Impact of fish and pearl farming on the benthic environments in Gokasho Bay: Evaluation from seasonal fluctuations of the macrobenthos

ABSTRACT: In order to clarify the influence of mariculture on the benthic fauna, samples of the macrobenthos were collected from Gokasho Bay, where intensive fish culture and pearl oyster culture have been carried out. Monthly samples collected from the fish farm and pearl farm sites during June 1995 to July 1996 revealed that the community structure of the two sites showed distinct differences with seasonal fluctuations. At the fish farm site, azoic conditions were found from July to November; after December, the diversity increased markedly through successive recruitments of small-sized species such as the polychaetes Capitella sp. and Pseudopolydora paucibranchiata , and the amphipods Aoroides spp.; macrofaunal density, biomass and species richness peaked from March to April. At the pearl farm site, a higher diversity, including larger-sized species, and no clear seasonal fluctuations in abundance was found, and the community structure was similar to that at the control site. These results show the large impact by fish farming on the macrofauna, whereas pearl farming causes less effect on the benthic fauna. It is suggested that the difference in the level of organic input between the two sites results in the differences in the dissolved oxygen content of the bottom water, sulfide content of the sediments and, subsequently, the macrobenthic assemblages.     

Repeated reaching of the harmful algal bloom of Karenia spp. around the Pacific shoreline of Kushiro,eastern Hokkaido,Japan, during autumn 2021

Unprecedented large-scale algal blooms were observed during autumn 2021 around the Katsurakoi fishing port, Kushiro, eastern Hokkaido, Japan. Monitoring of shoreline water showed that chlorophyll a (Chl a) concentrations and the cell density of Karenia spp., dominated by Karenia selliformis, repeatedly increased synchronously between September and November 2021. These increases were associated with a southerly wind-driven current, which transported offshore water on the shelf towards the shoreline at the sea surface. The blooms were prolonged as a result of algal accumulation in the semi-closed fishing port. The maximum Chl a concentration and cell density exceeded 50 µg Chl a/L and 10⁴ cells/mL, respectively. During the autumn bloom of Karenia spp., the nitrate?+?nitrite and phosphate concentrations in the water were lower than those in 2019 and 2020, and the silicate concentration was comparable. The ammonium concentration during the bloom was notably higher than before the bloom period, reaching 15 µM. Mass mortality of several fish species and echinoderms that were cultured using rearing water intake from the same shoreline occurred synchronously with the increase in Karenia spp.

     

The fate of organic matter derived from small-scale fish cage aquaculture in coastal waters of Sulawesi and Sumatra, Indonesia

To determine the fate of organic matter derived from fish cage aquaculture, carbon and nutrient cycling processes in waters and sediments, and water circulation, were examined at two fish cage farms of different size and utilizing different food types, on Sulawesi and Sumatra islands, Indonesia. Mass balance models of C, N and P were constructed to assess the pathways of waste utilization and dispersal. At the smaller farm in Sulawesi (64.5 m² cage area; 3 t annual net production) using pelleted food, there was proportionally less waste (≈ 40% of total C input) than at the larger Sumatran farm (2432 m² cage area; 9 t annual net production) using trash fish (≈ 70% of total C input) as food. At the small farm, the mass balance and hydrographic models indicated a maximum dispersal area of 1180 m², equivalent to 18 times the farm area. Within this area, 30% of total organic matter input (farm waste + fixed phytoplankton carbon) was buried in sediments with 30% mineralized in the water-column and 40% mineralized in the seabed. At the larger Sumatran farm, the models indicated a maximum dispersal area of 29  220 m², roughly 12 times the farm area. Within this area, 30% of total organic matter input (farm waste + natural pelagic input) was buried in sediments with 50% mineralized in the water-column and 20% mineralized on the seabed. There was some evidence of benthic enrichment at both farms, mostly as enhanced dissolved nutrient release, but sulfate reduction accounted for < 25% of total C flux, and denitrification/ammonium oxidation accounted for only 4–17% of N lost from sediments. There was no clear evidence of impact with distance from the cages at either farm. Phytoplankton gross primary production accounted for 60–77% of the total organic input to the receiving environment, suggesting that the relative importance of fish cage wastes must be assessed against natural inputs of organic matter.     

Histopathological studies on Vibrio harveyi– infected tiger puffer,Takifugu rubripes (Temminck et Schlegel), cultured in Japan

Vibrio harveyi infection occurred with a moderate mortality in tiger puffer, Takifugu rubripes (Temminck et Schlegel), in autumn 2007, at a mariculture farm in western Japan. The diseased fish showed nodular lesions in the branchial chamber and the inner surface of the operculum. Histopathologically, the lesions comprised granulation tissue containing many suppurative foci allowing propagation of the bacteria and granuloma encapsulating abscesses with a decrease in bacteria. The bacteria were disseminated in visceral organs including the spleen, kidney, liver, and myocardium, resulting in the formation of granulomatous lesions. Two groups of tiger puffer juveniles were artificially infected by an intramuscular injection with an isolate (1.0_10⁸ CFU/fish). During the experimental period, 20% mortality occurred within 4–6 days post‐infection (d.p.i). The fish sampled on 4 d.p.i showed abscesses in the lateral musculature at the injection site. The fish sampled 5 d.p.i. displayed the production of granulation tissue containing many suppurative foci, which replaced the necrotic dermis and lateral musculature. Surviving fish (15 d.p.i.) had granulomatous lesions in the lateral musculature at the injection site. Pyogranulomatosis is pathognomonic in V. harveyi infection of tiger puffer.     

Quantitation of inert feed ingestion in larval silver sea bream (Sparus sarba) using auto-fluorescence of alginate-based microparticulate diets

The ingestion of an inert feed as a sole food source was investigated in larval silver sea bream (Sparus sarba) fed an alginate-based microparticulate diet. Using the auto-fluorescent properties of pigments associated with the alginate base, ingestion and gut content were investigated over a 6 h experimental period in fed and unfed larvae. By extracting and measuring chlorophyll a (Chl a) and phaeopigment content of feeding larval fish and relating this to standardized Chl a and phaeopigment content of the diet, relative to diet weight, it was determined that individual fed 7-day old larvae had a maximum gut content of 1.05±0.09 g diet while 14-day old fed fish had a maximum gut content of 3.17±0.90 g diet. On average, the gut content of 14-day old fish was 2.89 times greater than the gut content of 7-day old fish. The dry weight of larval sea bream increased from 43±4.2 g at day 7 to 134.3±20.4 g at day 14 indicating that growth of fish fed this inert feed was substantial. Gut pigment dynamics suggested that Chl a was degraded to phaeopigments by 7-day but not 14-day old larvae and the individual gut dietary content varied considerably in 14-day old fish. The maximum Chl a and phaeopigment content in larval sea bream was 0.4 ng ind^–1 and 0.55 ng ind^–1 for 7-day old fish and 1.54 ng ind^–1 and 2.81 ng ind^–1 for 14-day old fish respectively. The present method may potentially allow simple and direct assessment of larval fish feed ingestion in both an experimental and commercial setting.     

Suspended culture of the sea cucumber Apostichopus japonicus below a Pacific oyster raft – potential for integrated multi‐trophic aquaculture

To discuss the possibility of co‐culturing Pacific oyster with the sea cucumber Apostichopus japonicus, a field experiment was conducted in an oyster farm. Apostichopus japonicus juveniles (mean wet weight, 0.08 g) were cultured below an oyster raft and at a control station for 216 days, and the wet weight and stable isotope ratios (δ¹³C, δ¹⁵N) were analysed together with settling organic matter (OM) collected using sediment traps. All sea cucumbers cultured below the raft survived (survival rate, 100%), while at the control station one individual disappeared (96%). During 216 days, the juveniles at the oyster and control stations grew to a mean weight of 5.5 and 2.6 g, attaining respective specific growth rates of 2.0% and 1.6% (paired t‐test, P < 0.001). Settlement rates of carbon and nitrogen at the oyster station were ~5 times larger than those at the control station. The stable isotope analysis showed that settling OM at both stations originated from coastal phytoplankton and that phytoplankton represented the primary food source for A. japonicus. The rapid growth of A. japonicus at the oyster station was concluded to be due to the abundant supply of oyster biodeposits, which could be ingested by this species.     

Pigment deposition and in vitro screening of natural pigment sources for enhancing pigmentation in male Siamese fighting fish (Betta splendens Regan, 1910)

Distribution in pigment deposition was studied in male Siamese fighting fish (Betta splendens Regan, 1910) of solid Blue and solid Red phenotypes. Growths were similar, and also indicated by similar activity ratio of trypsin to chymotrypsin. Growth strategy was different at maturing stage, whereas trypsin expression decreased in solid Blue while chymotrypsin expression decreased in solid Red (P ≤ 0.05). Ranking of total pigment contents was muscle > skin > caudal fin > anal fin > dorsal fin > pelvic fin > pectoral fin. Immature fish had similar total contents and concentrations of pigments, except solid Blue had higher total contents in dorsal fin than solid Red. At maturing stage, solid Blue showed higher total pigment contents than solid Red due to higher contents in the fins. Solid blue had higher concentration in pelvic fin, while solid Red had higher in pectoral and dorsal fins. Age, phenotype and their interaction influenced pigment deposition. Determinations of pigment levels, high temperature tolerant of pigments and in vitro digestibilities of pigments, protein and carbohydrate from twenty natural sources indicated that fermented red rice was the most suitable pigment source, following with Chlorococcum sp.     

Bacterial community structure and activity in fish farm sediments of the Ligurian sea (Western Mediterranean)

The environmental impact of a well-established fish farm has beeninvestigated in surface sediments of the Ligurian Sea in order to assess thebiodeposition, bacterial community structure and dynamics at a mature stage oforganic enrichment.The Biopolymeric carbon (BPC) fraction of organic matter and phytopigmentconcentrations displayed very high values beneath the fish cages. In particularlipid, carbohydrate and chlorophyll-a concentrations werehigher in farm sediment while protein concentrations did not show significantchange between farm sediment and control.Benthic bacteria were closely related to organic enrichment and their densitywas three times higher (up to 3 × 10¹⁰ cellsg^–1) in stations beneath the cages being positivelycorrelated with BPC (n = 10, p < 0.05) and lipid (n = 10, p < 0.05)concentrations. Colony forming units (CFU) counts of heterotrophic bacteriaindicate a shift in the relative importance of the gram negative bacterialfraction, displaying the predominance of theCytophaga/Flexibacter-like bacteria (CBF), as well as theoccurrence of pathogenic bacteria (such as Vibrio) insediments beneath the farm. In contrast, Gram positive bacteria were moreprevalent in control site where they represented up to 90% of total isolates.Aminopeptidase activity displayed higher values in sediment beneath the cages,whereas the enzymatic activity per bacterial cell was lower. These data suggesta functional stress of bacterial degradation rates and represent a potentialvaluable environmental index of imbalance between supply and removal of organicmatter in eutrophicated environments.Data presented in this study also suggest that either the biochemicalcomposition of sedimentary organic matter as well as the selected microbialvariables may represent useful tools for evaluating the effects of organicenrichment due to fish farming and could be proposed as new environmentalindices of aquaculture impact on marine sediment.     

Common bottlenose dolphin (Tursiops truncatus) interaction with fish farms in the Gulf of Ambracia,western Greece

1. Marine aquaculture, and its fast-growing development, has the potential for wider environmental, ecosystem, and biodiversity impacts. This study assesses the impact of fish farming on a bottlenose dolphin (Tursiops truncatus) population within the Gulf of Ambracia (western Greece) between 2007 and 2018. Two different study areas were defined in order to investigate differences on occurrence, abundance, behaviour, and seasonal fluctuations between them: a ‘control area’, in the north-western side of the Gulf; and a ‘fish farm area’, in the south west, where the highest density of fish farm cages is found.
2. A total of 169 daily surveys were dedicated to the control area and 74 days were dedicated to the fish farm area, yielding 104 and 37 sightings, respectively. Both the probability of detecting dolphins (U = 6,763.000, P = 0.002) and the group sizes (U = 578.000, P < 0.001) were smaller around fish farms.
3. Seasonality analyses were restricted to 2007–2008, as this was the period with year-round effort. Results revealed that dolphins were more frequently seen around fish farms in the winter (Kruskal–Wallis test, P = 0.036).
4. From the 40 identified individuals that were re-sighted at least 10 times during the study period, 21 used the fish farm area less than expected according to sampling effort, and 10 of them were never observed in that area (binomial test, P < 0.05).
5. The results revealed an impact of fish farms on the distribution of bottlenose dolphins in the Gulf of Ambracia. This information should be taken into consideration when defining ecosystem-based management measures within the management plan, which is currently in preparation for this Natura 2000 site.

     

Environmental effects of a marine fish farm of gilthead seabream (Sparus aurata) in the NW Mediterranean Sea on water column and sediment

This study examined the effects of organic enrichment on water column, sediments and macrofauna caused by a fish farm in the Mediterranean Sea. Samples were collected on four sampling campaigns over a one‐year cycle. Significant differences were found in the water column in dissolved oxygen, dissolved inorganic nitrogen, phosphate and total phosphorus concentrations between the fish farm and the control. The increase in the dissolved inorganic nitrogen and phosphate concentrations at the fish farm modified the stoichiometric ratios between nutrients, with silicate acting as limiting nutrient at the fish farm 11% more than at the control. Nevertheless, chlorophyll a concentration in the water column was higher at the control station, probably due to the fouling of the underwater fish farm structures. Significant differences were found in sediment concentrations of organic matter, total phosphorus and redox potential between the fish farm and the control. The Canonical Correlation Analysis indicated that organic matter, total phosphorus, redox potential and% of gravels accounted for 68.9% of the total variance in the species data. Changes were observed in macrofauna, with a decrease in number of species and up to a nine‐fold increase in abundance with respect to the control.     

Abundance of sulphate-reducing bacteria in fish farm sediments along the coast of Japan and South Korea

The abundance of sulphate-reducing bacteria (SRB) was investigated in the coastal marine sediments along the coast of Japan and South Korea. Sediment samples were collected from fish and shellfish farms between 2006 and 2008. As non-fish farming reference sites, sediments were also collected from highly eutrophic bays, a highly sulphidogenic saline lake, and the deep sea. A quantitative real-time PCR analysis that targeted the gene coding for a portion of the α-subunit of dissimilatory sulphite reductase (dsrA) was performed to assess the abundance of the SRB in the sediments. Between 2.8 × 10⁷ and 2.5 × 10⁹ copies of the dsrA gene per gram dry sediment were detected. There was no relationship between dsrA gene copy number and total bacterial count in the sediments, whereas organic matter contents (particulate organic carbon and nitrogen, ignition loss and chemical oxygen demand) and acid-volatile sulphide contents were significantly correlated with the dsrA copy number. The data presented demonstrate that organic enrichment of sediment may influence the abundance of SRB communities in coastal marine sediments and that the cell density of SRB may be used as a biological indicator for assessing pollution levels in sediments of marine fish farms.     

Benthic nutrient fluxes at longline sea squirt and oyster aquaculture farms and their role in coastal ecosystems

To assess the impact of aquaculture activities, we measured the primary production, total sediment oxygen consumption, and benthic nutrient flux at two aquaculture farms (sea squirt and oyster) and one reference site. The estimated primary production in the water column ranged from 19–169 mmol C m⁻² d⁻¹. Total sediment oxygen consumption rates ranged from 58 to 328 mmol m⁻² d⁻¹, 1.1 to 40 mmol m⁻² d⁻¹ for nitrogen, 0.17 to 3.0 mmol m⁻² d⁻¹ for phosphate, and 7.3 to 74 mmol m⁻² d⁻¹ for silicate. The average total sediment oxygen consumption at the longline farms was >2.5 times higher than the reference site. Nitrate was significantly removed by denitrification at the longline farms in July and September and ranged from −5.4 to −0.09 mmol m⁻² d⁻¹, which is higher than for other coastal sediments. The benthic fluxes of nitrogen and phosphate at longline farms were up to 16 and six times higher than at the reference site, respectively. The average nitrogen requirements of the primary producers were 9.3 mmol m⁻² d⁻¹ at the sea squirt farm, 7.0 mmol m⁻² d⁻¹ at the oyster farm, and 13.5 mmol m⁻² d⁻¹ at the reference site, corresponding to 88, 316, and 27.2% of the nitrogen supplied by benthic fluxes, respectively. Our results suggest that benthic nutrient fluxes at longline farms are a major nutrient source for primary production in coastal waters.     

Sedimentation of organic matter from fish farms in oligotrophic Mediterranean assessed through bulk and stable isotope (δ13C and δ15N) analyses

Bulk sedimentation and carbon and nitrogen stable isotopes were used to investigate the dispersion of particle waste products from 3 fish farms distributed along the Mediterranean Sea and characterized by the seagrass Posidonia oceanica growing in immediate vicinity of the fish cages. The farms were located at sites with rapid water exchange (average current speeds > 5.5 cm s^− 1) and water depths ranging from 16 to 28 m. Sedimentation traps were deployed along transects from each farm on bare and vegetated sites for 48 h during summer, where the production in the farms is at maximum. The sedimentation under the net cages was 8 to 25 times higher than at control sites located 1 km away. The farm with the largest production showed the highest sedimentation rates. Phosphorus (P) deposition rates were particularly high at all farms, and the underlying sediments were enriched in P. These results indicate that P can be used as a sensitive indicator of farm loadings. The isotopic signals (δ¹³C and δ¹⁵N) of the sediment trap materials at the control sites varied among the 3 study sites (δ¹³C − 14.9‰ to − 23.4‰ and δ¹⁵N 2.2‰ to 6.2‰), but some general trends were observed with less negative δ¹³C and more positive δ¹⁵N signals under the net cages. These signals were reflected in the underlying sediments, in particular for δ¹⁵N, suggesting that N isotopes can be used as indicators of farm waste products in traps and sediments.     

Evaluation of three phytoplankton species as food for the pearl oyster <Emphasis Type="Italic">Pinctada fucata</Emphasis>

In the pearl cultivation farms of the Ehime Prefecture, Japan, mass mortalities of the pearl oyster Pinctada fucata have occurred since 1994. The occurrences of mass mortality roughly coincided with a shift of the dominant phytoplankton from Skeletonema and Chaetoceros to Chaetoceros and Nitzschia all of which belong to Bacillariophyceae. Hence, we evaluated Nitzschia, together with Chaetoceros and Isocrysis, as food for the oyster. Wet weights, lengths, widths, glycogen contents, and growth rates in terms of wet weight of the oysters in all the feeding treatments were significantly higher than those in the non-feeding treatment. The highest glycogen content (2.34%) and growth rate (2.21 g month⁻¹) were found in the Chaetoceros treatment. Growth rate in the Isocrysis treatment (1.63 g month⁻¹) was also high, although glycogen content in this treatment (0.41%) was low. In the Nitzschia treatment, growth rate of the oyster (0.94 g month⁻¹) was the lowest and glycogen content (0.83%) was also low relative to that in the Chaetoceros treatment. Chlorophyll a concentration in fecal pellets was lowest in the Nitzschia treatment (<2.7 μg mg⁻¹), suggesting more complete digestion of Nitzschia by the oyster. Thus, Nitzschia was edible and digestible but not assimilated by P. fucata. We propose the following scenario for the relationship between Nitzschia dominance and mass mortality. When Nitzschia dominates in a culture area, the physiological condition of P. fucata deteriorates due to low assimilation of Nitzschia by the oyster, followed by susceptibility of the oyster to infection by agents lethal to the oyster.     

Growth variations within a farm of mussel (Mytilus galloprovincialis) held near fish cages: importance for the implementation of integrated aquaculture

Fish farming releases extensive amounts of particulate organic waste that can be exploited by bivalves in integrated culture. We tested if mussels Mytilus galloprovincialis cultured at two depths (1 and 6 m) in a raft, moored 170 m from a fish farm had greater growth than bivalves held 550 m from the fish cages. Mussel growth was monitored monthly, covering the second phase of the culture, from thinning‐out to harvest (March to November 2011). We also studied if fish solid and dissolved nutrients increased the organic content of the seston and chlorophyll‐a levels near the fish cages through weekly samples. Results showed no differences in seston, chlorophyll and physiochemical characteristics of the water among rafts. Maximum growth and Condition Index (CI) occurred during spring–summer (April–August), when mussels had access to greater food quality and quantity. Mussels cultivated close to the cages showed similar shell length, weight and CI compared with mussels distant from the fish farm. Average shell length, meat dry weight and CI at harvest were 76.31 mm, 2.51 g and 23%. Bivalves cultured distant from the fish cages displayed 26% higher biomass than the other raft at the end of the experiment. Differences in biomass were explained by the significantly higher recruitment of mussel seed observed at the raft distant from the fish cages from June to November. The lack of a significant enhancement in growth of the bivalves cultured next to finfish is discussed.     

Determination of minimal concentration of Piscirickettsia salmonis in water columns to establish a fallowing period in salmon farms

A highly sensitive real‐time PCR procedure to detect and quantify the number of Pisciricketsia salmonis units in seawater samples from affected farm sites has been developed. The purpose was to determine a fallowing period that would allow safe restocking of the target farm with new fish. Bacterial load was determined in water samples by comparing the obtained amplification values against a standard curve generated by the amplification of known concentrations of the ITS‐ribosomal component of P. salmonis DNA, cloned in a suitable vector. The standard curve was linear over the range of 10¹–10¹⁰ log units. Target samples were taken every 10 days over a 40‐day period, at 5 m depth and at the surface. In a highly affected area of southern Chile, the number of bacterial units in farm water decreased to zero at day 50. Therefore, a fallowing period of 50 days post‐removal of cages of affected fish appears to be appropriate before restocking. This procedure could be adapted to control disease problems because of other pathogens in fish farm waters.     

Effects of organic effluents from a salmon farm on a fjord system. I. Vertical export and dispersal processes

Vertical flux of organic waste from a Norwegian salmon farm (which produced 2910 tonnes of fish in 19 months) located in 230-m-deep water was measured nine times in the course of 2 years by sediment traps along a transect stretching from the farm and 3 km out towards the sea. The chemical composition of the trapped material and the sediment below the traps were analyzed. The results showed that when the fish farm was empty, sedimentation rates of organic matter were similar all along the transect. Throughout the production cycle high and very variable sedimentation rates of particulate organic matter, particulate organic carbon and particulate organic nitrogen were measured within 250 m from the farm, while between 550 and 3000 m away from the farm sedimentation rates were lower and constant throughout the cycle. During the second year of production, the annual vertical flux of particulate organic carbon to the bottom adjacent to the farm was 365 g m^− 2, nine times as high as what was found 3 km away from the farm. While the sedimentation rates showed that most of the waste matter settled within 250 m of the farm, the fatty acid composition and δ¹³C isotope ratio of the material in the bottom traps indicate that some components of the organic waste were transported as far as 550 to 900 m, probably due to resuspension of surface sediment. Despite the high sedimentation rates the content of sedimentary organic matter, total organic carbon and total organic nitrogen was not elevated in the sediment around the farm. However, phosphorus was found in higher concentrations in the sediments close to the farm, indicating that organic matter had settled on the sediment and been decomposed. The unchanged content of organic matter in the sediment during the production cycle showed that at this site the local resuspension and dispersal conditions and the decomposition capacity of the benthos were sufficient to prevent overloading of the locality.     

Siltation increases the susceptibility of surface‐cultured eastern oysters (Crassostrea virginica) to parasitism by the mudworm Polydora websteri

Mudworm (Polydora websteri) parasitism is known to result in unsightly mud blisters in eastern oysters (Crassostrea virginica), resulting in reduced product quality and increased vulnerability to illness and environmental stress. While typically a concern only for bottom‐grown oysters, an abnormal severe outbreak of P. websteri in surface‐cultured oysters in New Brunswick, Canada, was reported in 2013, along with an anecdotally reported concurrent increase in siltation. Although heavier loads of silt are reported to increase P. websteri infestations in oysters, studies report mixed effects of siltation to this regard. Here, we report the results of a field experiment testing the effect of siltation on P. websteri recruitment in surface‐grown oysters at an aquaculture site in Richibucto, New Brunswick. Live oysters of similar size were deployed at the aquaculture site and were left to collect P. websteri recruits under one of two siltation treatments (high vs. low) for 50 days. Results suggested that P. websteri recruitment correlated with metrics of oyster size (shell weight, length, width, depth and surface area). When P. websteri counts were standardized for oyster shell morphometry, P. websteri recruitment was significantly higher in oysters exposed to the high siltation treatment, accumulating approximately 1.5× as many P. websteri as oysters exposed to the low siltation treatment. Our results suggest that higher amounts of siltation on surface‐cultured oysters can result in increased rates of P. websteri parasitism. Enhanced cleaning regimes may help to alleviate the impacts of P. websteri in surface‐grown oysters, although other mitigation strategies exist.     

Ecological damage assessment and compensation for reclaimed coastal pond aquaculture: A case study in Qingduizi Bay,China

Mariculture ponds, most of which are reclaimed from coastal wetlands, have increased dramatically worldwide. However, ecological damage and compensation of these reclaimed mariculture ponds have not been assessed. A framework was presented to assess ecological damages of reclaimed pond mariculture and applied to the Qingduizi Bay, a typical pond mariculture area in the northern Yellow Sea of China. The results show that ecosystem services affected by reclaimed pond mariculture include marine capture fishery, gene resource provision, climate regulation, erosion control, waste treatment, science and education value, nutrient cycle and storage, and nursery/habitat. Among the values obtained from all services, the average score of damage severity to habitat services (0.74) was the highest. The total value of ecological damage associated with reclaimed mariculture in Qingduizi Bay was approximately 86,858.48 yuan hm^?2 a^?1, which is 29 times higher than the sea usage fee standard (3,000 yuan hm^?2 a^?1) currently implemented. Results suggest that the government should update the sea area usage fee with ecological damage compensation for reclamation mariculture and collect enough money to restore damaged marine ecosystem. Moreover, the general framework could also be transferable to other reclamation pond mariculture areas and used to examine reclamation mariculture proposals at different scales.     

Biodegradation potential of aquaculture chemotherapeutants in marine sediments

The commercial chemotherapeutant formulations SLICE^® and AlphaMax^® [active ingredients emamectin benzoate (EB) and deltamethrin respectively] are used in fin fish aquaculture to control parasitic sea lice. In some regions, the use of these substances has drawn concern from the commercial fishing industry regarding potential adverse effects on non‐target organisms. In the present work, biodegradation of EB and deltamethrin, and their commercial formulations, was investigated over 135 days at 4 and 10°C in fresh marine sediments collected from underneath an active open net‐pen salmon farm. EB incubated as either pure substance or commercial formulation was recalcitrant at both temperatures under abiotic and biotic conditions. Deltamethrin incubated alone or as its commercial formulation degraded slowly at 10°C (t_1/2 = 330 ± 107 and 201 ± 27.1 days respectively). At 4°C, deltamethrin degradation was only significant following incubation as commercial formulation (t_1/2 = 285 ±112 days). Degradation rates of EB and deltamethrin as pure substances versus their commercial formulations were not statistically different. Depletion of deltamethrin was observed in 10°C inactive sediments indicating that transformation occurred (at least in part) via an abiotic pathway. Overall, these data provide further insight into the fate and persistence of EB from the ongoing use of SLICE^® in British Columbia's salmon aquaculture industry. AlphaMax^® is not registered in Canada but is used in other salmon farming countries to control sea lice.