Ecología de la platija americana (Hippoglossoides platessoides (Fabricius, 1780)) en el Atlántico Norte

En este estudio se actualiza el conocimiento de la ecología de varias poblaciones de platija americana (Hippoglossoides platessoides), centrado en el Atlántico noroeste, en el Gran Banco y en Flemish Cap. Las principales diferencias en los parámetros biológicos que definen las características respectivas aparecen confirmadas, así como las tendencias de su evolución que han venido mostrando. Por primera vez se establece la relación entre los cambios ontogénicos y energéticos de la dieta con el crecimiento y la reproducción en estas poblaciones, y se analiza la base bioenergética que posibilita las adaptaciones del ciclo vital en cada una de ellas. Los valores de los respectivos parámetros biológicos definen diferentes adaptaciones en las estrategias vitales

Distribution of American Plaice (Hippoglossoides platesssoides) on the Grand Bank (NAFO Divisions 3NO), 1995-2004

The changes appreciated in the distribution of American plaice (Hippoglossoides platessoides) by depth on the Grand Bank (NAFO Divisions 3NO) in the period 2001-04 did not show a clear relationship with the increase of estimated biomass. Significant differences in the distribution depth range between sizes and sexes were observed. The females were distributed until deeper than the males. The small individuals (<20 cm) also appeared in the deepest strata. Inter-annual changes were appreciated in the period 2001-04 with an accused decrease in the distribution depth range in the 2004. The population was concentrated at shallower depth in spite of the increment of the abundance and biomass in the last year

Food and Feeding of Ocean Redfish (Sebastes mentella Travin) in the North Atlantic

The food and feeding of ocean redfish are described from stomach contents of 26381 individuals analyzed on board commercial vessels in the Irminger waters from March to November. Most of the stomachs had been everted (15488). The feeding intensity mean value throughout the period was 7.1%. The feeding intensity was higher in the months of least reproductive activity in each sex. The prey spectrum was narrow, the diversity diminishing in autumn and winter. Crustacea dominates the redfish diet in March. Other items show great seasonal variation also as with Mollusca which have an increased presence in summer. Crustacea were more abundant in the diet of smaller individuals, the variety of fishes preyed on increasing with the length. The occurrence of Myctop hidae remains constant throughout the length range although their volume increases with size. A marked presence of offal was observed associated with the period of intense commercial activity: April to June. The offal occurrence and offal volume increased with length, particularly in the individuals larger than 40 cm. The intense fishing activity was observed to have a direct influence on diet composition. The main natural prey were: Copepoda (IRI=1582.5); Eupahusiacea (IRI=1361.9); Mollusca Decapoda (IRI=736.8) and Myctophydae (IRI= 220.3). The comparison between Flemish Cap and Irminger Sea redfish diet populations in the same month show important composition differences. The condition factor by month values (Mean=1.26+-0.12) were less than those obtained in the Flemish Cap population (Mean 1.43+-0.17)

Atlantic Cod Population Indices Obtained from the Spring Surveys Conducted by Spain in the NAFO Regulatory Area of Divisions 3NO, 1995-2003

Since 1995, a stratified random spring bottom trawl survey in the NAFO Regulatory Area of Div. 3NO was conducted by Spain. In 2001, the trawl vessel was replaced; so, the time series indices were transformed. The transformed entire series of mean catches, abundance, biomass and length distribution for Atlantic cod are presented for the period 1995-2000, and the no-transformed data for the years 2001-2003. The standard deviations are shown for abundance and biomass. In years 1998 and 2001 some extreme catches occurred, so we present the series with and withoout those data.The summed abundance and biomass based on conversion of the lenght frequencias are presented and compared to the estimates from the method used to convert the CPUE. The results are quite the same. The biomass presents a non-clear trend and the abundance an increasing since 1998 and a decreasing last year

American Plaice Biomass and Abundance from the Surveys Conducted by Spain in the NAFO Regulatory Area of Divisions 3NO, 1995-2003

Since 1995, a stratified random spring bottom trawl survey in the NAFO Regulatory Area of Div. 3NO was conducted by Spain. In 2001, the trawl vessel was replaced; so, the time series indices was transformed. The transformed entire series of mean catches, abundance, biomass and lenght distribution for American plaice are presented for the period 1995-2000, and the no-transformed data for the years 2001-2003. The standard deviation are shown for abundance and biomass. The summed abundance and biomass based on conversion of the lenght frequencies are presented and compared to the estimates from the method used to convert the CPUE. The results from the lenght distribution are smaller in all cases. A decreasing in American plaice abundance and biomass is observed in last years (2001-2002), although this recent year an increasing occurs. A high percent of juvenile individuals shows a good recruitment in recent years

Atlantic cod and Yellowtail flounder indices from the Spanish Survey conducted in Divisions 3NO of the NAFO Regulatory Area

Since 1995, Spain carries out a stratified random spring bottom trawl survey in Div. 3NO of the NAFO Regulatory Area. The entire series of mean catches, biomass and length distribution for Atlantic cod (Gadus morhua) are presented for the period 1997-2009 and for Yellowtail flounder (Limanda ferruginea) for the period 1995-2009. For Atlantic cod we can see a general decreasing in the biomass between 2002 and 2005, and a increasing since then, especially in 2006 and, higher, in 2009, although this values is mainly due to two hauls with high catches, In 2007 the biomass decreased, but the level is over the value in the period 2002-2005. For this species, an increase in the recruitment can be seen in 2004 and 2005, and from 2007 the youngest length classes are much over the rest of the length classes. For Yellowtail flounder, there is no a clear trend since 1998; its indices are almost constant along this period

Biomass and length distribution for Roughhead grenadier, Thorny skate and White hake from the surveys conducted by Spain in NAFO 3NO

Data for Roughhead grenadier (Macrourus berglax), Thorny skate (Amblyraja radiata) and Withe hake (Urophycis tenuis) from Spanish Spring survey are presented. The abundance and biomass were estimated for the period 1997-2010 for Roughhead grenadier and Thorny skate, and 2001-2010 for White hake. The length distribution was obtained and presented in numbers per haul stratified mean catches. The indices of Roughhead grenadier present no trend along the years until 2003, with an increase in years 2004-2006, mainly in 2004. In 2007 the biomass were on the level of 2003 value, with a slight increase since then broken with a new decrease in 2010, reaching again the level of 2007 values. Thorny skate indices starts the series with poor values, increasing constantly up to the historical maximum in 2000, following with a decrease since 2001 until 2003, increased for 2004-2006 and decreased again since 2007. For White hake, there were great catches in 2001, and a sharp decrease since then, broken in 2005 for an increase in the indices, but a new decrease reaching the minimum values of the series in 2008. In 2009 there was a sligth increase, reaching a value between the 2006 and the 2007 biomass, following with a new slight decrease in 2010. Only in 2004 we can see a good presence of individuals between 16 and 26 cm

Atlantic cod predation on redfish in Flemish Cap

The aim of this study is to estimate the predation on redfish by Atlantic cod in Flemish Cap in the period 2000- 2010 and the impact of the cod stock recovery in recent years on the prey stock. Atlantic cod samples of stomach contents were taken in the Flemish Cap survey (NAFO Div. 3M). The analysis was done jointly from all individuals, undifferentiated sexes. They were established four size groups of Atlantic cod with a different predation rate on redfish: less than 30 cm, 30-59 cm, 60-79 cm and ≥80 cm. Results show a clear increasing trend in the daily consumption of redfish by cod since 2005. Cod less than 30 cm (one year old) does not consume redfish. Cod with lengths more than 30 cm presents an increasing trend in the quantity of the redfish preyed in the analyzed period. This trend is more evident in the cod more than 60 cm, ages older than 5 years old. Redfish more than 27 cm (older than 8 years old) does not appear in the cod diet. Redfish estimated biomass consumed by total cod biomass is higher than redfish biomass estimated in the last approved assessment disappeared by natural mortality in the period 2000-2005