INTERACTION BETWEEN SEABIRDS AND THE SPANISH SURFACE LONGLINE FISHERY TARGETING SWORDFISH IN THE SOUTH ATLANTIC OCEAN (SOUTH OF 25ºS) DURING THE PERIOD 2010-2014

A total of 92 sets (132,268 hooks) targeting swordfish between years 2010-2014 in the South Atlantic (Lat ≥ 25ºS) were analyzed. Various baits were used for night setting with monofilament longlines. No interaction with seabirds was detected and the interaction was therefore nil. The night setting, low levels of lighting during fishing operations and the type of fishing conducted were identified as the most important factors to explain the lack of interaction with seabirds. Observations of seabirds were also made during the study. Most sightings occurred during daytime sailing. During some operations when vessels were setting or hauling there were sporadic sightings of the spectacled petrel (Procellaria conspicillata) and the occasional albatross, although no interaction with fishing operations occurred. The species most often seen was the spectacled petrel (Procellaria conspicillata), with groups at over 150 individuals. Other species observed were Calonectris diomedea, various types of storm petrels, and other species such as Hydrobates leucorhous, Thalassarche chlororhynchos, Diomedea exulans and very rarely Thalassarche melanophrys

Standardized catch rates of shortfin mako (isurus oxyrinchus) caught by the spanish surface longline fishery targeting swordfish in the indian ocean during the period 2001-2018

Standardized catches per unit of effort in number and weight were obtained for the shortfin mako (Isurus oxyrinchus) using General Linear Modeling procedures based on trip data from the Spanish surface longline fleet targeting swordfish in the Indian Ocean over the period 2001-2018. Factors such as area, quarter, gear and bait, as well as the fishing strategy were taken into account. The model explained 31% and 24% of CPUE variability in number and weight, respectivel

UPDATED STANDARDIZED CATCH RATES IN BIOMASS FOR THE BLUE SHARK (PRIONACE GLAUCA) CAUGHT BY THE SPANISH SURFACE LONGLINE FLEET IN THE INDIAN OCEAN DURING THE 2001-2019 PERIOD

This paper provides an update of standardized catch rates in weight of blue shark using a Generalized Linear Model (GLM) from a total of 2,301 trips carried out by the Spanish surface longline fleet targeting swordfish in the Indian Ocean during the 2001-2019 period. The criteria used to define explanatory variables were similar to those used in previous papers. The main factors considered in the analysis were year, quarter, area, ratio, gear and the interaction quarter*area. The results indicate that the ratio factor (an indicator of target criteria of the skippers) defined as the ratio between the two most prevalent species caught -swordfish and blue shark- was the most important factor which explained the CPUE variability. The GLM results explained 80% of CPUE variability in weight. The index showed a stable trend over time

UPDATED STANDARDIZED CATCH RATES OF SWORDFISH (Xiphias gladius) CAUGHT BY THE SPANISH SURFACE LONGLINE FLEET IN THE INDIAN OCEAN DURING THE 2001-2018 PERIOD

Standardized catch rates of the Spanish surface longline fleet targeting swordfish are provided for the period 2001-2018. Generalized Linear Models (GLM) log-normal were used to update standardized catch rates in number of fish and in weight. Factors such as area, quarter, gear and bait, as well as the fishing strategy (based on the ratio between the most prevalent species and that appreciated most by skippers) were taken into account. The model explained 54% and 57% of CPUE variability in number and weight, respectively

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

PLAUSIBILITY AND UNCERTAINTY OF BASIC DATA AND PARAMETER SELECTION ON STOCK ASSESSMENTS: A REVIEW OF SOME INPUT DATA USED IN THE 2017 ASSESSMENT OF THE SHORTFIN MAKO (ISURUS OXYRINCHUS) OF THE NORTHERN ATLANTIC STOCK

Three key-elements for the case of shortfin mako used in 2017 assessment of North Atlantic stock are reviewed. The catch scenarios implemented indicate that historical T1 considered in base case scenario (C1) have greatly underestimated the level of catches during several of the initial decades, taking into consideration the history of the fisheries, fleet’s capacity and fishing effort by fleet. A hypothetical catch scenario also used (C2) probably overestimated in an important amount the catch levels of some fleets and fleets combined for the most recent period of that series. The review of CPUE series suggests that there may be qualitative and/or quantitative limitations in some of them which would likely affect some series being considered as indicators of abundance. Some key biological parameters considered in the assessment are also reviewed and discussed, such as the growth model implemented and the age of first reproduction of the females, within a context compared to other studies, preliminary estimations from tagging-recapture data and those parameters applied in other stock of the same specie, and in other species from the same family

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

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