Mechanism of red colouration in Tovel-See (”Conclusions” only) [Translation from: Archiv fur Hydrobiologie 38 299-302, 1941]

Cases of red colouration in small lake basins, due to the abundant appearance of microorganisms have long been known. Usually it is caused by a fast, sudden, intensive propagation (so called ”bloom”) of Cyanophycae and bacteria. (e.g. Oscillatoracae, thiobacteria etc.). An exception to this is the red colouration of Tovel-See, an alpine lake basin in the Dolomites of the Brenta group (Trentino), lying at a height of 1178 m and hidden in the woodland of a valley. Here the red bloom has a double rhythm: a daily and a yearly rhythm. The colouration of one part of the lake takes place in the warmest months of the year (i.e. July, August, September) and in the middle hours of the day. The immediate origin of the bloom has been known for a long time: it is caused by the Peridinacae Glenodinium sanguineum. This paper describes the phenomenon of red colouration of the lake and discusses its conditions.

Estimation of the number of purse-seiner sets on tuna associated with dolphins in the Eastern Pacific Ocean during 1959-1980

ENGLISH: Annual estimates of the number of purse-seine sets made on tunas associated with dolphins are needed to estimate the total number of dolphins killed incidentally by the eastern Pacific tuna fishery. The most complete source of data, the Inter-American Tropical Tuna Commission's logbook data base, was used in this study. In the logbook data base, most sets are identified as being either associated with dolphins or not associated with dolphins. Some sets are not identified in this respect. However, the number of these unidentified sets which were associated with dolphins have been estimated by stratifying the logbook data according to whether or not any tuna were caught, whether or not the nearest identified set was associated with dolphins, and the distance to the nearest identified set. Most of the unidentified sets fell in strata characterized by a proportion of sets on tuna associated with dolphins that was lower than the overall unstratified proportion. Landings data were used to estimate the number of sets on tunas associated with dolphins from fishing trips not included in the logbook data base. SPANISH: Se necesitan las estimaciones anuales de la cantidad de lances realizados sobre atunes asociados con delfines para calcular todo el número de delfines muertos accidentalmente en la pesca atunera del Pacífico oriental. Se empleó en este estudio la fuente más completa-los datos de la Comisión Interamericana del Atún Tropical, proveniente de los cuadernos de bitácora. En éstos, la mayoría de los lances han sido identificados ya sea como asociados o no asociados con delfines. Algunos de los lances no han sido identificados a este respecto. Sin embargo, se ha estimado el número de estos lances asociados con delfines que no se habían identificado, al estratificar los datos de bitácora de acuerdo a si se había o no capturado atún, a si el lance identificado más próximo era o no un lance asociado con delfines y al averiguar la distancia del lance identificado más cercano. La mayoría de los lances sin identificar se colocan en los estratos caracterizados por una proporción de lances sobre atunes asociados con delfines, inferior a la proporción general sin estratificar. Se usaron los datos de los desembarques para calcular la cantidad de lances sobre atunes asociados con delfines en viajes pesqueros que no fueron incluídos en la base de los datos de bitácora. (PDF contains 73 pages.)

Investment prospects in integrated fish and poultry farming project: The Kainji Lake Research Institute integrated fish and poultry farm model

The paper examines the feasibility of a small-scale integrated fish and poultry farming project based on an existing experimental model currently in operation at the Kainji Lake Research Institute, New Bussa, Nigeria. Financial analysis reveals a viable investment based on the output from a 2 ha fish pond or reservoir

Design of a Recreational Fishing Survey and Mark-Recapture Study for the Blue Crab, Callinectes sapidus, in Chesapeake Bay

The development of bay wide estimates of recreational harvest has been identified as a high priority by the Chesapeake Bay Scientific Advisory Committee (CBSAC) and by the Chesapeake Bay Program as reflected in the Chesapeake Bay Blue Crab Fishery Management Plan (Chesapeake Bay Program 1996). In addition, the BiState Blue Crab Commission (BBCAC), formed in 1996 by mandate from the legislatures of Maryland and Virginia to advise on crab management, has also recognized the importance of estimating the levels and trends in catches in the recreational fishery. Recently, the BBCAC has adopted limit and target biological reference points. These analyses have been predicated on assumptions regarding the relative magnitude of the recreational and commercial catch. The reference points depend on determination of the total number of crabs removed from the population. In essence, the number removed by the various fishery sectors, represents a minimum estimate of the population size. If a major fishery sector is not represented, the total population will be accordingly underestimated. If the relative contribution of the unrepresented sector is constant over time and harvests the same components of the population as the other sectors, it may be argued that the population estimate derived from the other sectors is biased but still adequately represents trends in population size over time. If either of the two constraints mentioned above is not met, the validity of relative trends over time is suspect. With the recent increases in the human population in the Chesapeake Bay watershed, there is reason to be concerned that the recreational catch may not have been a constant proportion of the total harvest over time. It is important to assess the catch characteristics and the magnitude of the recreational fishery to evaluate this potential bias. (PDF contains 70 pages)

The role of sites of special scientific interest (SSSIs) in the conservation of British rivers

This paper discusses the particular contribution of the SSSI (Sites of Special Scientific Interest) as a way of nature conservation for rivers. In 1989, the Nature Conservancy Council proposed a dual selection system for selection of rivers; either (1) "Whole river" SSSIs representing the main types of river, or rivers which show classic and representative transitions down their lengths, or (2) "Sectional" SSSIs which are shorter stretches of river with high nature conservation interest. The NCC has recently classified all SSSIs with a river interest into 4 categories: - river SSSIs, river valley SSSIs, river adds interest - where the river clearly adds biological interest to the site, and rivers of incidental interest. The overall length of river SSSIs amounts to almost 1000 km.

Use of stereo camera systems for assessment of rockfish abundance in untrawlable areas and for recording pollock behavior during midwater trawls

We describe the application of two types of stereo camera systems in fisheries research, including the design, calibration, analysis techniques, and precision of the data obtained with these systems. The first is a stereo video system deployed by using a quick-responding winch with a live feed to provide species- and size- composition data adequate to produce acoustically based biomass estimates of rockfish. This system was tested on the eastern Bering Sea slope where rockfish were measured. Rockfish sizes were similar to those sampled with a bottom trawl and the relative error in multiple measurements of the same rockfish in multiple still-frame images was small. Measurement errors of up to 5.5% were found on a calibration target of known size. The second system consisted of a pair of still-image digital cameras mounted inside a midwater trawl. Processing of the stereo images allowed fish length, fish orientation in relation to the camera platform, and relative distance of the fish to the trawl netting to be determined. The video system was useful for surveying fish in Alaska, but it could also be used broadly in other situations where it is difficult to obtain species-composition or size-composition information. Likewise, the still-image system could be used for fisheries research to obtain data on size, position, and orientation of fish.

Prediction of discard mortality for Alaskan crabs after exposure to freezing temperatures, based on a reflex impairment index

Millions of crabs are sorted and discarded in freezing conditions each year in Alaskan fisheries for Tanner crab (Chionoecetes bairdi) and snow crab (C. opilio). However, cold exposures vary widely over the fishing season and among different vessels, and mortalities are difficult to estimate. A shipboard experiment was conducted to determine whether simple behavioral observations can be used to evaluate crab condition after low-temperature exposures. Crabs were systematically subjected to cold in seven different exposure treatments. They were then tested for righting behavior and six different ref lex actions and held to monitor mortality. Crabs lost limbs, showed ref lex impairment, and died in direct proportion to increases in cold exposure. Righting behavior was a poor predictor of mortality, whereas reflex impairment (scored as the sum of reflex actions that were lost) was an excellent predictor. This composite index could be measured quickly and easily in hand, and logistic regression revealed that the relationship between reflex impairment and mortality correctly predicted 80.0% of the mortality and survival for C. bairdi, and 79.4% for C. opilio. These relationships provide substantial improvements over earlier approaches to mortality estimation and were independent of crab size and exposure temperature.

A study of tagging methods for the sea cucumber Cucumaria frondosa in the waters off Maine

The sea cucumber fishery in waters off Maine is developing and has recently experienced great increases in landings, corresponding to expanding export markets. Between 1994 and 1996, reported landings ranged from one to three million pounds (Fig. 1). In 1999, reported landings were over eight million pounds and rose to over nine million in 2000 (Feindel1). Like other developing fisheries, we have little information about the biology and ecology of the sea cucumber off Maine, limited data on the fishery, and little knowledge about the key life history processes that characterize its population dynamics. Therefore, we have a limited understanding of the current status of the resource and the impacts the fishery may have on the stock.

Checklist of the shore fishes of the Mentawai Islands, Nias Island and the Padang Region of West Sumatra

This paper presents a checklist of reef fishes of West Sumatra and adjacent provinces. The list includes 362 species of 143 genera and 46 families and contains seven new records and nine probable new species for Indonesia. It also uses information from sources only available in Bahasa Indonesia. The relative paucity of the fish fauna in West Sumatra seems to be related to the habitat destruction caused by illegal fishing with explosives or poisons such as cyanide.