Fluctuations of abundance and survival rate during the egg and larval stages of Japanese anchovy Engraulis japonicus in the Seto Inland Sea (1980–2007)

In order to understand the processes affecting early survival of the Japanese anchovy Engraulis japonicus population in the Seto Inland Sea, we examined the monthly fluctuations in the abundance and survival rates from eggs to recruits (15-day-old larvae, 13?mm in standard length fish, defined as 1-month-old fish) during their main spawning season from 1980 to 2007. The abundance of the yolksac larvae positively correlated with the abundance of eggs, but the abundance of recruits did not significantly correlate with the abundance of yolksac larvae. These results imply that the survival rate during the egg stage is relatively stable, but that the rate during the larval stage is variable. Of the three most recent decades (1980s, 1990s and 2000s), the abundance of recruits was highest in the 1980s. The decrease in the abundance of recruits after the 1990s can be considered to have occurred through a decline in survival rate during the larval stage because there were no significant differences in egg abundance, yolksac larval abundance, and survival rates during the egg stage in the three decades of the study period.     

The effects of the 1983 El Niño on Oregon's Coho (Oncorhynchus kisutch) and Chinook (O. tshawytscha) Salmon

The 1983 El Niño event off the Pacific Coast of North America resulted in increased adult mortality and decreased average size for Oregon's coho and chinook salmon. Actual return of adult coho salmon to the Oregon Production Area in 1983 was only 42% of the pre-season prediction. Coho smolts entering the ocean in the spring of 1983 also survived poorly, resulting in low adult returns again in 1984. Abundance of chinook stocks in southern Oregon was also reduced, as was abundance of Columbia River chinook stocks that show localized ocean distribution. Northerly migrating chinook stocks from the Columbia River showed little or no decline in abundance. The average weight of coho and chinook salmon landed in 1983 by Oregon's commercial troll fishery was the lowest recorded since statistics were first recorded in 1952. Comparison of the length-weight relationship for these fish indicated coho and chinook were in poorer condition in 1983 than in non-El Niño years. Because adult coho salmon returned to hatcheries at a smaller size, the fecundity (eggs per female) in 1983 was reduced from the 1978–1982 average by 24% at coastal hatcheries and by 27% at Columbia River hatcheries. The fecundity of chinook salmon was unchanged at most hatcheries.     

A scientometric mapping of research on Aeromonas infection in fish across the world (1998–2020)

Aeromonas spp are the most common devastating fish bacterial pathogens associated with a wide range of cultured freshwater fish resulting in mass mortality. The present study plots the Aeromonas research output in fish during 1998–2020 by means of the Web of Science (WoS) database. A total of 1944 publications were used for this investigation to evaluate the scientific productivity in this selected subject area. Global publication share, rank, and its development in terms of research and bibliometric indices such as overall citations, h-index, and average citation per paper were also analysed. China ranked first in terms of total publications among the most productive countries and accounted for 26.18% of the total publications. The network visualisation map revealed that the lead collaborating country was China; however, the collaboration between countries was found to be very less. Lokta’s law was noticed not to be valid for Aeromonas research. The study showed that the funding granted to the research investigations and their research productivity in terms of total publications were correlated positively. The results of the current study displayed the trend of “Aeromonas infection in fish” related research investigations published during 1998–2020. This study also highlighted the focused research areas on this topic on which the future areas of research can be determined by fellow researchers in this specific field. This study also suggests enhancing the research efforts on this bacterial pathogen which has the potential to implicate huge economic loss to the fish farming population in the world.

     

Simulation of copepod biomass by a prey–predator model in Hiuchi-nada,central part of the Seto Inland Sea: does copepod biomass affect the recruitment to the shirasu (Japanese larval anchovy <Emphasis Type="Italic">Engraulis japonicus</Emphasis>) fishery?

We have modeled the prey–predator dynamics between nutrients, phytoplankton, and copepods in Hiuchi-nada, central part of the Seto Inland Sea. The model parameters were estimated by stepwise regression using data sampled from 2001 to 2005. We re-created the fluctuations in copepod biomass in the spring–summer of 2001–2004 by model simulation and investigated the relationship between the re-created copepod biomass and anchovy Engraulis japonicus reproductive success rate in Hiuchi-nada. The anchovy reproductive success rate was proportional to the copepod biomass during the last 10 days of May, a period that immediately preceded anchovy recruitment. This relationship indicates that a possible key factor in the regulation of anchovy population levels is the fluctuation in abundance of the copepod assemblage and that the crucial period for anchovy recruitment in Hiuchi-nada would be the period just before anchovy recruitment to the shirasu (body length: approx. 20–35 mm) fishery. These results provide a potential framework for forecasting the anchovy recruitment level that is based on both larval abundance and survival rate as estimated from the biomass of copepods in the pre-recruitment period of anchovy.     

Study of food web structure and trophic level in the sea ponds of an optimized culture model (jellyfish–shellfish–fish–prawn)

The food sources of the main economic animals and trophic levels of biotic communities from an optimized culture model (Rhopilema–Sinonovacula constricta–Paralichthys olivaceus–Penaeus chinensis) in a sea water pond in Donggang, Liaoning province were studied using the stable carbon and nitrogen isotopes technique. The results indicated that the values of δ¹³C range from (?27.28 ± 0.35) ‰ to (?16.65 ± 0.20) ‰ and the values of δ¹⁵N range from (3.68 ± 0.23) ‰ to (13.91 ± 0.26) ‰, both of which exhibited significant fluctuations. The δ¹³C values of P. chinensis, Macrobrachium mipponensis and P. olivaceus were comparatively higher than those of other aquaculture animals, and the δ¹⁵N values of P. olivaceus was also comparatively higher. The contribution to the food sources of aquaculture animals (Rhopilema, S. constricta, P. olivaceus and P. chinensis) was analyzed by using the IsoSource software. The results indicated that fish meat had the greatest contribution to Rhopilema, S. constricta and P. chinensis; P. chinensis had the greatest contribution to P. olivaceus, followed by the M. mipponensis. The trophic level of the biotic communities under that optimized culture model in a sea water pond was 3.54, in which P. olivaceus was in the fourth level (3.54); P. chinensis, Synechogobius hasta, Ablennes anastomella, M. mipponensis, Ditrema temmincki Bleeker, Chelon haematocheilus were in the third trophic levels; Rhopilema, Engraulis japonius, S. constricta and zooplankton (1.00) in the second trophic levels, suspended matters (0.15) including phytoplankton, bacteria, humus, etc., were in the primary trophic levels.     

Recruitment of <Emphasis Type="Italic">Tapes philippinarum</Emphasis> in the Venice Lagoon (Italy) during 2002–2007

Currently, Tapes philippinarum, the Manila clam, is the primary fishery resource for about 1,000 fishermen and aquaculturists in the Venice Lagoon. The recruitment of this clam is a key component supporting shellfish culture industry that is almost completely dependent on the gathering of wild clam seed in nursery areas where the juveniles accrue at high densities as a consequence of favourable environmental conditions. The objective of the present study was to identify the areas optimal for the recruitment of T. philippinarum, herein referred to as nursery areas, and to evaluate the recruitment success each year for the period 2002–2007. Sampling was conducted with a hydraulic dredge at 25 stations, in at least three separate periods from April to September each year for 2002, 2003 and 2004, and at 15 stations for 2005, 2006 and 2007. The zero-year cohorts of this species were usually first detected in bottom samples in late spring (May and June). Some setting appears to occur throughout the summer. The peak of seed density, expressed as number of individuals retained on a 1-mm mesh screen per square metre of sampled substrate, was recorded in September. Measurable fluctuations in annual recruitment have been observed, with peak densities of juveniles in 2002 and 2003 (about 2,000/m²) and minimum densities in 2006 (about 44/m²). In the summer 2007, densities over 30,000/m² were found at the mouth of the River Brenta, immediately adjacent to the southern end of the Venice Lagoon. These intensive, multiyear surveys of this species furnish critical information on seasonal reproduction patterns and recruitment success, which is essential for the rational development of a local fishing master plan and for the formulation of a management strategy for sustainable utilisation of this shellfish resource in the Venice Lagoon.     

The potential for aquaculture of the bearded horse mussel (Modiolus barbatus) and Noah’s Ark shell (Arca noae) in southern Croatia

To assess the potential of the bearded horse mussel (Modiolus barbatus) and Noah’s Ark shell (Arca noae) for aquaculture in southern Croatia, we analyzed their survival and growth rates under two experimental conditions—suspended culture and on-bottom culture. Furthermore, we investigated feeding on zooplankton by these two species in suspended culture conditions and compared them with previously published results of their feeding on zooplankton in the natural benthic environment. Experimental studies were conducted in Mali Ston Bay (Adriatic Sea) from December 2009 to December 2010. Differences were observed in terms of survival of tagged M. barbatus and A. noae—specimens of M. barbatus exhibited much better survival rates both in suspended culture and in on-bottom cages than did A. noae. Growth of A. noae under both culture conditions was essentially negligible, while M. barbatus grew several times faster in suspended culture than on the bottom. Values for the growth constant K and L _inf for M. barbatus in suspended culture were 0.45 year^?1 and 55.9 mm, while corresponding values for on-bottom culture were 0.09 year^?1 and 58.6 mm, respectively. Zooplankters were present in the stomachs of 86.3 % of M. barbatus and 86.4 % of A. noae. Most abundant taxa were bivalve larvae followed by tintinnids, copepods, unidentified eggs and gastropod larvae. In conclusion, this study clearly shows that M. barbatus is a promising candidate for suspended aquaculture in southern Croatia.     

Mass spectrometry-assisted confirmation of the inability of dipeptidyl peptidase-4 to cleave goldfish peptide YY(1–36) and the lack of anorexigenic effects of peptide YY(3–36) in goldfish (<Emphasis Type="Italic">Carassius auratus</Emphasis>)

Dipeptidyl peptidase-4 (DPP4) is a serine protease of great interest because it has been shown to modulate the activity of several peptidergic factors including peptide YY (PYY) and glucagon-like peptide-1/2. While PYY(1–36) is orexigenic in mammals, PYY(3–36) recently garnered interest as a potent anorexigen. In silico phylogenetic analysis found that the DPP4 cleavage sites are absent in fish PYY sequences. However, no studies were conducted to show that indeed PYY(3–36) is not produced by DPP4 in fish. If DPP4 does not cleave PYY(1–36), is PYY(3–36) an anorexigen in fish? The objectives of this research were to (1) test whether DPP4 cleaves goldfish PYY(1–36) and (2) determine whether PYY(3–36) is an anorexigen in goldfish. First, we identified the highly conserved catalytic region of DPP4 in goldfish. Abundant expression of DPP4 mRNA was found within the gastrointestinal tract. We also report the first MALDI-MS cleavage analysis of DPP4 effects on PYY(1–36) in a non-mammalian vertebrate. Our novel results indicate that DPP4 is unable to cleave goldfish PYY(1–36) to PYY(3–36) in vitro. It also confirms a previously held hypothesis that DPP4 is unable to cleave fish PYY(1–36) that contains N-terminal proline–proline residues. PYY(3–36) had no effects on food intake of goldfish. The appetite inhibitory effects of intraperitoneal and intracerebroventricular injections of 10 ng/g body weight gfPYY(1–36) were abolished by coinjections of BIBP3226, a Y1 receptor antagonist. These results are significant because it shows the lack of generation of endogenous PYY(3–36) and its anorectic effects in goldfish.     

The relevance of preserving temporary ponds during drought: hydrological and vegetation changes over a 16-year period in the Doñana National Park (south-west Spain)

• 1. Although the Doñana National Park is given the highest degree of environmental protection in Spain, it is likely that groundwater discharge to several ponds within the Biological Reserve has been damaged by abstraction to a tourist resort located less than 1 km away.
• 2. Hydrological changes were monitored over 16 years (1 October 1989 to 30 September 2005) by recording the shallow water table of six temporary ponds at 1–8-week intervals, and the duration of pond wet phase (or hydroperiod) during each hydrological cycle.
• 3. The average rainfall for the study period was 563.2 mm, and included 6 wet, 5 moderate, and 5 dry years in a seemingly random sequence. The average rainy season extended from October until the end of March, while the dry season occupied the rest of the year.
• 4. The water table generally oscillated following this alternation of rainy and dry seasons, but this fluctuation was minimal during dry years, and even failed to occur at some ponds.
• 5. Since 1998/99, the average hydroperiod has shortened by 3 months at Charco del Toro pond, and by almost 2 months at Brezo pond, while the rest of the ponds exhibited a reduction of less than 1 month.
• 6. Vegetation changed in the ponds between May 1990 and 2005. Total plant cover increased (range of increase: 16–65%), and species richness decreased in all ponds (range of species loss: 4–18).
• 7. The reduction in the hydroperiod probably enhanced the growth of a few woody plants to the detriment of flooding-dependent species as the cover of Pinus pinea increased nearly fourfold at Brezo pond, while that of Scirpus lacustris was halved at Charco del Toro pond.
• 8. The pumping area for the nearby tourist resort should be relocated, and a specific management strategy should be developed in order to prevent further damage to the ponds.

Copyright © 2007 John Wiley & Sons, Ltd.     

Seasonal dynamics and yearly change in the abundance of metacercariae of <Emphasis Type="Italic">Parabucephalopsis parasiluri</Emphasis> (Trematoda: Bucephalidae) in the second intermediate host in the Uji–Yodo River,central Japan

An introduced pathogenic fish trematode, Parabucephalopsis parasiluri Wang, 1985 (Digenea: Bucephalidae), was studied to determine the seasonal fluctuation in its metacercariae abundance. The timing of the recruitment period of the metacercariae and the relationship between yearly fluctuation in metacercarial abundance and some environmental factors were also examined to develop an effective plan for disease control. Monthly changes in metacercarial abundance in the caudal fin of pale chub (Zacco platypus) and of the prevalence of the first intermediate host (golden mussel Limnoperna fortunei) suggest that P. parasiluri generally has an annual life cycle. The metacercarial abundance in chub increased when the water temperature fell below 7°C in winter, but the rapidity of the increase varied between 2007 and 2008. The fluctuations in the abundance of metacercariae in winter from 2001 to 2008 showed that mean flow rate and mean water level in January were negatively related to the infection level each year, and positively related to the mean water temperature. Based on these results, we propose a control plan for parabucephalopsiosis involving discharge control; that is, more than 50 m³/s (corresponding to 150 m³/s in the Yodo River) of water should be flushed from upstream dams for a period of at least one week starting on the day when the water temperature falls below 7°C.     

Quantifying current and future risks of invasiveness of non-native aquatic species in highly urbanised estuarine ecosystems—A case study of the River Neretva Estuary (Eastern Adriatic Sea: Croatia and Bosnia–Herzegovina)

Biological invasions are a major driver of global environmental change as invasive non-native species can exert severe environmental impacts on invaded ecosystems. Estuaries are especially vulnerable to biological invasions, which in highly urbanised areas are further facilitated by introduction pathways linked to commercial activities. This study provides a risk screening of non-native invasive species for the highly urbanised River Neretva Estuary (Eastern Adriatic Sea: Croatia and Bosnia–Herzegovina). In total, 12 species of non-native aquatic organisms were identified and screened for their invasiveness with the Aquatic Species Invasiveness Screening Kit. Of these species, eight were classified as carrying a high risk of invasiveness under current climate conditions and nine under future climate conditions. Amongst the high-risk species, blue crab Callinectes sapidus has already caused impacts in the risk assessment area, where it also represents an important economic resource. The “horizon” species Pacific oyster Crassostrea gigas and Manila clam Ruditapes philippinarum also carried a high risk of invasiveness, which for the latter species applied under predicted global warming. The present findings will contribute towards preventative management and control measures for the conservation of the natural ecosystem of the River Neretva Estuary whilst accounting for aquatic farming demands.     

Oxygen consumption in trilobite larvae of the mangrove horseshoe crab (Carcinoscorpius rotundicauda; Latreille, 1802): effect of temperature,salinity, pH,and light–dark cycle

A set of feeding trials was carried out for different microalgal species and processed diets for the culture of the New Zealand pipi, Paphies australis. Five microalgal species (Isochrysis galbana clone T-ISO, Pavlova lutheri, Tetraselmis suecica, Chaetoceros muelleri, and Thalassiora pseudonana clone 3H) and three formulated diets (baker's yeast, wheat flour, and corn flour) were fed to spat, juvenile, and adult pipi for 21 days. Unfed pipi were used in the control group. The spat and juvenile pipi showed a major shell increase with I. galbana while the greatest wet weight increase was obtained with P. lutheri. The shells of adult pipi grew better with corn flour, and the P. lutheri-fed group obtained the greatest wet weight. Results of proximate analysis in adult pipi revealed that proteins and lipids were accumulated in the tissue for all fed groups, while carbohydrate levels were depleted in all treatments including the control group. It is suggested that the gonads have developed during the experiment.     

A comparison of the habitat value of sub-tidal and floating oyster (<Emphasis Type="Italic">Crassostrea virginica</Emphasis>) aquaculture gear with a created reef in Delaware’s Inland Bays,USA

The culture of the Eastern oyster (Crassostrea virginica) in containment gear has become a viable component of restoration programs in many states on the East Coast of the United States, and it has been suggested that these operations may provide many of the same ecological services as natural or restored reefs. Our two-part study comparing the diversity and abundance in macro-epifaunal communities associated with a sub-tidal-created oyster reef and ‘modified rack and bag’ cage system (Part I) and floating oyster cages for restoration (Part II) occurred over the summer and fall of 2006 and 2007, respectively. In Part I, a greater total abundance and species richness (P < 0.05) was found to be associated with the cages, but greater evenness (P < 0.05) was found on the reef. No significant difference (P > 0.05) was found in species diversity according to Simpson’s index by habitat type, but it was significant (P < 0.05) by month. These samples were dominated by naked goby (Gobisoma bosc) and Atlantic mud crab (Panopeus herbstii). Spaghetti worm (Ampharetidae, P < 0.01), sheepshead (Archosargus probatocephalus, P < 0.01), blue crab (Callinectes sapidus, P < 0.01), grey snapper (Lutjanus griseus, P < 0.05), gag grouper (Mycteroperca microlepis, P < 0.01), and Atlantic oyster drill (Urosalpinx cinera, P < 0.05) were unique to the cages, while the skilletfish (Gobiesox strumosus) was unique to the reef. Part II revealed that the floating cages supported 13 species of fish and invertebrates, although no significant differences in species richness, evenness, or diversity were found by month or by bay area (P > 0.05). These results suggest that created reefs in conjunction with ‘rack and bag’ cage systems, as well as floating cage systems, support ecologically and economically important macro-epifauna, even at very small scales.