Sustainable shellfish aquaculture in Saldanha Bay,South Africa

The carrying capacity for bivalve shellfish culture in Saldanha Bay, South Africa, was analysed through the application of the well-tested EcoWin ecological model, in order to simulate key ecosystem variables. The model was set up using: (i) oceanographic and water-quality data collected from Saldanha Bay, and (ii) culture-practice information provided by local shellfish farmers. EcoWin successfully reproduced key ecological processes, simulating an annual mean phytoplankton biomass of 7.5 µg Chl a l^–1 and an annual harvested shellfish biomass of about 3 000 tonnes (t) y^–1, in good agreement with reported yield. The maximum annual carrying capacity of Small Bay was estimated as 20 000 t live weight (LW) of oysters Crassostrea gigas, or alternatively 5 100 t LW of mussels Mytilus galloprovincialis, and for Big Bay as 100 000 t LW of oysters. Two production scenarios were investigated for Small Bay: a production of 4 000 t LW y^–1 of mussels, and the most profitable scenario for oysters of 19 700 t LW y^–1. The main conclusions of this work are: (i) in 2015–2016, both Small Bay and Big Bay were below their maximum production capacity; (ii) the current production of shellfish potentially removes 85% of the human nitrogen inputs; (iii) a maximum-production scenario in both Big Bay and Small Bay would result in phytoplankton depletion in the farmed area; (iv) increasing the production intensity in Big Bay would probably impact the existing cultures in Small Bay; and (v) the production in Small Bay could be increased, resulting in higher income for farmers.     

Lead, cadmium, copper, nickel and iron in limpets, mussels and snails from the coast of ras Beirut, Lebanon

Samples of Patella coerulea (Linnaeus), Brachydontes variabilis (Krauss), Monodonta turbinata (Born) and surface seawater were collected at eight locations along the coast of Ras Beirut, Lebanon, and analysed for lead, cadmium, copper, nickel and iron. With the exception of cadmium, the metal levels found in the three molluscs appear to be high in relation to levels reported by investigators from other coastal areas. The average values for lead, cadmium and nickel within these animals were quite similar. Concentrations of copper in P. coerulea were lower, but concentrations of iron were much higher than those found in both B. variabilis and M. turbinata. Further studies of metal levels in various other intertidal organisms from Ras Beirut, together with investigations into the possible effects of seasonal changes on metal concentration and distribution, are currently under way.     

Lead and mercury concentrations in the coastal waters of North and South Lebanon

Seawater samples were collected from the coastal waters 200 m from the shore of North Lebanon and South Lebanon. The 128 samples were then analysed for the presence of lead and mercury by atomic absorption spectrophotometry. The lead concentrations in the north ranged from 0.11–0.66 ppm (average: 0.29 ppm) and those for mercury ranged from 1.84–12.88 ppm (average: 5.44 ppm). In the south, the range of lead concentrations was from 0.23–0.95 ppm (average: 0.71 ppm) and the range of mercury from 4.13–10.34 ppm (average: 7.31 ppm). Levels of concentrations can be directly related to density of population, industrial activity, continental runoffs and seasonal and weather changes.     

Plastic pellets on the coast of Lebanon

The occurrence of plastic pellets along the coast of Lebanon is being reported for the first time. Although a variety of colours, shapes, and sizes was observed, most pellets seemed to be either an opaque-white or transparentamber colour, cylindrical to oval or round, and 2–5 mm in diameter. A random sampling was taken and the results of thermal analysis showed the pellets to be of either high density polyethylene (opaque-white pellets), polymethyl methacrylate (transparent), or polystyrene (amber).The presence of these pellets is most likely due to waste disposal by the numerous plastics ‘factories’ in the country, or possibly, cargo-loss during sea transport of raw plastics materials.     

Plastic pellets on Spain''s ‘Costa del Sol’ beaches

Plastic pellets, ranging in diameter from 2.7 to 4.5 mm, were collected from thirteen beaches on the Costa del Sol of Spain (Algeciras to Almeria). Although the pellets were common on most beaches surveyed, they were abundant on only four. Eighty-seven per cent of those collected were made of low density polyethylene (opaque, cream-yellow, and amber pellets), 8% were of high density polyethylene (solid white button-like pellets and orange-red conical pieces), and 4% were of ethylvinyl acetate (clear to translucent pellets). The absence of ‘crazing’ and encrusting biota on the pellets suggests their recent introduction to this marine environment.     

Arsenic, cadmium, lead and mercury in canned sardines commercially available in eastern Kentucky, USA

Seventeen samples of canned sardines, originating from six countries and sold in eastern Kentucky, USA, were analyzed in composites of 3-4 fish each for total arsenic (As), cadmium (Cd) and lead (Pb) by graphite furnace atomic absorption spectrophotometry (AAS) and for mercury (Hg) by thermal decomposition amalgamation and AAS. Results in μg/g wet: As 0.49-1.87 (mean: 1.06), Cd < 0.01-0.07 (0.03), Pb < 0.06-0.27 (0.11), Hg ND < 0.09. Values fall generally within readings reported by others, but no internationally agreed upon guidelines have yet been set for As or Cd in canned or fresh fish. The incidence of cancers and cardiovascular diseases associated with As ingestion is extraordinarily high here. With the role of food-borne As in human illness presently under scrutiny and its maximum allowable limits in fish being reviewed, more studies of this nature are recommended, especially considering the potential importance of small pelagic fishes as future seafood of choice.