STANDARDIZED CATCH RATES OF SAILFISH (ISTIOPHORUS ALBICANS) CAUGHT AS BYCATCH OF THE SPANISH SURFACE LONGLINE FISHERY TARGETING SWORDFISH (XIPHIAS GLADIUS) IN THE ATLANTIC OCEAN

Standardized catch rates of the sailfish (Istiophorus albicans) were obtained from 10615 trip observations of surface longline fishing targeting swordfish during the period 2001-2014. In roughly 28% of these trips at least one individual belonging to this species was found. Because of the low prevalence of this species in this fishery, the standardized CPUE was developed using a Generalized Linear Mixed Model assuming a delta-lognormal error distribution. The results obtained indicate that the overall trend of the standardized CPUE was similar for the total Atlantic areas and for the East and West stocks. An overall increasing trend was identified for the total Atlantic areas and for the East and West stock for the whole 2001-2014 period with some fluctuations in the most recent years

Reproductive activity of swordfish Xiñhias gladius, in the Atlantic Ocean inferred on the basis of macroscopic indicators

Regions with intense maturation-reproduction processes versus other regions showing less frequent, sporadic and non-existent maturation events were characterized on the basis of the gonadal index of 18,279 female swordfish. Females larger than 145 cm lower jaw-fork length (LJFL) may present high or low gonadal index values depending on the region and season. The highest gonadal indices were observed mostly in areas having Sea Surface Temperature (SST) ranging between 24°-29°C. However, the reproductive activity of females appears to be mainly restricted to the warmer epipelagic layers of the western regions with a deeper thermocline. The size at first maturity of females (LJFL50) was estimated at 146.5 cm LJFL and the maturity function was pm= 1 / (1 + e(-0.1398 (LJFL-146.5))). Qualitative maturity indicators of females support the results obtained using gonadal indices. According to catch rate data by size, sex and region, the presence of males 125- 165 cm LJFL would account for the high prevalence of males in regions where the most intense reproductive processes were observed. The characteristic ‘spawning’ related sex-ratio at size patterns are explained by thi s positive anomaly in these regions favouring males in a ratio up to 9 or 11 times greater than the abundance of females within the same medium size range. The complex reproductive process of this species would point to the practice of courting rituals, which would explain the migratory pattern of this species and its stratification by area-size-sex.Postprint0,604

Note on the observation of recruits of blue shark, Prionace glauca, in near coastal areas of Galicia (NW Spain) during the summer of 2013

This note presents a summary of several observations reported during the summer of 2013 regarding the presence of blue shark recruits in near coastal surface waters of NW Galicia, Spain. Although these observations may be considered incidental, they do, however, serve to change the general perception that this oceanic species does not reach littoral zones. Appearances of this species may be sporadic, taking place during particular years or life stages or at very specific times of the year. On the other hand, the presence of recruits in the coastal waters of Galicia during the summer –a sporadic occurrence well known by professional fishers- and the very near coastal observations reported in 2013 suggest that these areas might be a part of the nursery-recruitment grounds of blue shark in the NE Atlantic. This has been observed in other zones of the NE Atlantic where recruits or juvenile have been known to actively seek feeding grounds in areas of upwelling and high productivity during the summer period

Marine turtle encounters in the surface longline fishery in North Atlantic areas: 10º-30º N / 15º-35º W

This paper describes encounters of five species of marine turtles (C. caretta, D. coriacea, L. olivacea, L. kempii, C. mydas) observed during surface longline fishery in North Atlantic areas (10º-30º N / 15º-35º W) in the 1997-2012 period. A total of 544982 hooks were analyzed; 7.5% came from an experimental cruise which had purposely selected this zone to test the effect of different hook and bait types on bycatch rates of marine turtles. The remainder observations were obtained during routine commercial fishing operations. A total of 438 encounters with marine turtles were recorded over the course of these years, either because the animals bit the bait-hook or because they became entangled in the branchlines. Of these, 89% were released alive. The interaction and mortality rates for species, areas and years combined were 8.0E-04 and 9.0E-05 individuals per hook, respectively. These rates were, however, lower when only recordings from regular commercial fishing were considered. It should not be assumed that the resulting rates are representative of or can be extrapolated to other fishing zones.Postprint0,000

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 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

STANDARDIZED CATCH RATES FOR THE SWORDFISH (Xiphias gladius) CAUGHT BY THE SPANISH LONGLINE IN THE INDIAN OCEAN DURING THE 2001-2012 PERIOD

Standardized catch rates in weight were updated using General Linear Modeling from scientific records of the Spanish surface longline targeting swordfish in the Indian Ocean over the period 2001-2012. The base case run and several sensitivity runs were conducted for comparison with previous analyses. The main factors used for modeling were year, area, time, gear style and ratio. Different area stratifications, time criteria and other factors were considered in 6 tested runs. The models explained up to 53% of the CPUE variability. Base case and sensitivity trials for the whole Indian Ocean have shown similar CPUE trends over time. A first period from 2001 to 2007 with an overall decreasing trend in the standardized CPUE indices was predicted by all models followed by a second recovery period from 2007 to 2010 and a third period exhibiting a stable trend from 2010 to 2012. The analyses restricted to the SW regions are also consistent with each another, suggesting a decrease during the first period, an important increase during the second period and stabilization during the third period, with the most recent year reaching levels similar to those predicted for the initial period of the time series