A simple approach for the estimation of food consumption from growth rates at different environmental conditions and its application to juvenile cod (Gadus morhua L.) of a fjordic sea loch on the west coast of Scotland

Abstract Growth and condition of fish are functions of available food and environmental conditions. This led to the idea of using fish as a “consumption sensor” for the measurement of food intake over a defined period of time. A bio-physical model for the estimation of food consumption was developed based on the von Bertalanffy model. Whereas some of the input variables of the model, the initial and final lengths and masses of a fish and the temperature within the time period considered can easily be measured, internal characteristics of the species have to be determined indirectly. Three internal parameters are used in the model: the maintenance consumption at 0°C, the temperature dependence of this consumption and the food efficiency, the percentage of the ingested food utilized. Estimates of the parameters for a given species can be determined by feeding experiments. Here, data from published feeding experiments on juvenile cod, Gadus morhua L., were used to validate the model. The average of the relative error for the food intake predicted by the model for individual fish was about 24 %, indicating that fish used the food with different efficiencies. However, grouping the fish according to size classes and temperature lowered the relative error of the predicted food intake for the group to typically 5 %. For a group containing all fish of the feeding experiment the relative prediction error was about 2 %. Zusammenfassung Wachstum und Kondition der Fische sind von der verfügbaren Nahrung und von Umweltbedingungen abhängig. Dies führte zur Idee, Fisch als „Konsum-Sensor“ für die Messung der Nahrungsaufnahme über einen definierten Zeitraum zu verwenden. Auf Grundlage des von Bertalanffy-Modells wurde ein bio-physikalisches Modell zur Schätzung der Futteraufnahme entwickelt. Während einige der Eingangsgrößen des Modells leicht gemessen werden können (Anfangs- und Endlänge und -körpermasse der Fische und die Temperatur innerhalb des betrachteten Zeitraum), können interne Parameter der betrachteten Art nur indirekt bestimmt werden. Drei interne Parameter werden in dem Modell verwendet: Die Erhaltungskonsumtion bei 0° C, die Temperaturabhängigkeit dieser Rate und der Wirkungsgrad der Nahrung (der Anteil der Nahrung ,der aufgenommen und verwendet und nicht ungenutzt wieder ausgeschieden wird). Die Modellparameter für eine bestimmte Art können durch Fütterungsversuche bestimmt werden. Um das Modell zu validieren wurden Daten aus veröffentlichten Fütterungsversuchen mit juvenilen Kabeljau (Gadus morhua L.) verwendet. Modell und Wirklichkeit weichen in der Regel voneinander ab. Der durchschnittliche relative Fehler der durch das Modell vorhergesagten Nahrungsaufnahme betrug für Einzelfische etwa 24%, was darauf hinweist, dass einzelne Fisch die Nahrung mit unterschiedlichen Wirkungsgraden verwerten. Allerdings senkte die Gruppierung der Fische nach Größenklassen und Temperatur den relativen Vorhersagefehler für die Nahrungsaufnahme der Gruppe auf etwa 5%. Für alle Fische im Fütterungsversuch ist der relative Vorhersagefehler etwa 2%.

The status of Arctic charr, Salvelinus alpinus (L.), in southern Scotland: a cause for concern

The objective of this article is to review the populations of Arctic charr in the south of Scotland which have become locally extinct, and the reasons for their demise. In the British Isles, the Arctic charr in individual lakes have been isolated from each other for thousands of years and have developed a variety of phenotypic characteristics which are probably genetically based. About 200 populations of Arctic charr have been recorded from different parts of the British Isles: approximately 12 in England, 50 in Ireland, 175 in Scotland and four in Wales. The threats to charr from acidification, afforestation, engineering schemes, angling and fish farming are assessed, and the establishment of new populations is proposed as a method of replacing extinct stocks or providing an additional safeguard for valuable stocks in threatened waters.

The relationship between smolt and postsmolt growth for Atlantic salmon (Salmo salar) in the Gulf of St. Lawrence

The interaction of ocean climate and growth conditions during the postsmolt phase is emerging as the primary hypothesis to explain patterns of adult recruitment for individual stocks and stock complexes of Atlantic salmon (Salmo salar). Friedland et al. (1993) first reported that contrast in sea surface temperature (SST) conditions during spring appeared to be related to recruitment of the European stock complex. This hypothesis was further supported by the relationship between cohort specific patterns of recruitment for two index stocks and regional scale SST (Friedland et al., 1998). One of the index stocks, the North Esk of Scotland, was shown to have a pattern of postsmolt growth that was positively correlated with survival, indicating that growth during the postsmolt year controls survival and recruitment (Friedland et al., 2000). A similar scenario is emerging for the North American stock complex where contrast in ocean conditions during spring in the postsmolt migration corridors was associated with the recruitment pattern of the stock complex (Friedland et al., 2003a, 2003b). The accumulation of additional data on the postsmolt growth response of both stock complexes will contribute to a better understanding of the recruitment process in Atlantic salmon.

Coarse fish in Scotland: a threat or a resource?

This brief article summarizes the ecological role of non-salmonid fishes in Scottish fresh waters. Most government-sponsored research has focused on the ecologically valuable salmonids in this area, yet non-salmonid species are widely distributed in Scotland and play an important ecological role in freshwater ecosystems. The fish fauna of Scotland differs from other parts of the British Isles by being more impoverished following the end of the last Ice Age, ca. 10 000 years ago.

Glossoma intermedium survey. Scotland, April 5th to April 10th 2012

The British Glossomatidae contains seven species, split between the genera Glossosoma, Agapetus and Synagapetus. One species, Glossosoma intermediumhas not been recorded in England since 2003. This was found in a side stream of Hayeswater gill in the Lake District. The main purpose of this survey was to try and locate and record Glossosoma intermedium and was a follow up to a similar survey we carried out in the Glennshee area of Scotland during April 2011. Additionally, as in the 2011 survey it also made sense that while looking for the larvae, pupae and adults of Glossosoma intermediumwe could also record other species of caddisfly (Trichoptera), mayfly (Ephemeroptera) and stonefly (Plecoptera).

Zustand und Entwicklung ausgewählter Fischbestände: Einschätzung des ICES im Herbst 2003

During the autumn session of the ICES Advisory Committee for Fisheries Management (ACFM) 58 stocks assessed in 7 Working Groups have been analyzed and reviewed, among these the demersal stocks in the North Sea and the Mackerel stock. As in previous years, ICES recommends a reduction in fishing mortality for a number of stocks or even the establishment of recovery and management plans, to safeguard a continuous development of the stocks towards safe biological limits. ICES reiterated last year’s recommendation to close the directed cod fishery and any fishery taking cod as by-catch in the North Sea, west of Scotland and in the Irish Sea. This year, the stocks of plaice in the North Sea, southern hake and southern anglers are (among others) in a critical state and in urgent need of protecting or rebuilding measures. This will again have an enormous impact on almost all mixed fisheries in the European Union.

Zustand und Entwicklung ausgewählter Fischbestände - Einschätzung des ICES im Herbst 2002

During the autumn session of the ICES Advisory Committee for Fisheries Management (ACFM) 58 stocks assessed in six Working Groups have been analysed and reviewed, among these the demersal stocks in the North Sea and the Mackerel stock in the North East Atlantic. As in previous years, ICES recommends a reduction in fishing mortality for a number of stocks or even the establishment of recovery and management plans, to safeguard a continuous development of the stocks towards safe biological limits. ICES recommended the closure of the directed cod fishery and any fishery taking cod as by-catch in the North Sea, west of Scotland and in the Irish Sea. This will have a significant impact on the mixed round fish fisheries targeting haddock and whiting.

Die Bedeutung biologischer Daten aus der deutschen Seelachsfischerei für Bestandsabschätzung und Management

Since 1999, the ICES Working Group on the Assessment of Demersal Stocks in the North Sea and Skagerrak assesses the saithe stock in the North Sea, Skagerrak and west of Scotland as a single stock unit. The sampling, evaluation and role of biological data from the German saithe fishery in the assessment are described. The German data showed similar trends as observed in French and Norwegian series. Based on these estimates, the spawning stock recovered to more than 200 000 t due to reductions in quotas and exploitation rates. Thus, the production of the stock increased also in combination with good recruitment and positive trends in spawning stock size and landings were projected for 2002. The biological data derived from the German saithe fishery dominated the assessment of stock size, structure and exploitation. This fact encourages a continuation of the described analyses based on sampling onboard fishing vessels and fish markets by the Institute for Sea Fisheries. The successful collaboration with the saithe fishing industry is judged as an important contribution to the sustainable management of fish stocks.

Fangquoten für die EU-Mitgliedsländer 1998

The fishery ministers of the EU agreed in their yearly pre-Christmas marathon session on 18th and 19th Dec. 1997 on next year’s TACs and country quota. Main decision was the increase of the TAC for North sea cod and a smaller than feared cut of cod TACs in the West of Scotland zone, the Irish Sea and the English Channel. For the first time ministers set country quota for horse mackerel; until 1997 there had been - with the exception for Portugal and Spain - only a common quota. Also for the much disputed sandeel fishery a TAC of 1 mio. t was finally established, as well as for bluefin tuna and swordfish in the Atlantic and Mediterranean. For 1998 the EU member countries dispose of a total catch quota of 4.46 mio. t in EU waters, and together with quota in third country waters of 5.2 mio. t. Of this total quota, 3.16 mio. t are fish for human consumption and 2.1 mio. t fish for industrial purposes.

Die Situation der Makrelen- und Stöckerbestände. Der deutsche Beitrag zur internationalen Bestandsabschätzung

The question has not yet been completely solved whether or not the mackerel and horse mackerel stocks in the waters from the Bay of Biscay to the Atlantic off the Norwegian coast are independent unit stocks or must be regarded rather as one stock with distinct stock components. The stock definition, however, is the basis for fishery management and is fundamental for the exploitation of the stocks. For this reason the extensive mackerel and horse mackerel egg survey carried out in 1998, is of high importance and significance for the fishery management of the two species. The survey has begun in January in Iberian waters and will eventually end in the autumn north of Scotland. To cope with this task research vessels of eight European nations are participating.

Nematodenlarven in Heringen aus verschiedenen Fanggebieten

The prevalence of nematodes in herring from five different fishing grounds of the North Sea and west of Scotland were examined. The abundance of nematode larvae in the flesh of the North Sea herring was approximately twice as high and the abundance in the body cavity was more than 6 fold of the herring from fishing grounds west of Scotland. The worm burden in the flesh was not correlated to the length of the fishes but the worm burden of the body cavity tends to increase by length. The frequency distribution of the nematodes in the flesh and the influence of the catching season is also discussed.

Faunistic studies

An update on the work undertaken by the authors, Macan and Hynes, over the past year. Macan provides details of additional work undertaken since his publication of faunistic work on adult animals, including details on additional field data, further developments of the conclusions intially drawn and further comparisons with fauna of the highlands of Scotland. Two histograms are provided showing succession of Corixidae in two separate waterbodies. Habitat conditions are also discussed for this species and a number of locations are mentioned including, Blelham Tarn, Derwentwater and Rusland Moss. An update on stonefly work undertaken by Hynes is provided, specifically stomach contents of nymphs and habitat preference. Details are also given of aquatic insects being breed by the staff for research.