The invertebrate community of the Peak–Speedwell cave system,Derbyshire, England — pressures and considerations for conservation management

1. The freshwater ecology of cave ecosystems has been poorly studied when compared with surface (epigean) systems. Most subterranean communities are typified by low abundance and low diversity of fauna due to the absence of primary production and other readily available organic carbon sources. 2. The macroinvertebrate community within the inter‐connected Peak–Speedwell cave system in the English Peak District was examined over a 2‐year period. The communities found in the surface streams which supply recharge to the Speedwell Cavern stream, and the communities in the three springs which discharge water from the cave system, were also examined. 3. Changes in the community were strongly associated with seasonal variations and natural hydrological variability. Spatial patterns within the caves reflect differences in water sources (sinking streams or percolation water) and in the ability of the organisms to survive and move through subterranean environments. 4. The majority of taxa recorded within the caves were also found at the surface either in the sinking streams or in the springs. 5. Threats to cave geo‐ecosystems, including quarrying, agriculture, waste disposal, groundwater abstraction and tourism/recreation, are examined and discussed in relation to the management and conservation of subterranean environments. Copyright © 2000 John Wiley & Sons, Ltd.     

An experimental vaccine against Aeromonas hydrophila can induce protection in rainbow trout,Oncorhynchus mykiss (Walbaum)

A candidate vaccine against Aeromonas hydrophila in rainbow trout, Oncorhynchus mykiss, was developed using a bacterial lysate. To test the strength of protection, A. hydrophila challenge models were compared using injection into both the intraperitoneal (IP) cavity and the dorsal sinus (DS) with selected doses of live bacteria washed in saline or left untreated. Unlike the IP route, injection into the DS with either saline washed or unwashed cells resulted in consistent cumulative mortality and a dose response that could be used to establish a standard challenge having an LD₅₀ of approximately 3 × 10⁷ colony forming units per fish. Survivors of the challenge suffered significantly lower mortality upon re‐challenge than naïve fish, suggesting a high level of acquired resistance was elicited by infection. Passive immunization using serum from hyper‐immunized fish also resulted in significantly reduced mortality indicating protection can be transferred and that some portion of resistance may be antibody mediated. Vaccination of groups of rainbow trout with A. hydrophila lysate resulted in significant protection against a high challenge dose but only when injected along with Freund’s complete adjuvant. At a low challenge dose, mortality in all groups was low, but the bacterial lysate alone appeared to offer some protection.     

Effects of dietary Europium complex and Europium(III) on cultured pearl colour in the pearl oyster Pinctada martensii

In the present study, through a transmission experiment, the effects of europium complex and Eu³⁺ on the pearl colour in the pearl oyster Pinctada martensii were evaluated. Europium complex and europium salt were respectively enriched by dietary green algae platymonas subcordiformi, and their toxicity to algae were analysed by the 96‐h acute toxic experiment. Then, the green algae enriched europium complex and europium salt were respectively fed pearl oysters for 2 months, and the surface microstructures of cultured pearls were presented with scanning electron microscopy (SEM) and atomic force microscope(AFM). The results show that toxicity of europium complex to algae is much lower than Eu³⁺ from lowest no observable effect concentration LNOEC values and 96h‐EC₅₀ values and two compounds can modify pearl structure and optimize pearl colour from SEM and AFM images. Taken together, our results, for the first time, show that rare earth complex can improve the pearl quality. This study provides an innovative approach for additional investigation of the influence of rare earth elements on pearls.     

Meta‐analysis of post‐release fishing mortality in apex predatory pelagic sharks and white marlin

Robust assessments of the effects of fishing require accounting for components of fishing mortality, including post‐release fishing mortality (F_r). Random‐effects meta‐analysis synthesized F_r in seven pelagic shark species captured, tagged and released with 401 pop‐up satellite archival tags compiled from 33 studies and three gears (longline, purse‐seine, rod & reel). The majority of F_r outcomes occurred within days of release, and the summary effect size for F_r was 0.27 [95% CI: 0.19–0.36], ranging from a low pooled effect size of 0.17 for blue shark (Prionace glauca, Carcharhinidae) to 0.38 (silky shark, Carcharhinus falciformis, Carcharhinidae). F_r rates in blue shark were consistent over dissimilar spatial and temporal scales, and results from earlier meta‐analysis were replicated, which is the most powerful way to authenticate results. Condition at tagging was a strong predictor, and dichotomized survival outcomes in silky shark and no sex‐, size‐, location‐ or gear‐specific F_r rates were demonstrated. Meta‐analyses and sensitivity analyses indicated exposure to risk factors and conditions whilst caught on the gear probably had the largest explanatory effect on F_r, rather than stressors incurred during handling and release. Records from 549 tagged istiophorid billfishes (six species, three gears, 43 studies) demonstrated they are more robust to stressors sustained during capture, handling and release than pelagic sharks. Findings from previous meta‐analysis on F_r rates in white marlin (Kajikia albida, Istiophoridae) were replicated. Synthesized F_r rates enable prioritizing approaches to mitigate by‐catch fishing mortality, to improve the quality of stock and ecological risk assessments and to expand our knowledge of factors influencing trophic structure.     

Toxicity of the aquaculture pesticide cypermethrin to planktonic marine copepods

The acute and sublethal toxicity of cypermethrin, the active ingredient in the sea lice treatment formulation Excis^®, to non‐target planktonic marine copepods was determined. The comparative sensitivities of three life stages (nauplii, copepodites, adults) of four common marine copepods (Acartia clausi, Pseudocalanus elongatus, Temora longicornis and Oithona similis) were assessed in 48‐h exposures, followed by a recovery period in toxicant‐free sea water. The cyclopoid copepod, O. similis, was most affected by cypermethrin, with EC₅₀ values ranging from 0.14 to 0.24 μg L^?1 for nauplii and adults respectively. With the exception of T. longicornis nauplii, the calanoid copepods (A. clausi, P. elongatus and T. longicornis) responded similarly to cypermethrin. Overall, 48‐h EC₅₀ values ranged from 0.12 μg L^?1 (T. longicornis nauplii) to >5 μg L^?1 (P. elongatus adults). For all species, nauplii and copepodite EC₅₀ values were lower than those of the adults. The primary toxic effect, immobilization, was generally irreversible. A sublethal test with adult A. clausi females, involving pulse exposures over 4 days measured a significant increase in egg production at the higher concentrations (1.58 and 5 μg L^?1). Concentrations causing acute toxicity to planktonic copepods were lower than the recommended sea lice treatment concentration of 5 μg L^?1 cypermethrin, indicating the potential for toxic effects in the field. However, acute toxicity values were higher than the Environmental Quality Standard of 0.016 μg L^?1 for dispersing treatment plumes, suggesting that cypermethrin released to the marine environment following sea lice treatments is unlikely to affect adversely planktonic copepods.     

Effects of 2-phenoxyethanol on survival of normal juveniles and malformed juveniles having lordosis or nonfunctional swimbladders of European sea bass (Dicentrarchus labrax L., 1758)

The objectives of this study were to evaluate the effects of 2‐phenoxyethanol (2‐PE), which is an anaesthetic, on survival rates of normal juveniles and malformed juveniles having lordosis or nonfunctional swim bladders of European sea bass (Dicentrarchus labrax L., 1758) and to establish the LC₅₀ (the concentration lethal to 50% of test animals at concentrations of 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4 and 4.5 mL L⁻¹) and LT₅₀ (the time lethal to 50% of test animals after 10‐, 20‐, 30‐, 40‐, 50‐ and 60‐min time periods) of 2‐PE at 19±0.5°C, salinity 38 g L⁻¹, pH 7.4–7.8 and dissolved oxygen >8 mg L⁻¹. Between concentrations of 0.05 and 0.25 mL L⁻¹, 2‐PE did not cause any mortality or toxicity on normal, lordosis and nonfunctional swimbladder juveniles of sea bass during the 60‐min exposure period. On the other hand, significance in each group fish in their mortality rates between concentrations of 0.30 and 0.45 mL L⁻¹ was observed (P<0.05). The nonfunctional swimbladder juveniles showed lower LC₅₀ than normal and lordosis juveniles respectively. Also, nonfunctional swimbladders juveniles showed lower LT₅₀ than normal and lordosis juveniles respectively. At concentrations of 0.30, 0.35, 0.40 and 0.45 mL L⁻¹, induction times were found to be significantly different among the three groups (P<0.05). Recovery times were not found to be significantly different in two groups at concentrations of 0.30 and 0.40 mL L⁻¹ (P>0.05). The toxic effect of 2‐PE on sea bass juveniles increased depending on the exposure times (P<0.05). The most suitable concentrations of 2‐PE were 0.30–0.35 mL L⁻¹ between minutes 10 and 30, although the normal juveniles can resist to 0.45 mL L⁻¹ of 2‐PE concentration for 20 min. The 2‐PE showed toxicity in relation to the concentrations and exposure time combinations among the three groups in the order; nonfunctional swimbladder fish >lordosis fish >normal fish.     

Daily variation in short-term static toxicity of unionized ammonia in Litopenaeus vannamei (Boone) postlarvae

Ammonium toxicity of short‐duration alkaline events and their variability, as related to 1–30 day‐old postlarvae whiteleg shrimp Litopenaeus vannamei (Boone), was assessed by determining medium lethal concentration (LC₅₀) of total ammonium‐nitroen (TAN) and NH₃‐N to 4‐h exposures. Exploratory concentrations of TAN were tested at 30°C and pH 9, until mortality from 5% to 95% occurred between 0.9 and 18 mg N L^?1. To determine the daily variation of ammonium toxicity, 64 lots of 20 postlarvae were exposed to eight different ammonium concentrations (0, 0.9, 3, 6, 9, 12, 15 and 18 mg N L^?1), in two different environmental scenarios: α (pH 8, 26°C) and β (pH 9, 30°C). In environmental scenario α, ammonium concentrations up to 18 mg L^?1 pose no short‐term mortality risks for ages 1–30 days. In scenario β, mortality was recorded at all ages. The values of LC₅₀ (4 h) for different postlarvae ages have daily variability, ranging from a minimum of 2.54 to a maximum of 6.02 mg L^?1 of TAN (0.76 and 1.81 mg N L^?1 of NH₃‐N), for PL₃ and PL₁₉, respectively, with a logarithmic linear tendency to increase with age. Postlarvae mortality at 4 h and 3.0 mg N L^?1 TAN exposure was lower and less variable in ages greater than 19 days old.     

Relationships among invasive common carp,native fishes and physicochemical characteristics in upper Midwest (USA) lakes

Abstract – Common carp Cyprinus carpio is a widespread invasive species that, in high abundance, can impose numerous deleterious effects in aquatic ecosystems. Common carp increase turbidity and nutrient availability while reducing invertebrate prey resources and aquatic macrophytes, transforming shallow lakes from the clear‐ to turbid‐water state. However, potential effects of common carp on native fish communities have received limited attention. We evaluated the relationships among relative abundances of nine native fishes and common carp for 81 lakes in eastern South Dakota and their associated physicochemical characteristics. Inverse threshold relationships among relative abundances of native fishes and common carp were identified for black bullhead Ameiurus melas, black crappie Pomoxis nigromaculatus, bluegill Lepomis macrochirus, white bass Morone chrysops and northern pike Esox lucius, while marginally significant relationships were detected for largemouth bass Micropterus salmoides and smallmouth bass M. dolomieu. Lakes where common carp relative abundance exceeded 0.6 fish per net night had low abundance of native fishes, whereas lower abundance of common carp resulted in variable abundance of native fishes. Lakes with abundance of common carp surpassing 0.6 fish per net night were also characterised by larger surface areas and watersheds and impaired water quality (higher dissolved solids and chlorophyll a concentrations and lower secchi depth). Our results are consistent with the biotic‐abiotic constraining hypothesis that proposes biotic factors can regulate fish populations regardless of abiotic conditions. Thus, common carp abundance may need to be reduced and sustained below ecological thresholds to improve water quality and increase abundance of native fishes.     

Aphanizomenon flos-aquae,A Toxic Blue-Green Alga in Commercial Channel Catfish,Ictalurus punctatus,Ponds:

During the summers of 1990 and 1991 in the Lowcountry region of South Carolina, high mortality rates (50-90%) of channel catfish, Ictalurus punctatus, in production ponds were attributed to the toxic form of the blue-green alga (Cyanobacterium) Aphanizomenon flos-aquae. Toxicity varied with algal strain and/or stage in life history, and a simple bioassay was developed to account for the differential toxicity of algae within ponds. The bioassay required an intraperitoneal injection of a sonicated, 30X concentrate of algal cells that are injected into 8- to 20-g fish. Injection with 0.05 ml of concentrate from the toxic strains caused hyperactivity and paralysis in fish within 10 minutes and mortality within an hour. The endotoxin from A. flos-aquae (aphantoxin) was neutralized with the equivalent of 1.7 mg/L potassium permanganate beyond demand. In production ponds, an application of copper sulfate followed with potassium permanganate had variable success. Muddying the ponds had only limited success but appeared promising. Water and soil chemistry in this geographic area probably influenced the frequency of toxic A. flos-aquae blooms.     

First microsatellite data on Proteus anguinus reveal weak genetic structure between the caves of Postojna and Planina

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Assessment of magnesium chloride as an anaesthetic for adult sea urchins (Paracentrotus lividus): incidence on mortality and spawning

During this study different concentrations of magnesium chloride (MgCl₂) were tested on adult wild‐caught sea urchins (Paracentrotus lividus) immediately after their collection in the field in order to assess whether MgCl₂ can act as an anaesthetic during their transport and prevent unplanned spawning. Such accidental spawning is a stress response associated with transport of this species. The mortality and gonadal indices were recorded after a 1‐h submersion in different strength solutions of MgCl₂ (5, 20, 40, 80 and 100 mmol L⁻¹ MgCl₂), followed by 5 h of dry transport under two different temperatures (19 and 25 °C). The effective concentration of MgCl₂ was defined as one that does not induce mortality and gonad mass loss following sea urchin transport and laboratory conditioning. Treatment of sea urchins with 5 mmol L⁻¹ MgCl₂ prevented mortality and unplanned spawning; however, elevated concentrations of magnesium (40, 80 and 100 mM) were toxic to sea urchins, inducing a massive mortality and gonad mass decrease during the acclimatization period, essentially when sea urchins were transported under an elevated temperature (25 °C). It is concluded that MgCl₂ is a suitable non‐toxic anaesthetic, easily available for adult sea urchins (P. lividus) when it is used at its optimal anaesthetizing concentration.     

DEET (N,N‐diethyl‐m‐toluamide) Toxicity to Channel Catfish,Ictalurus punctatus,Sac Fry

The combination of open facilities, moisture, and warm weather during channel catfish, Ictalurus punctatus, spawning season causes mosquito‐infestation problems. A common solution to mosquito problems in hatcheries is to use mosquito repellents applied to exposed skin and clothing. DEET (N,N‐diethyl‐m‐toluamide) is the active ingredient in most personal insect repellents. We determined the 24‐h acute toxicity of DEET to channel catfish fry. The toxicity test consisted of 10 sac fry in three replications of six concentrations (range: 157–478 μL/L) and a control. In addition to toxicity testing, a trial was conducted to determine the amount of active ingredient dispensed from two different applicators: a pump sprayer and an aerosol can. The 24‐h lethal concentration (LC₁₀) was 274 ppm, and the 24‐h LC₅₀ was 345 ppm. The concentration required to kill 50% of the organisms was above the 100 ppm threshold to be considered practically non‐toxic. The pump sprayer (98.11% active ingredient) dispensed 113.3 ± 0.57 mg (mean ± SEM) active ingredient per pump. The aerosol can (30% active ingredient) dispensed 526.8 ± 6.71 mg (mean ± standard error mean [SEM]) active ingredient per second. In hatcheries where air movement by fans is not sufficient to control mosquitoes, using insect repellent products containing DEET should be safe.     

Decadal change in abundance of surface migratory myctophid fishes in the Kuroshio region from 1957 to 1994

Decadal change in abundance of surface migratory myctophid fishes was examined in the Kuroshio region of the western North Pacific for the 35 yr from 1957 to 1994 in relation to the Kuroshio regime shift, indicated by changes in its transport volume and sea surface temperature in the early 1970s. Each year, samples were collected from the 0‐ to 1‐m depth layer at night, from January to March, at 83 stations on average. Ten species belonging to five genera occurred. Juveniles [standard length (SL) ≤ 40 mm] and adults (SL > 40 mm) of each species were analysed. In juveniles, Myctophum asperum, M. nitidulum, Symbolophorus evermanni and Centrobranchus brevirostris accounted for 91.1% of the total catch (7419 individuals), while M. nitidulum contributed 82.4% of the total adult catch (494 individuals). The abundance of juvenile S. evermanni, C. brevirostris and M. nitidulum showed prominent peaks in 1971, together with adult M. nitidulum. These peaks corresponded to extraordinarily high zooplankton abundance in the Kuroshio region in 1971, suggesting high recruitment success and low adult mortality in surface migratory myctophids. Smaller changes in abundance in other years were species‐specific, and the fluctuation patterns were mainly explained by year‐to‐year fluctuations in the strength of the Kuroshio and the geographical distribution of each species, i.e. an increased Kuroshio flow volume resulted in an increase in tropical species and a decrease in temperate species, but no change in the pan‐Kuroshio species.     

Toxicity of Peracetic Acid to Fish: Variation among Species and Impact of Water Chemistry

There has been strong interest in the use of peracetic acid (PAA) in aquaculture as it can be used to disinfect water and hard surfaces and thereby eliminate or lower the burden of fish pathogens. Unfortunately, there has been little research on the toxicity of PAA to fish. Twelve species of fingerling fish that are important to aquaculture were exposed to PAA for 24 h in static toxicity bioassays in well water. These fish were: fathead minnow, Pimephales promelas; black‐nose crappie, Pomoxis nigromaculatus; bluegill, Lepomis macrochirus; blue tilapia, Oreochromis aureus; channel catfish, Ictalurus punctatus; golden shiner, Notemigonus crysoleucas; goldfish, Carassius auratus; grass carp, Ctenopharyngodon idella; largemouth bass, Micropterus salmoides; rainbow trout, Oncorhynchus mykiss; sunshine bass, Morone chrysops × M. saxatilis; and walleye, Sander vitreus. Median lethal concentration (LC₅₀) values were estimated with the trimmed Spearman–Karber method using nominal PAA concentrations. The mean 24‐h LC₅₀ values ranged from 2.8 to 9.3 mg/L PAA. Fathead minnow were very sensitive and blue tilapia were very tolerant to PAA exposure; LC₅₀ values of other species tested were within the range of 4.1–6.2 mg/L PAA. More importantly, the 24‐h no‐observed‐effect concentration (NOEC) ranged from 1.9 to 5.8 mg/L PAA; the NOEC would be considered as the safe range for culturists to investigate the use of PAA. Decreased alkalinity/hardness increased the toxicity of PAA, while a small increase of dissolved organic content had no effect on PAA toxicity. Results of the present study are important information on the safe application of PAA for the aquaculture industry.     

Long‐term stability of eelgrass fish assemblages in two highly developed coastal estuaries

Changes in fish assemblages were tracked in representative eelgrass (Zostera marina L.) beds within two estuaries on the urbanised coast of southern California, USA, San Diego Bay and Mission Bay, from 1987 to 2010. Assemblages were sampled twice yearly (spring and summer) at day and night using beach seines. Assemblage stability was examined over time along with changes in assemblage structure across time of day and season, including the influence of temporally variable abiotic variables. Only the occasionally occurring fish, those present in <70% of samples, in Mission Bay appeared to be shifting to a new assemblage. Although season and sampling time significantly affected assemblages, correlations with abiotic factors were low. Given the long history of urban development of these estuaries, community shifts may have occurred prior to the onset of sampling, giving the appearance of stability. Alternatively, eelgrass habitat may be providing a refuge from long‐term disturbances.     

Genetic diversity and relatedness estimates for captive barramundi (Lates calcarifer,Bloch) broodstock informs efforts to form a base population for selective breeding

Aquaculture of barramundi or Asian seabass (Lates calcarifer) is growing in both Australia and Southeast Asia and there is substantial interest to improve production efficiency through selective breeding. The establishment of a large and genetically diverse base population is a prerequisite for a sustainable and long‐term productive breeding program. Before selective breeding programs can begin for Australian barramundi it is important to assess the overall genetic diversity of current captive broodstock populations. To address this question, 407 captive barramundi broodstock from eight separate Australian broodstock populations were genotyped using 16 polymorphic microsatellite DNA markers. A Bayesian STRUCTURE analysis indicated that captive Australian broodstock are broadly divided into two genetic stocks. Multivariate analysis between broodstock individuals and pairwise F_ST between broodstock populations also supported the existence of two stocks. Comparisons with data obtained from natural stocks suggested that hatchery individuals were either sourced from the two stocks or represented an admixture between them. Genetic diversity was low within each broodstock population (allelic richness ranged from 2.67 to 3.42 and heterozygosity ranged from 0.453 to 0.537) and relatedness estimates within hatcheries were generally low (average r was equal to 0.141). We recommend sourcing captive individuals according to high levels of neutral genetic diversity and low levels of relatedness for the establishment of a base population. We also make recommendations about including genetically diverse wild individuals.     

Improving rearing performance in sea‐cage culture of Pacific bluefin tuna Thunnus orientalis juveniles (Temminck and Schlegel) using small sea cages

High levels of mortality occur in large net‐cage culture of Pacific bluefin tuna (PBF) Thunnus orientalis due to poor growth on commencement of sea‐cage culture obstructing the mass production of fingerlings. Therefore, we carried out this study to develop a countermeasure by using small sea cages (square with 13‐m sides). PBF juveniles were directly transferred to a 30‐m‐diameter cage (control) and compared them to fish transferred to small sea cages for 12 days before being merged into another 30‐m‐diameter cage. The survival rate, growth performance and potential factors increasing mortality were examined. The results of our study showed that survival rate in small sea cages was approximately 20% higher than that of the control. Poor growth also occurred in the small sea cages; however, its frequency and daily mortality rate were half those in the control. In addition, growth performance such as specific growth rate and weight gain of PBF juveniles in small sea cages significantly increased compared to the control. These results suggest that using small sea cages could be an effective countermeasure for poor growth, which may mitigate the high‐mortality conditions of current sea‐cage culture systems for PBF.     

Constrained by aliens,shifting landscape,or poor water quality? Factors affecting the persistence of amphibians in an urban pond network

1. Freshwater communities and especially pond‐breeding amphibians are extremely vulnerable to land‐use change, alien species introductions and the use of pesticides or other toxic chemicals, as reflected in their worldwide decline. Effective conservation and management of ponds requires a better understanding of the biotic and abiotic factors that shape diversity patterns and species distribution, especially in cases of habitat loss
2. The present study aimed to reveal and classify which pond and landscape characteristics are the most important determinants for the occurrence patterns of amphibian species as well as for the overall amphibian species richness in an urban pond network. To achieve this aim, 17 biotic and abiotic variables were measured for 61 ponds and the dataset was analysed by means of a machine‐learning approach, suitability indices and co‐occurrence modelling
3. The highest probability of Triturus macedonicus occurrence was found at fishless artificial and semi‐natural ponds. The persistence of Lissotriton graecus in ponds was predicted by high pond connectivity and the absence of fish reflecting the species dispersive potential. Pelophylax kurtmuelleri showed a higher probability of occurrence with increased pond connectivity and macrophyte cover.
4. Amphibian species richness was higher in fishless ponds with well‐oxygenated waters located in sites with a low to intermediate road density network. Ponds categorized as ‘average’ in terms of newt suitability were more frequently inhabited by fish than Triturus macedonicus. Alien fish species showed negative associations with both newt species, while both newt species showed a positive association between them.
5. The results support the view that conserving a greater number of water bodies with increased landscape connectivity and without any fish presence could provide amphibian species with alternative habitat choices, especially in sites with human pressure where pond stability is at stake owing to continuous landscape changes.