Towards the identification of ecological management units: A multidisciplinary approach for the effective management of bottlenose dolphins in the southern Iberian Peninsula

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Survival and growth of geoduck clam larvae (Panopea generosa) in flow‐through culture tanks under laboratory conditions

The geoduck clam, Panopea generosa, is a species from the west coast of Baja California, Mexico, and the optimization of seed production systems is still a limiting factor for its aquaculture. In this study, a flow‐through culture system was designed and tested in P. generosa larvae. Survival and growth was compared in triplicate 45‐L fiberglass tanks using three larval densities (5, 10 and 15 larvae/ml). A head tank kept constant the water inflow, with a daily renewal rate of 1.8× tank volume. The food (Isochrysis spp.) was dosed according to the ingestion rate of larvae and the dilution rate. Survival decreased linearly during the first 10 days and reached asymptotic values of ca. 20% (15 larvae/ml) and 50% (densities of 5 and 10 larvae/ml) afterwards. Mean shell length at the end of the experiment (243 ± 1.8 to 270 ± 0.7 μm) was not statistically different among treatments, even though a trend towards higher gross growth rate was observed in the treatment with the lowest density (9.5 μm/day) relative to the rest of the treatments (8.5 μm/day). It is concluded that P. generosa larvae can be successfully grown in flow‐through systems at maximum densities of 10 larvae/ml without significantly affecting their survival and growth rates. The system design was reliable, kept a constant water flow with reduced maintenance, and may represent an important option in the laboratory for increasing the stocking density of Panopea species during the larval phase.     

Reproductive cycle of the south American scallop Amusium laurenti (Gmelin, 1791) (Bivalvia, Pectinidae)

Amusium laurenti is a functional hermaphroditewith well differentiated male and female gonadalareas. The gonadal index varies throughout the yearwith maximum values occurring in January, March andJuly, and minimum ones in August and September. Partial spawning (with respect to the individual andthe population) occurred from January to February andMarch to May. The major spawning event coincided withthe end of the period during which bottom watertemperature increased to temperatures above 26°C(July–August). Subsequently temperature decreased to22°C, with a period of gonadal restoration andincreasing gonadal index. Histological analysis ofthe gonads correlated with the gonadal index.     

Correction to: The development of the Norwegian wrasse fishery and the use of wrasses as cleaner fish in the salmon aquaculture industry

Fisheries Science - A correction to this paper has been published: https://doi.org/10.1007/s12562-021-01502-z     

Evidence of hybridization between Yaqui catfish Ictalurus pricei (Rutter, 1896) and channel catfish Ictalurus punctatus (Rafinesque, 1818) in north-west México revealed by analysis of mitochondrial and nuclear genes

1. The Yaqui catfish, Ictalurus pricei, is the only native ictalurid species described from north-west México and south-west USA. It is an endangered species owing to the decline and loss of most of its historical populations, mainly because of competition and hybridization with the non-native channel catfish, Ictalurus punctatus. The Arroyo Cajón Bonito is one of the few remnant populations of Yaqui catfish in the Yaqui River basin, and it is threatened by the presence of channel catfish that escaped from private culture facilities.
2. Phylogenetic analysis of two mitochondrial and two nuclear genes was used to detect evidence of hybridization with channel catfish in a collection of 20 catfish from Arroyo Cajón Bonito. Fourteen putatively pure Yaqui catfishes, five hybrids and one channel catfish were detected.
3. This study further highlights hybridization between channel and Yaqui catfish as the main threat to the remaining Yaqui catfish populations. We recommend urgent evaluation of the remnant populations of native catfish elsewhere and their current conservation status.

     

Stock enhancement programme for black sea bream, Acanthopagrus schlegelii (Bleeker), in Hiroshima Bay, Japan: a review

This paper reviews the stock enhancement programme for black sea bream ( Acanthopagrus schlegelii ) in Hiroshima Bay. This bay is one of the biggest production areas for black sea bream in Japan, accounting for about 10% of the total catch of the species in this country in 2004. After intensive fishing pressure caused a drastic decline in the catch of the species in this bay in the 1970s, a stock enhancement programme was conducted in its northern part since 1982 to restore the depleted population. The number of black sea bream juveniles released in 1996 surpassed 9 million, representing the third main species stocked in Japan. Almost 1.4 million of these juveniles were released into Hiroshima Bay. The fast acclimatization of hatchery-reared juveniles released into the bay may have contributed to the recovery of landings in the late 1980s and 1990s. However, this recovery was accompanied by a reduction in the market price of black sea bream. Further studies to assess the effectiveness of the stock enhancement programme as well as the carrying capacity of Hiroshima Bay to maintain the stock of black sea bream at a stable, healthy level are desirable. The necessity of evaluating the secondary effects derived from using a reduced number of breeders as well as finding new markets are suggested.     

Diversity analysis of <Emphasis Type="Italic">Acacia tortilis</Emphasis> (Forsk.) Hayne ssp. <Emphasis Type="Italic">raddiana</Emphasis> (Savi) Brenan (Mimosaceae) using phenotypic traits,chromosome counting and DNA content approaches

Acacia tortilis (Forsk.) Hayne ssp. raddiana (Savi) Brenan (Family Fabaceae; subfamily Mimosoideae) is a pioneer tree of dry areas. In spite of its several uses, there are no any published studies which deal with genetic diversity of Acacia tortilis (Forsk.) Hayne ssp. raddiana (Savi) Brenan in Tunisia. For this reason, here we study its genetic diversity with morphometric (only in Tunisian populations), chromosome counting, and cytometric (in Tunisian and Ziambabwean populations) approaches. Morphological field studies of four Tunisian populations (Bouhedma, Haddej, Hajeb and Gtar, respectively, designated as A, B, C, D) of A. tortilis (Forsk.) Hayne ssp. raddiana (Savi) Brenan using a general linear model (ANOVA) revealed statistically highly-significant differences between populations for all examined characters (P < 0.0001). Significant differences were found also between genotypes for the majority of morphological traits (P < 0.0001) except the width of 10 pods (laP), weight of 10 pods (Wt) and seed number of 10 pods (Sn) (P ≥ 0.110). The variability in the tree, pod and seed characters can be exploited for agro-industrial purposes. The DNA amount and chromosome numbers of populations Umguza and Gwaii River from Ziambabwe and of Tunisian populations A, B, C and D were determined. Tunisian populations had 2C nuclear DNA contents of 2.95–3.03 pg, and were shown to be tetraploid (2n = 4x = 52), whilst the two Ziambabwean populations had 1.39–1.40 pg and were diploid (2n = 2x = 26). It is suggested that the Tunisian populations are paleotetraploids, adapted to the more-arid local conditions.     

Monitoring glyphosate residues in transgenic glyphosate-resistant soybean

The availability of Roundup Ready (RR) varieties of soybean has increased the use of glyphosate for weed control in Argentina. Glyphosate [(N-phosphonomethyl)glycine] is employed for the eradication of previous crop vegetation and for weed control during the soybean growing cycle. Its action is effective, and low environmental impact has been reported so far. No residues have been observed in soil or water, either of glyphosate or its metabolite, AMPA (aminomethylphosphonic acid). The objective of this work was to monitor glyphosate and AMPA residues in soybean plants and grains in field crops in Santa Fe Province, Argentina. Five sites were monitored in 1997, 1998 and 1999. Individual soybean plants were sampled from emergence to harvest, dried and ground. Analysis consisted in residue extraction with organic solvents and buffers, agitation, centrifugation, clean-up and HPLC with UV detection. In soybean leaves and stems, glyphosate residues ranged from 1.9 to 4.4 mg kg(-1) and from 0.1 to 1.8 mg kg(-1) in grains. Higher concentrations were detected when glyphosate was sprayed several times during the crop cycle, and when treatments approached the flowering stage. AMPA residues were also detected in leaves and in grains, indicating metabolism of the herbicide.     

Fuzzy-logic-based feeder system for intensive tilapia production (<Emphasis Type="Italic">Oreochromis niloticus</Emphasis>)

In high-fish-density aquaculture systems, tilapia producers are compelled to provide 100% of food required to obtain profitable growth rates. It is well known that fish have a low food conversion rate and feeding represents the most important expenditure, approximately 40% of total production cost. Therefore, precise quantities of food should be provided to avoid water pollution and economic losses due to food waste when water conditions are inadequate for fish feeding. A way to control food provisions in this work was determined by the conditions of temperature, dissolved oxygen, fish age, and body weight, since these variables have a direct effect on fish metabolism and growth. Thus, a change in metabolism is reflected in a modification of energy requirements and, as a consequence, in variations of food consumption. In this work, a new feeder with fuzzy-logic control algorithms is proposed for fish feeding; this technique allows farmer knowledge to be taken into account in a series of if–then-type rules. To define these rules the temperature and dissolve oxygen were considered in order to provide precise food quantities. The results show minimal differences in growth (P > 0.05) between treatments, important food saving of 29.12% (equivalent to 105.3 kg), and lower water pollution (reduced water dissolved solids and ammonium components) compared with timed feeders. This system provides an important contribution to sustainability of intensive aquaculture systems, increasing productivity and profitability, and optimizing water use.