Trophic dynamics in two South American estuaries encompassing industrial development and a biodiversity hotspot

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规模化猪场甲烷排放通量测量与分析

畜禽粪便是温室气体甲烷排放的一个重要来源,养殖场蓄粪池的甲烷排放量受排入粪便性质、外界温度、风速以及诸多因素影响。为了研究中国北方规模化猪场蓄粪池的甲烷排放潜力,本研究通过对北京市北郊一个代表性猪场甲烷排量的连续监测,得出春夏交替期间蓄粪池甲烷排放的变化规律。     

The long‐term changes in plankton composition: Is Bay Sivash transforming back into one of the world's largest habitats of Artemia sp. (Crustacea,Anostraca)?

Bay Sivash was a hypersaline lagoon but after construction of the North Crimean canal, it shifted to a brackish water state. In 2014, the canal was closed; a salinity increase started. In 2018 and 2019, plankton sampling was conducted in the bay at salinity from 30 to 100 g/L. A decrease in taxonomic diversity and total abundance was observed. Before November of 2018, Harpacticoida and chironomid larvae were the most common and abundant groups. Different stages of Artemia were consumed by invertebrate predators and fish at that time. In November 2018, Artemia stages contributed more than 90% to total zooplankton abundance at all sites excepting with salinity lower than 55 g/L. In June–July 2019, adult Artemia were at all sites with salinity higher than 82 g/L when there was no suppression by predators. A self‐sustaining Artemia population in the bay may recover in 2 or 3 years, when the average salinity would reach 80–90 g/L; total abundance of the active Artemia stages may reach 3000–5000 ind. M^?3 between April and August. The lagoon may become one of the world main habitats of Artemia having a significant impact to provide world's supply by its cysts.     

From land and sea,long‐term data reveal persistent humpback whale (Megaptera novaeangliae) breeding habitat in New Caledonia

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Co‐culture of sea cucumber Holothuria scabra and red seaweed Kappaphycus striatum

Commercially valuable sea cucumbers are potential co‐culture species in tropical lagoon environments, where they may be integrated into established aquaculture areas used for seaweed farming. In the current study, wild‐caught juvenile sea cucumbers, Holothuria scabra, and red seaweed Kappaphycus striatum were co‐cultured on Zanzibar, United Republic of Tanzania. Sea cucumbers (97 g ± 31 SD, n = 52) were cultured in mesh enclosures at initial cage stocking densities of 124 ± 21 SD and 218 ± 16 SD g m^?2 under seaweed culture lines. Over 83 days, individual growth rate (1.6 g d^?1 ± 0.2 SD) of sea cucumbers at low stocking density was significantly higher (χ² = 8.292, d.f. = 1, P = 0.004) than at high‐stocking density (0.9 g d^?1 ± 0.1 SD). Seaweed individual growth rates [6.27 (±0.3 SE) g d^?1] were highest in co‐culture with sea cucumber at low density but did not differ significantly from high sea cucumber density or seaweed monoculture treatments (χ² = 3.0885, d.f. = 2, P = 0.2135). Seaweed growth varied significantly (χ² = 35.6, d.f. = 2, P < 0.0001) with sampling period, with the final sampling period resulting in the highest growth rate. Growth performance for seaweed and sea cucumbers (χ² = 3.089, d.f. = 2, P = 0.21 and χ² = 0.08, d.f. = 1, P = 0.777 respectively), did not differ significantly between monoculture and co‐culture treatments, yet growth in co‐culture was comparable with that reported for existing commercial monoculture. Results indicate H. scabra is a highly viable candidate species for lagoon co‐culture with seaweed. Co‐culture offers a more efficient use of limited coastal space over monoculture and is recommended as a potential coastal livelihood option for lagoon farmers in tropical regions.     

Zero-water exchange shrimp farming systems (extensive) in the periphery of Chilka lagoon, Orissa, India

The extensive zero-water exchange shrimp farming system in the periphery of Chilka lagoon (Orissa, India) was studied. The study aimed to describe this unique farming system with special reference to dynamics of macrozoobenthos, production characteristics and economics. The study conducted was based on a general survey as well as monitoring of five individual farms over a complete production cycle. The farming practice in this area is characterized by complete absence of water exchange during rearing. Ponds in this area are generally shallow (mean 72 cm). Most of the water and soil quality characteristics of these farms are within acceptable levels. Macrozoobenthos belonging to 12 taxa were collected, amphipods (81%) and polychaetes (13%) being most numerous. Overall macrobenthic density of farms studied varied from 968 to 11,470 individuals/m² with a gross mean of 5644 individuals/m². There was no general pattern to the variation in abundance of various taxa in different phases of the rearing cycle, suggesting a low predatory pressure by shrimp in the farms studied. Shrimp production was highly variable (91–250 kg/ha), but generally low with a mean of 145 kg/ha. The net income of these farms was estimated to be Rs. 63,250 per crop per ha. Compared with shrimp farming system with regular water exchange in the same area, Chilka farms generated high benefit-cost ratio indicating high profitability and sustainability.     

Possible influence of reared gilthead sea bream (Sparus aurata, L.) on wild stocks in the area of the Messolonghi lagoon (Ionian Sea, Greece)

More than 25% of Greek fish farms and 20% of Greek hatcheries of gilthead sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) are located along the Western Hellenic coast. The part of sea bream production is about 60% of the total production of these species. During the last decade, a spectacular increase in both the number of farms and their production, accompanied by a substantial price decrease and modification of their structure and functioning, has been recorded. These changes resulted in the maintenance in cages of large individuals (more than 500 g) of gilthead sea bream which are potential spawners. The study, based on both the maturity stage and the decrease in individual mean weights during the reproductive period of the species, confirmed reproduction in cages. In parallel, during the last 5 years a remarkable increase (about 80%) in sea bream landings from the fish trap fisheries of the Messolonghi‐Etoliko lagoon, which is a typical nursery for the species, was recorded. The increase was accompanied by a decrease both in price and mean size of the 0‐group individuals. The possible influence of the rearing activities in the area, the density‐dependent mechanisms and the negative impacts of this unintentional enhancement of the traditional lagoon fisheries of the area are discussed.     

Annual and lunar-synchronized ovarian activity in two rabbitfish species in the Chuuk lagoon, Micronesia

ABSTRACT:   This study examined the annual and the lunar cycles of ovarian activity in the forktail rabbitfish Siganus argenteus (Quoy & Gaimard, 1825) and the spiny rabbitfish Siganus spinus (Linnaeus, 1758), which were collected from the Chuuk lagoon, Federated States of Micronesia. Gonadosomatic index (GSI) increased in May and June for S. argenteus . For S. spinus , GSI increased in March, and from July to September. During these periods, the ovaries of these species contained oocytes at the tertiary yolk stage or the maturation stage, suggesting that these months are the reproductive season of the two species. During the reproductive season, weekly collection of the fish according to the lunar phase revealed that high GSI occurred around the last quarter moon for S. argenteus and the new moon for S. spinus . In the ovaries, oocytes developed synchronously, and postovulatory follicles, an indicator of spawning, were observed after the respective moon phase, suggesting that these species are restricted lunar-synchronized spawners. Comparisons of the reproductive activity of the two rabbitfishes in the Chuuk lagoon with that in Okinawa waters revealed that there is a geographic difference in the reproductive activity between habitats. However, the lunar phase for exertion of synchronous gonadal maturation and spawning is common in both regions.