied from 26–80% day−1. The highest grazing pressure of microzooplankton on phytoplankton was found during the PRM, when nutrient concentration was low. It was found that ~80% of the daily phytoplankton production and 31% of their biomass were grazed by microzooplankton during the PRM. On the other hand, microzooplankton grazing on phytoplankton biomass and production were low (11% and 26%, respectively) during the nutrient-repleted SWM. Grazing experiments using size-fractionated phytoplankton showed that microzooplankton prefers nano size fraction of the phytoplankton community. This study presented a baseline information on microzooplankton grazing in the nearshore waters along the southwest coast of India during different seasonal hydrographical setting.

Tracing Different Freshwater Sources for Nutrients and Dissolved Organic Matter in Coastal Waters off Jeju Island Using Radon

In order to determine the origins of dissolved inorganic nutrients and dissolved organic matter in coastal waters off Jeju Island, Korea, we measured the concentrations of 222Rn, nutrients, fluorescent dissolved organic matter (FDOM), and dissolved organic carbon in coastal waters during September 2016 and October 2017. The lower salinity waters occurring in the southern coastal waters off Jeju (SCW) were characterized by higher nutrients and humic-like FDOM, while those in the western coastal waters off Jeju (WCW) showed no trend. A significant negative correlation between salinity and 222Rn in the SCW (r2 = 0.62, n = 7 for 2016; r2 = 0.56, n = 14 for 2017) indicates that freshwaters occurring in the SCW originate from fresh groundwater. However, depleted 222Rn activities in the fresh surface waters of the WCW indicate that those in the WCW originate mainly from the remote Changjiang diluted water. In general, the coastal ecosystem in the SCW is characterized by the dominance of brown seaweeds, and the WCW is by scleractinian corals. Our results imply that high nutrient concentrations in the SCW provide favorable conditions for the growth of seaweeds, while relatively low nutrient concentrations and high FDOM concentrations in the WCW provide favorable conditions for survival of corals.

Occurrence and Bycatch of Juvenile and Neonate Whale Sharks (Rhincodon typus) in Peruvian Waters1

In the eastern Pacific Ocean, whale sharks (Rhincodon typus) have mostly been studied off the Galapagos Islands, Ecuador, and Baja California, Mexico. Recently, satellite telemetry data revealed connectivity between whale sharks off the Galapagos Islands and Peru. Historic and some recent observations have reported rare occurrences of whale sharks in waters off northern Peru. However, no current detailed information on the occurrence of whale sharks in Peruvian waters has been published. In this study we compiled 27 records of whale sharks along the Peruvian coast as a first step to better understand their use of Peruvian waters. Northern Peru was identified as the main area of occurrence for whale sharks, and reports were more frequent during the austral summer (January to March) and spring (October to December). Moreover, presence of neonatal whale sharks reported in this study, in addition to that of previously satellite-tracked presumably pregnant females, suggests use of northern Peruvian waters as a pupping ground. Interactions occurred only with net fisheries and were evident in most (89%) of the records, but further studies should evaluate the extent of fisheries-shark interactions. As whale shark population numbers decline, effective conservation measures will require understanding of whale shark occurrences, and waters of northern Peru may play an important role in the species' biology and ecology. Systematic research is recommended to improve our understanding of habitat use of individuals present in Peruvian waters.

Phytoplankton and Bacterial Communities in South Harbour, Manila Bay, Philippines

In line with the ASEAN-India project “Extent of Transfer of Alien Invasive Organisms in South/Southeast Asia via Shipping”, phytoplankton and bacterial communities in the waters off South Harbour, Manila Bay were investigated. Sampling was done in July and August 2012 and in April and May 2013. A total of 67 phytoplankton species including 29 diatoms and 38 dinoflagellates were identified. Potentially toxic Pseudo-nitzschia spp. were among the diatoms found as well as dinoflagellates Alexandrium spp., and Gymnodinium spp. The diatom Skeletonema costatum appeared to be the dominant species in July and August 2012, whereas Chaetoceros spp. constituted over 85% of the total phytoplankton assemblage in April and May 2013. Mean bacterialabundance ranged from 9.53 x 102–3.18 x 105 cells/mL in July 2012. In addition, 93 bacterial isolates were identified using 16S rDNA, several of which belonged to the following phyla: Actinobacteria, Bacteriodetes, Firmicutes, and Proteobacteria; whereas, others were determined as uncultured bacterial clones. These results will serve as a valuable baseline for future studies on phytoplankton and bacterial community structure in Manila Bay.

FOOTFALL PATTERN OF A BOTTOM-WALKING CROCODILE (CROCODYLUS ACUTUS)

Abstract Drone footage of a large American crocodile bottom walking in shallow coastal water off Costa Rica was used to estimate oblique pace and stride lengths and pace angulations from autopodial touchdowns. The crocodile's pes stride lengths were longer but more variable than expected for an individual of comparable size high-walking on land, due in part to punting locomotion, but also to wave action moving the reptile's body. Pace angulations were also larger than expectations for a crocodile high walking on land. These features are also seen in fossil trackways, suggesting that trackways ascribed to “swimming” crocodylomorphs might better be characterized as made by bottom walking and punting reptiles.

Food habits of the blue shark, Prionace glauca (Linnaeus, 1758), in waters off northern Peru

Food habits of the blue shark, Prionace glauca (Linnaeus, 1758), in waters off northern Peru