Search

Studied were the quantities of volatile amines, total volatile bases nitrogen (TVB-N) and trimethylamine nitrogen (TMA-N) in stored sardines ( Sardina pilchardus) and herring ( Clupea harengus) over a 24-h period after defrosting. At the beginning of the experiment analyses showed TVB-N quantities in the flesh of both species to be higher than the FAO-recommended limit. TMA-N concentrations exceeded the acceptance limit 6 h after defrosting in herring samples and after 12 h in sardines. During the entire experiment TMA-N and TVB-N concentrations in sardines were above the tolerance limit. The defrosting method usually applied in tuna farms is unsuitable for maintenance of a high quality food supply. Low quality baitfish can cause reduced weight gain as well as induce health problems and mortality in farmed tuna ( Thunnus thynnus) populations. [ABSTRACT FROM AUTHOR]

An application of a new automated fish counting device – the Riverwatcher System (RW) – was used to monitor upstream fish movements in a pool-and-weir fish pass in the River Zêzere, Portugal, for 141 days from June 2002 to May 2003. Fish populations were also collected downstream using multimesh gillnets (5 different mesh sizes ranging from 30 mm to 85 mm knot to knot; ratio between mesh sizes of about 1.30) and electrofishing for comparison with fish records produced by the RW. More than 3000 individual Iberian nase Chondrostoma polylepis ascended the fish pass and moved through the RW during the study period. However, only 18% of the records produced by the RW contained silhouettes similar to fish; no individual smaller than 15 cm TL was recorded by the counter. Most seasonal movements (73.9%) occurred in spring and were associated with reproduction. Displacements seemed to occur independently of time of day. Water temperature (range: 12–22°C) was the only significant environmental variable (P < 0.01) influencing upstream movements of this species. Further development of hardware and software will be necessary to improve performance of the counter, particularly in Mediterranean rivers, where more turbid waters and a greater proportion of small-size species are present. [ABSTRACT FROM AUTHOR]