Kabeljaukrise in der Nordsee erfordert neue bestandserhaltende Maßnahmen

The European Commission has claimed a fundamental revision of the European Common Fisheries Policy in its Green Paper (EC 2001) by highlighting the reasons of continued overfishing of a number of valuable demersal fish stocks. Quotas in excess of scientific recommendations, fleet over capacities and poor enforcement of management decisions were identified causal for major stock and yield reductions while gaps in scientific advices were also criticized. The depleted cod stock in the North Sea, Skagerrak and Eastern Channel is the most prominent example. Existing and proposed management regulations were analysed by an expert group which met with fishing industry consultations in Brussels during 28 April – 7 May 2003. Depending on compliance with new technical regulations since 2000, the cod stock and its exploitation was found only marginally effected, while whiting displayed immediately significant losses in yield over long term and short term losses in haddock yields were reversed in substantial gains, also in SSB. However, reduction in fishing effort was found more effective in recovery potential than technical changes including closed areas, for which detailed information about variation in distribution of the stocks and the fisheries are required. Such effort reductions would reduce not only landings but also unregulated discarding, which is believed to be a major reason of the failure of the management measures in mixed fisheries. Recent trends in fishing effort of European fleets could not be quantified due to persistent data deficiencies.

Growth of yellowfin tuna, Thunnus albacares, in the Eastern Pacific Ocean based on otolith increments

ENGLISH: The growth of yellowfin tuna in the eastern Pacific is described in terms of several measurements taken from the fish and their otoliths (sagittae). Equations are also developed to predict age from the readily available dimensions of fork length and head length. The data for all of these relationships were obtained from a sample of 196 fish collected during 1977 through 1979 from purse seiners fishing north of the equator and east of 137°W. The fork-length range of the sample was 30-170 cm. The number of increments on a sagitta of each fish was used as a direct estimate of its age in days. The correspondence between increments and days has been validated for yellowfin in the length range of 40-110 cm. Circumstantial evidence indicates that the relationship also applies in the intervals of 0-40 cm and 110-170 cm. This circumstancial evidence was derived from: 1) literature on validated increments during early growth for other species, 2) knowledge that structures assumed to be daily increments on yellowfin otoliths have subsequently been validated in the corresponding zone on bluefin otoliths, and 3) a comparison of the growth curve based on increments to others obtained from length frequency modal analysis. Based on this information the age estimates over the entire size range of sampled fish are believed to be accurate. In addition to the general growth and age-predictive relationships, the major conclusions of the study are that: 1) Sexually dimorphic growth exists in terms of fork length, fish weight and the length of the otolith counting path for the entire data set. Examination of the data for 1977 and 1979 also revealed that the fork-length growth of each sex differed within years. 2) For combined sexes there were significant differences among the fork-length growth curves for yellowfin sampled in different years. 3) Yellowfin caught inshore (within 275 miles of the coast) were heavier than those caught offshore for fork lengths between 30 and 110 cm. The situation was reversed for lengths greater than 110 cm. 4) Back-calculated spawning months were distributed uniformly throughout the year in 1974 and 1977, but in 1975-1976 and 1978 spawning activity was apparently concentrated in the latter half of the year. SPANISH: El crecimiento del atún aleta amarilla en el Pacífico oriental se describe en términos de varias medidas obtenidas de peces y otolitos (sagita). Se formularon también ecuaciones para pronosticar la edad, según las dimensiones fácilmente disponibles de la longitud horquilla y longitud de la cabeza. Los datos de todas estas relaciones fueron obtenidos mediante una muestra de 196 peces recolectados desde 1977hasta 1979, en barcos cerqueros que estaban pescando al norte de la línea ecuatorial y al este de los 137°W. El intervalo de la longitud horquilla de la muestra fue de 30-170 cm. Se empleó el número de incrementos en la sagita de cada pez como un estimado directo de la edad en días. Se ha comprobado la relación entre los incrementos y los días en el intervalo de longitud de 40-110 cm del aleta amarilla. La evidencia circunstancial indica que se aplica también la relación a los intervalos de 0-40 cm y 110-170 cm. Esta evidencia circunstancial se dedujo: 1) de las publicaciones sobre incrementos comprobados de otras especies durante el primer crecimiento, 2) del conocimientoque las estructuras que se supone son incrementos diarios en los otolitos del aleta amarilla han sido comprobadas luego en la parte correspondiente de otolitos del aleta azul y 3) por una comparación de la curva de crecimiento, basada en incrementos relacionados a otras curvas obtenidas según el análisis modal frecuencia-talla. Se cree, basados en esta información, que las estimaciones de la edad sobre toda la amplitud de talla de los peces muestreados, es acertada. Además de la relación del crecimiento general y del pronóstico de la edad, las principales conclusiones de este estudio son: 1) En toda la serie de datos existe el crecimiento sexualmente dimórfico en términos de longitud horquilla, peso del pez y longitud del plano de conteo del otolito. El examen de los datos de 1977 y 1979, revelan también que el crecimiento longitud horquilla de cada sexo es diferente en los años. 2) En los sexos combinados hubo diferencias significativas entre las curvas de crecimiento longitud horquilla del aleta amarilla muestreado en diferentes años. 3) El aleta amarilla capturado cerca a la costa (en las primeras 275 millas) fue más pesado que el capturado en las aguas mar afuera, correspondiente a la longitud horquilla entre 30 y 110 cm. La situación fue inversa para tallas de más de 110 cm. 4) En 1974 y 1977, los meses retrocalculados del desove se distribuyeron uniformemente durante el año, pero en 1975-1976 y 1978, la actividad del desove se concentró aparentemente en el último semestre del año. (PDF contains 62 pages.)

Age, Growth, Life History, and Fisheries of the Sand Sole, Psettichthys melanostictus

Sand sole, Psettichthys melanostictus, is a small but important part of the west coast groundfish fishery. It has never been assessed and there is a limited amount of biological data for the species. We provide the first estimates of age and growth for California populations and compare them with studies from other areas. We found that sand sole is a rapidly growing species which may show a strong latitudinal gradient in growth rate. We also found evidence of a recent, strong cohortrelated shift in the sex ratio of the population towards fewer females. In addition we examined data from the Washington, Oregon, and California commercial fishery to make an initial determination of population status. We found that catch per unit of effort in commercial trawls experienced a decline over time but has rebounded in recent years, except central California (the southern part of its commercial range), where the decline has not reversed.

Spatial and Temporal Distribution of Sea Turtles in the Western North Atlantic and the U.S. Gulf of Mexico from Marine Recreational Fishery Statistics Survey (MRFSS)

Systematic surveys, along with opportunistic sightings, have provided important information on sea turtle (Cheloniidae and Dermochelydae) distributions, knowledge which can help reduce the risk of harmful human interaction. In 1991 and 1992, the Marine Recreational Fishery Sta- tistics Survey (MRFSS) of the National Ma- rine Fisheries Service, NOAA, provided a unique opportunity to gain additional, synoptic information on the spatial and temporal distribution of sea turtles along the U.S. Atlantic and Gulf of Mexico coasts by asking recreational anglers if they had observed a sea turtle on their fishing trip. During the spring and summer months of those years, as water temperatures warmed, the MRFSS documented an increase in sea turtle sightings in inshore waters and in a northward direction along the U.S. Atlantic Coast and in a westward direction along the northern Gulf of Mexico. This pattern reversed in the late summer and fall months as water temperatures cooled, with sea turtles concentrating along Georgia and both coasts of Florida. Although the MRFSS did not provide species or size composition of sea turtles sighted, and effort varied depending upon location of fishing activity and time of year anglers were queried, it did provide an additional and useful means of ascertaining spatial and temporal distributions of sea turtles along these coasts.

Wave forecasts associated with hurricane landfalls in the vicinity of Cape Lookout, North Carolina

Hurricanes can cause extensive damage to the coastline and coastal communities due to wind-generated waves and storm surge. While extensive modeling efforts have been conducted regarding storm surge, there is far less information about the effects of waves on these communities and ecosystems as storms make landfall. This report describes a preliminary use of NCCOS’ WEMo (Wave Exposure Model; Fonseca and Malhotra 2010) to compute the wind wave exposure within an area of approximately 25 miles radius from Beaufort, North Carolina for estuarine waters encompassing Bogue Sound, Back Sound and Core Sound during three hurricane landfall scenarios. The wind wave heights and energy of a site was a computation based on wind speed, direction, fetch and local bathymetry. We used our local area (Beaufort, North Carolina) as a test bed for this product because it is frequently impacted by hurricanes and we had confidence in the bathymetry data. Our test bed conditions were based on two recent Hurricanes that strongly affected this area. First, we used hurricane Isabel which made landfall near Beaufort in September 2003. Two hurricane simulations were run first by passing hurricane Isabel along its actual path (east of Beaufort) and second by passing the same storm to the west of Beaufort to show the potential effect of the reversed wind field. We then simulated impacts by a hurricane (Ophelia) with a different landfall track, which occurred in September of 2005. The simulations produced a geographic description of wave heights revealing the changing wind and wave exposure of the region as a consequence of landfall location and storm intensity. This highly conservative simulation (water levels were that of low tide) revealed that many inhabited and developed shorelines would receive wind waves for prolonged periods of time at heights far above that found during even the top few percent of non-hurricane events. The simulations also provided a sense for how rapidly conditions could transition from moderate to highly threatening; wave heights were shown to far exceed normal conditions often long before the main body of the storm arrived and importantly, at many locations that could impede and endanger late-fleeing vessels seeking safe harbor. When joined with other factors, such as storm surge and event duration, we anticipate that the WEMo forecasting tool will have significant use by local emergency agencies and the public to anticipate the relative exposure of their property arising as a function of storm location and may also be used by resource managers to examine the effects of storms in a quantitative fashion on local living marine resources.

Reproductive biology of male franciscanas (Pontoporia blainvillei) (Mammalia: Cetacea) from Rio Grande do Sul, southern Brazil

The reproductive biology of male franciscanas (Pontoporia blainvillei), based on 121 individuals collected in Rio Grande do Sul State, southern Brazil, was studied. Estimates on age, length, and weight at attainment of sexual maturity are presented. Data on the reproductive seasonality and on the relationship between some testicular characteristics and age, size, and maturity status are provided. Sexual maturity was assessed by histological examination of the testes. Seasonality was determined by changes in relative and total testis weight, and in seminiferous tubule diameters. Testis weight, testicular index of maturity, and seminiferous tubule diameters were reliable indicators of sexual maturity, whereas testis length, age, length, and weight of the dolphin were not. Sexual maturity was estimated to be attained at 3.6 years (CI 95% =2.7–4.5) with the DeMaster method and 3.0 years with the logistic equation. Length and weight at attainment of sexual maturity were 128.2 cm (CI 95%=125.3–131.1 cm) and 26.4 kg (CI 95% =24.7–28.1 kg), respectively. It could not be verified that there was any seasonal change in the testis weight and in the seminiferous tubule diameters in mature males. It is suggested that at least some mature males may remain reproductively active throughout the year. The extremely low relative testis weight indicates that sperm competition does not occur in the species. On the other hand, the absence of secondary sexual characteristics, the reversed sexual size dimorphism, and the small number of scars from intrassexual combats in males reinforce the hypothesis that male combats for female reproductive access may be rare for franciscana. It is hypothesized that P. blainvillei form temporary pairs (one male copulating with only one female) during the reproductive period.

Bycatch of billfishes by the European tuna purse-seine fishery in the Atlantic Ocean

Billfishes are a component of offshore ecosystems; thus it is important to quantify the impact of the tuna fishery on these species in the world’s ocean. The aim of this study was to assess the bycatch of billfishes generated by the tropical tuna purse-seine fishery in the eastern Atlantic Ocean. Information on bycatch was collected by observers at sea during the European Union Bigeye Program. With a total of 62 observers’ trips, conducted on Spanish and French vessels between June 1997 and May 1999, this project is the biggest observer program ever carried out in the European tuna purse-seine fishery. This study showed that billfish bycatch by the purse seiners is very low (less than 0.021% of the total tuna catches and less than 10% of the total billfish catches currently reported). A Monte Carlo simulation was performed to account for some uncertainties in the fishing strategies of purse seiners operating in this ocean. One of the findings of this study indicated that the temporary moratorium on fishing with FADs (fish aggregating devices), adopted by the European purse-seine fishery in the eastern Atlantic Ocean, produced a decrease in incidental catches of marlins from 600–700 metric tons (t) to less than 300 t. In contrast, this trend was reversed for sailfishes, for which the bycatch increased from 25 t to 45 t. The difficulty of defining indices that express the conservation status in marine fishes and that gauge key ecosystem parameters and the need to promote an ecosystem approach for large-pelagic-resource management which takes into account biologic and socioeconomic criteria are briefly discussed.

Alternative phosphorus sources for formulated fish feed

An experiment was conducted to evaluate the possibility of using inorganic fertilizer triple super phosphate (TSP), inorganic fertilizer 16:20 (a 16:20 grade fertilizer contains 16 percent N and 20 percent P20 5), rice-bran and duck-manure as phosphorus sources in formulated fish feed for Nile tilapia ( Oreochromis niloticus). Experiment was conducted for a period of 2 months in net-cages suspended in fertilized earthen ponds and all male sex-reversed Nile tilapia (9.39- 10.37 g) were used in the experiment. Seven treatments including one non-feed treatment were used in this experiment. Treatment 1 (non-feed), treatment 2 (-P) where fish fed with phosphorus non-supplemented diet acted as control 1 and treatment 3, 4, 5, 6 and 7 where fish fed with 3% di-calcium phosphate (DCP), 3% triple supper phosphate (TSP), 7% 16:20 inorganic fertilizer, 30% rice-bran and 30% duck-manure supplemented diet, respectively. Results showed that the TSP and 16:20 grade inorganic fertilizer supplementation in diets as phosphorus sources were equivalent to DCP (Di-calcium phosphate) supplementation in terms of growth performance, feed utilization efficiency and final body composition of Nile tilapia. Ricebran and duck-manure were not found as good phosphorus sources.

Purification and properties of Aspartate aminotransferase (E.C. 2.6.1.1) from skeletal muscle of Cirrhina mrigala

Aspartate aminotransferase (E.C. 2.6.1.1.) from the skeletal muscle of fresh water fish Cirrhina mrigala has been purified 40 fold by ammonium sulphate fractionation, adsorption on alumina Csub(8) gel and chromatography using DEAE-cellulose column and the properties of the purified enzyme studied. The pH optimum of the enzyme is 7.8. The Km value of aspartic acid and 2-oxoglutaric acid are found to be 2.8 x 10sub(-3) M and 1.0 x 10sub(-4) M respectively. The activity of enzyme is inhibited by p-chloromercurybenzoate, hydroxylamine hydrochloride and sodium cyanide. The inhibition by pchloromercurybenzoate is reversed by reduced glutathione, B-mercaptoethanol and cysteine. Dicarboxylic acids such as maleic acid, malic acid and succinic acid inhibit the enzyme activity. The enzyme is not activated by any of the metal ions tested and heavy metal ions such as mercury and silver strongly inhibit the enzyme activity.

Optimization of dose of methyltestosterone (MT) hormone for sex reversal in tilapia (Oreochromis niloticus L.)

This paper describes the optimization of dose of methyltestosteronei (MT) hormone for masculinization of tilapia (Oreochromis niloticus). Five treatments (i.e. T1 T2, T2, T4 and T5) with different doses such as 0, 40, 50, 60 and 65 mg of MT hormone were mixed with per kg of feed for each treatment and fed the fry four times a day up to satiation for a period of 30 days. The stocking density was maintained 10 spawn/liter of water. The growth of fry at different treatments was recorded weekly and mortality was recorded daily. At the end of hormone feeding the fry were reared in hapas fixed in ponds for another 70 days and at the 100th day the fish were sexed by the gonad squashing and aceto-carmine staining method. The analysis of growth data did not show any significant variation in length and weight of fish among the different treatments. High mortality of fry ranging 66% to 81.6% was observed in different treatments and highest mortality was observed during the first twelve days of the experiment. The sex ratio analysis showed that T2 (40 mg/kg) and T5 (65 mg/kg) produced 93.33% of sex reversed male and T3 (50 mg/kg) and T4 (60 mg/kg) produced 96.66% sex reversed male, and these ratios were significantly (p<0.05) different from 1:1 male: female sex ratio. The control, T1 (0 mg/kg) contained 43.33% male progeny. From these results it is suggested that either 50 mg/kg or 60 mg/kg of MT with a feeding period of 30 days could be considered as an optimum dose for masculinization of tilapia (O. niloticus).