Update of scientific observations of white marlin (kajikia albida) in the spanish surface longline fishing fleet targeting swordfish in the Atlantic in the period 1993-2018

A description of 1710 individuals recorded as white marlin during the period 1993-2018 is presented. 21% of the fishing sets were positive for the capture of at least one specimen for those areas considered. The overall prevalence of this species over all fish species combined was 0.65% in number and 0.52% in weight. The overall prevalence over Istiophoridae was 25.12% and 12.61% in number and weight, respectively. A discussion on the applicability of these values is included. Sizes were between 95 and 285 cm LJFL but catches of individuals smaller than 145 cm are very rare. The overall sex-ratio of females was 42.5%. Sex-ratio at size indicates an increase in the percentage of females in sizes larger than 165 cm. Only 7 females of the total 170 females with gonads analyzed presented a high gonadosomatic index. Overall nominal CPUE in weight was higher for males (2.70 kg DW/1000 hooks) than females (1.81 kg DW/1000 hooks). For the whole period analyzed, 16.3% of the specimens observed were discarded and 7.5% were released alive, although different patterns can be discerned over time

Standardized yields of the white marlin (kajikia albida) and the roundscale spearfish (tetrapturus georgii) caught as bycatch of the spanish surface longline fishery targeting swordfish (xiphias gladius) in the atlantic ocean

Standardized yields of Kajikia albida and Tetrapturus georgii were obtained from 27,481 recorded trips (887.86 x106 hooks) by the surface longline fleet targeting swordfish in the fishing areas of the Atlantic during the period 1988-2017. The observations represent about 95% of the total fishing effort of this fleet during the combined period. Roughly 4.64% of the trips recorded showed a positive catch of these species. Because of their low prevalence in this fishery, the standardized yields were calculated using a Generalized Linear Mixed Model, assuming a delta-lognormal error distribution. An overall flat trend was predicted for the whole period considered, with some annual fluctuations. The very low values predicted for the last three years were caused by the implementation of drastic domestic regulations. Some other considerations are also discussed, such as a high inter-annual variability, considered biologically unlikely, and uncertainty in the data, possibly caused by factors such as dead discards, live releases, species misidentification and current regulations

UPDATED STANDARDIZED CATCH RATES FOR SOUTH ATLANTIC STOCK OF SWORDFISH (Xiphias gladius) FROM THE SPANISH LONGLINE FLEET FOR THE PERIOD 1989-2019

Updated standardized catch rates in number and in weight were obtained using General Linear Modeling (GLM) procedures from trips carried out by the Spanish surface longline fleet targeting swordfish in the South Atlantic stock during the period 1989-2019. The criteria used to define factors were similar to those used in previous contributions. The results explained 65% and 71% of CPUE variability in number and weight, respectively, pointing to very stable standardized CPUE and mean weight trends over time. The statistical diagnoses were highly satisfactory

Size distribution of porbeagle (lamna nasus) inferred from a data

A total of 5,136 size observations of porbeagle were recovered for the period 1987-2017. The GLM results explained very moderately the variability of the sizes considering three main factors, suggesting minor but significant differences in some cases especially for the year factor and non-significant differences in other factors depending on the analysis. The greatest differences in the standardized mean length between some zones were caused by some large fish of unidentified sex. The standardized mean length data for the northern zones showed stability throughout the time series, very stable range of mean values and very few differences between sexes. The size distribution for northern areas indicated an FL-overall mean of 158 cm. The size showed a normal distribution confirming that a small fraction of individuals of this stock/s is available in the oceanic areas where the North Atlantic fleet is regularly fishing and the fishes are not fully recruited to those areas and / or this fishing gear up to 160 cm. The data suggests that some individuals could sporadically reach some intertropical areas of the Atlanti

Standardized catch rates for the blue shark (Prionace glauca) caught by the Spanish surface longline fleet in the Indian ocean during the 2001-2013 period

Standardized catch per unit of effort (CPUE) were obtained for the blue shark stock (Prionace glauca) of the Indian Ocean using General Lineal Models (GLM) from a total of 1838 trips of the Spanish surface longline fleet fishing swordfish during the 2001-2013 period. A base-case and two sensibility runs were conducted. The main factors considered into the base-case were year, area, quarter, gear and ratio between swordfish and blue shark catches. The significant base-case model explained the 82% of the CPUE variability of the blue shark. A major part of this variability was explained by the proxy of the targeting criteria defined as the ratio between the two more prevalent species caught during the trip, the swordfish and the blue shark. Other factors were also significant but less important. The standardized CPUE trend obtained in the base-case suggests a stable trend over time of the Indian Ocean blue shark stock. The sensitivity analyses showed similar trend as the base-case but in one of this runs the general trend obtained was slightly more optimistic when the ratio factor is excluded from the model.En prens

Standardized catch rates in biomass for the stock of the North Atlantic blue shark (Prionace glauca) caught by the Spanish surface longline fleet in the period 1997-2013

Standardized catch rates per unit of effort (CPUE) were obtained for the stock of the North Atlantic blue shark (Prionace glauca) using General Lineal Models (GLM) for a total of 5639 trips of the Spanish surface longline fleet targeting swordfish, during the 1997-2013 period. The main factors considered were year, area, quarter, gear and ratio between swordfish and blue shark catches. The significant model explained the 84% of CPUE variability in blue shark. A major part of this variability was explained by the proxy of the targeting criteria, shown as the ratio between the two most prevalent species caught during the trip; swordfish and blue shark. Gear was identified as the second most important factor. Other factors were also significant, but less important. The standardized CPUE trend obtained suggests a stable trend of the North Atlantic blue shark stock and differs substantially from the nominal CPUE trends observed during the period considered.En prensa0,000

Standardized yields of the blue marlin (makaira nigricans) caught as bycatch of the spanish surface longline fishery targeting swordfish (xiphias gladius) in the indian ocean

Standardized yields of blue marlin were obtained from 1,914 recorded trips (65.1*106 hooks) by the surface longline fleet targeting swordfish in the fishing areas of the Indian Ocean during the period 2003-2017. The observations represent about 90% of the total fishing effort of this fleet during this combined period. Roughly 7% of the trips recorded during this period showed a positive catch of these species (at least one fish). However a part of the observation analyzed were obtained during scientific surveys done in warmer areas where occurrence of this species is more likely but in which the fishing activity was sporadic and it is not currently carried out. Because of the low occurrence and prevalence of this species in this fishery, the standardized yields were calculated using a Generalized Linear Mixed Model, assuming a delta-lognormal error distribution. An overall flat trend was predicted for the whole period considered, with some annual fluctuations. Some other considerations are also discussed

STANDARDIZED AGE-SPECIFIC CATCH RATES IN NUMBER OF FISH FOR THE NORTH ATLANTIC SWORDFISH (Xiphias gladius) INFERRED FROM DATA OF THE SPANISH LONGLINE FLEET DURING THE PERIOD 1982-2019

Standardized ages specific 1-5+ catch rates in number of fish were updated for a period of 38 years using log-normal General Linear Model (GLM) from 11,842 trips (145,294 fishing days, 262.8 x106 hooks) of the Spanish surface longline targeting swordfish in the North Atlantic stock. The models took into consideration factors such as gear-style and a target variable to allow for the two most important changes in fishing strategy in recent periods. The base case models explained between 41%-46% of CPUE variability. The standardized CPUE for age 1 suggests a very positive phase of recruitments between periods 1997-2012 and also 1997-2019 with an overall mean of around double the relative abundance compared to the 1982-1996 mean level. This positive phase had positive effects on other ages including ages 5+ and the subsequent demographic changes since mid-1990s onwards which could be the main cause for explaining different availabilities by size and age and different average weights and overall CPUEs between different regions-fleets

Standardized catch rates in biomass for the blue shark (Prionace glauca) caught by the Spanish longline fleet in the south Atlantic during the period 1997-2013

Standardized catch rates per unit of effort (CPUE) were obtained for the stock of the South Atlantic blue shark (Prionace glauca) using General Lineal Models (GLM) for a total of 4027 trips of the Spanish surface longline fleet targeting swordfish, during the 1997-2013 period. The main factors considered were year, area, quarter, gear and ratio between swordfish and blue shark catches. The significant model explained the 87% of CPUE variability in blue shark. A major part of this variability was explained by the targeting criteria and the gear style. Other factors were also significant, but less important. The standardized CPUE obtained suggests a stable trend of the South Atlantic blue shark stock and differs substantially from the nominal CPUE trends observed during the period consideredEn prensa0,000

Standardized yields of the sailfish (istiophorus platypterus) caught as bycatch of the spanish surface longline fishery targeting swordfish (xiphias gladius) in the indian ocean

Standardized yields of sailfish were obtained from 1,914 recorded trips (65.1*106 hooks) by the surface longline fleet targeting swordfish in the fishing areas of the Indian Ocean during the period 2003-2017. The observations represent about 90% of the total fishing effort of this fleet during this combined period. Roughly 50% of the trips recorded during this period showed a positive catch of these species (at least one fish). Because of the relatively low prevalence of this species in this fishery, the standardized yields were calculated using a Generalized Linear Mixed Model, assuming a delta-lognormal error distribution. An overall flat trend was predicted for the whole period considered, with some annual fluctuations. Some other considerations are also discussed