Vasconcelos, J., M. Afonso-Dias & G. Faria 2012. Atlantic chub mackerel (Scomber colias) spawning... more Vasconcelos, J., M. Afonso-Dias & G. Faria 2012. Atlantic chub mackerel (Scomber colias) spawning season, size and age at first maturity in Madeira waters. Arquipelago. Life and Marine Sciences 29: 43-51. The pelagic chub mackerel, Scomber colias Gmelin, 1789 is one of the most important fishery resources in the Madeira Archipelago. S. colias is caught by a small and coastal purse-seine fleet that traditionally operates around the islands. Monthly samples of chub mackerel were taken from commercial landings, between January 2002 and December 2005. Sex and maturity were assigned by visually inspecting the gonads of 1998 males (17.4-46.0 cm total length, TL; 0-5 yr) and 2108 females (18.0-41.2 cm TL; 0-4 yr) using a five-stages macroscopic maturity scale; 99 specimens with undetermined sex (13.0-26.8 cm TL; 0 yr) were also sampled. The analysis of monthly gonadosomatic indices and maturity stages proportions showed that gonad development started slowly in July-August and increased in ...
A total of 206 Centrophorus squamosus (Bonnaterre, 1788) with a total length ranging from 89 to 1... more A total of 206 Centrophorus squamosus (Bonnaterre, 1788) with a total length ranging from 89 to 146 cm were captured at an average depth of 1200 metres. Of the 61 females sampled, 34% were gravid, showing an absolute individual fecundity of two to ten embryos (pups). The results clearly indicated that this deepwater shark spawns in the Portuguesewaters off Madeira archipelago.
The Atlantic chub mackerel, Scomber colias Gmelin, 1789, is one of the main fisheries resources o... more The Atlantic chub mackerel, Scomber colias Gmelin, 1789, is one of the main fisheries resources of Madeira Island. It is caught by a small and coastal purse-seine fleet that traditionally operates around the island. From January 2002 to December 2003, monthly samples of chub mackerel were collected from landings by this commercial fishing fleet. A total of 2212 sagitta otoliths were extracted for age readings from 1068 males (17.4-41.7 cm total length, TL), 1066 females (18.0-41.2 cm TL) and 78 undetermined (13.0-26.8 cm TL). A single reader aged the fishes using surface-read whole otoliths aiming to build annual age-length keys. Age readings precision and reader consistency were assessed by using the average percentage error index (APE ≤ 1.52). Ages were validated up to 4 years using marginal analyses. Estimated mean lengths at age and length von Bertalanffy growth curve parameters , estimated by non-linear methods, showed no significant differences (p>0.05) between sexes (L ∞ =...
A METHODOLOGY FOR THE MONITORING AND MANAGEMENT OF TRAWL FISHERIES IN PORTUGAL. THE SIG EXAMPLE O... more A METHODOLOGY FOR THE MONITORING AND MANAGEMENT OF TRAWL FISHERIES IN PORTUGAL. THE SIG EXAMPLE OF GEOCRUST 1.0. This paper aims to present the Geographical Information System GEOCRUST 1.0, a computer programme developed within the fishery research project DGXIV 99/059, Use of Satellite GPS data to map effort and landings of the Portuguese crustacean fleet (GEOCRUST), in the University of Algarve. This stand-alone application was developed essentially to map fishing effort and catch per unit effort (CPUE) information for the Portuguese crustacean trawl fleet, operating off the Southwest and South coasts of Portugal. The data available for this study included GPS vessels’ geographical positions and speed, transmitted via satellite to the Portuguese fisheries inspection authorities, and their catch reported to the Portuguese Directorate-General of Fisheries. GEOCRUST 1.0 was developed in ®VISUAL BASIC 6.0 using two ActiveX control: ADODB, to connect with the ®MSACCESS 2000 database an...
The Atlantic chub mackerel, Scomber colias Gmelin, 1789, is one of the main fisheries re-sources ... more The Atlantic chub mackerel, Scomber colias Gmelin, 1789, is one of the main fisheries re-sources of Madeira Island. It is caught by a small and coastal purse-seine fleet that tradi-tionally operates around the island. From January 2002 to December 2003, monthly sam-ples of chub mackerel were collected from landings by this commercial fishing fleet. A to-tal of 2212 sagitta otoliths were extracted for age readings from 1068 males (17.4-41.7 cm total length, TL), 1066 females (18.0-41.2 cm TL) and 78 undetermined (13.0-26.8 cm TL). A single reader aged the fishes using surface-read whole otoliths aiming to build annual age-length keys. Age readings precision and reader consistency were assessed by using the average percentage error index (APE ≤ 1.52). Ages were validated up to 4 years using mar-ginal analyses. Estimated mean lengths at age and length von Bertalanffy growth curve pa-rameters, estimated by non-linear methods, showed no significant differences (p>0.05) be-tween sexes ...
A dedicated GIS to estimate and map fishing effort and landings for the Portuguese crustacean tra... more A dedicated GIS to estimate and map fishing effort and landings for the Portuguese crustacean trawl fleet
There is ag reat lack of information on the e ects of boat operations on sperm whales ( Physeter ... more There is ag reat lack of information on the e ects of boat operations on sperm whales ( Physeter macrocephalus), which is the target species of the recent whale-watching industry in the Archipelago of the Azores. During the 1998 Azorean whale-watching season, between 4J une and 23 September, observations were carried-out from land-based lookouts and at sea from whale-watching boats to quantify short-term reactions of sperm whales to the presence and manoeuvres of boats. Results from landbased observations did not indicate changes in the behaviour of sperm whales, either due to the presence of boats or when exposed to inappropriate boat manoeuvres (as designated by proposed Azorean legislation). From boat-based observations, change in the whale’s speed and the presence of aerial displays were significantly more frequent when facing inappropriate boat manoeuvres. The presence of swimmers also led to ah igher frequency of aerial displays by whales. In the presence of boats, mature fema...
ABSTRACT Trawling is the most fuel-intensive fishing activity, with trawlers constituting the fle... more ABSTRACT Trawling is the most fuel-intensive fishing activity, with trawlers constituting the fleet segment most affected by the high volatility of the fuel prices. This is likely to be a main driver for adopting fuel consumption reduction strategies, which may be related to alternative fishing practices. In this study, individual vessel trajectories obtained from Vessel Monitoring System (VMS) data processed by GIS software (GeoCrust 2.0) are used to characterize a number of operational and economical parameters, for different landing profiles, corresponding to fishing trip types with specific landings composition. This information is combined with fuel consumption estimates derived from a mathematical model for the distinct phases of a round fishing trip, providing an insight into the profitability of fishing operations.
The ActiveX control MapObjects 2.0 Pro was used, within a specific application, to map, edit and ... more The ActiveX control MapObjects 2.0 Pro was used, within a specific application, to map, edit and analyse GPS data transmitted via satellite by the Portuguese crustacean trawl fleet, every 10 minutes. The MapObjects 2.0 Pro was used, instead of ArcView, because it allows data editing, while spatially displayed, with an immediate database update (implemented with Access 2000). The developed application
Vasconcelos, J., M. Afonso-Dias & G. Faria 2012. Atlantic chub mackerel (Scomber colias) spawning... more Vasconcelos, J., M. Afonso-Dias & G. Faria 2012. Atlantic chub mackerel (Scomber colias) spawning season, size and age at first maturity in Madeira waters. Arquipelago. Life and Marine Sciences 29: 43-51. The pelagic chub mackerel, Scomber colias Gmelin, 1789 is one of the most important fishery resources in the Madeira Archipelago. S. colias is caught by a small and coastal purse-seine fleet that traditionally operates around the islands. Monthly samples of chub mackerel were taken from commercial landings, between January 2002 and December 2005. Sex and maturity were assigned by visually inspecting the gonads of 1998 males (17.4-46.0 cm total length, TL; 0-5 yr) and 2108 females (18.0-41.2 cm TL; 0-4 yr) using a five-stages macroscopic maturity scale; 99 specimens with undetermined sex (13.0-26.8 cm TL; 0 yr) were also sampled. The analysis of monthly gonadosomatic indices and maturity stages proportions showed that gonad development started slowly in July-August and increased in ...
A total of 206 Centrophorus squamosus (Bonnaterre, 1788) with a total length ranging from 89 to 1... more A total of 206 Centrophorus squamosus (Bonnaterre, 1788) with a total length ranging from 89 to 146 cm were captured at an average depth of 1200 metres. Of the 61 females sampled, 34% were gravid, showing an absolute individual fecundity of two to ten embryos (pups). The results clearly indicated that this deepwater shark spawns in the Portuguesewaters off Madeira archipelago.
The Atlantic chub mackerel, Scomber colias Gmelin, 1789, is one of the main fisheries resources o... more The Atlantic chub mackerel, Scomber colias Gmelin, 1789, is one of the main fisheries resources of Madeira Island. It is caught by a small and coastal purse-seine fleet that traditionally operates around the island. From January 2002 to December 2003, monthly samples of chub mackerel were collected from landings by this commercial fishing fleet. A total of 2212 sagitta otoliths were extracted for age readings from 1068 males (17.4-41.7 cm total length, TL), 1066 females (18.0-41.2 cm TL) and 78 undetermined (13.0-26.8 cm TL). A single reader aged the fishes using surface-read whole otoliths aiming to build annual age-length keys. Age readings precision and reader consistency were assessed by using the average percentage error index (APE ≤ 1.52). Ages were validated up to 4 years using marginal analyses. Estimated mean lengths at age and length von Bertalanffy growth curve parameters , estimated by non-linear methods, showed no significant differences (p>0.05) between sexes (L ∞ =...
A METHODOLOGY FOR THE MONITORING AND MANAGEMENT OF TRAWL FISHERIES IN PORTUGAL. THE SIG EXAMPLE O... more A METHODOLOGY FOR THE MONITORING AND MANAGEMENT OF TRAWL FISHERIES IN PORTUGAL. THE SIG EXAMPLE OF GEOCRUST 1.0. This paper aims to present the Geographical Information System GEOCRUST 1.0, a computer programme developed within the fishery research project DGXIV 99/059, Use of Satellite GPS data to map effort and landings of the Portuguese crustacean fleet (GEOCRUST), in the University of Algarve. This stand-alone application was developed essentially to map fishing effort and catch per unit effort (CPUE) information for the Portuguese crustacean trawl fleet, operating off the Southwest and South coasts of Portugal. The data available for this study included GPS vessels’ geographical positions and speed, transmitted via satellite to the Portuguese fisheries inspection authorities, and their catch reported to the Portuguese Directorate-General of Fisheries. GEOCRUST 1.0 was developed in ®VISUAL BASIC 6.0 using two ActiveX control: ADODB, to connect with the ®MSACCESS 2000 database an...
The Atlantic chub mackerel, Scomber colias Gmelin, 1789, is one of the main fisheries re-sources ... more The Atlantic chub mackerel, Scomber colias Gmelin, 1789, is one of the main fisheries re-sources of Madeira Island. It is caught by a small and coastal purse-seine fleet that tradi-tionally operates around the island. From January 2002 to December 2003, monthly sam-ples of chub mackerel were collected from landings by this commercial fishing fleet. A to-tal of 2212 sagitta otoliths were extracted for age readings from 1068 males (17.4-41.7 cm total length, TL), 1066 females (18.0-41.2 cm TL) and 78 undetermined (13.0-26.8 cm TL). A single reader aged the fishes using surface-read whole otoliths aiming to build annual age-length keys. Age readings precision and reader consistency were assessed by using the average percentage error index (APE ≤ 1.52). Ages were validated up to 4 years using mar-ginal analyses. Estimated mean lengths at age and length von Bertalanffy growth curve pa-rameters, estimated by non-linear methods, showed no significant differences (p>0.05) be-tween sexes ...
A dedicated GIS to estimate and map fishing effort and landings for the Portuguese crustacean tra... more A dedicated GIS to estimate and map fishing effort and landings for the Portuguese crustacean trawl fleet
There is ag reat lack of information on the e ects of boat operations on sperm whales ( Physeter ... more There is ag reat lack of information on the e ects of boat operations on sperm whales ( Physeter macrocephalus), which is the target species of the recent whale-watching industry in the Archipelago of the Azores. During the 1998 Azorean whale-watching season, between 4J une and 23 September, observations were carried-out from land-based lookouts and at sea from whale-watching boats to quantify short-term reactions of sperm whales to the presence and manoeuvres of boats. Results from landbased observations did not indicate changes in the behaviour of sperm whales, either due to the presence of boats or when exposed to inappropriate boat manoeuvres (as designated by proposed Azorean legislation). From boat-based observations, change in the whale’s speed and the presence of aerial displays were significantly more frequent when facing inappropriate boat manoeuvres. The presence of swimmers also led to ah igher frequency of aerial displays by whales. In the presence of boats, mature fema...
ABSTRACT Trawling is the most fuel-intensive fishing activity, with trawlers constituting the fle... more ABSTRACT Trawling is the most fuel-intensive fishing activity, with trawlers constituting the fleet segment most affected by the high volatility of the fuel prices. This is likely to be a main driver for adopting fuel consumption reduction strategies, which may be related to alternative fishing practices. In this study, individual vessel trajectories obtained from Vessel Monitoring System (VMS) data processed by GIS software (GeoCrust 2.0) are used to characterize a number of operational and economical parameters, for different landing profiles, corresponding to fishing trip types with specific landings composition. This information is combined with fuel consumption estimates derived from a mathematical model for the distinct phases of a round fishing trip, providing an insight into the profitability of fishing operations.
The ActiveX control MapObjects 2.0 Pro was used, within a specific application, to map, edit and ... more The ActiveX control MapObjects 2.0 Pro was used, within a specific application, to map, edit and analyse GPS data transmitted via satellite by the Portuguese crustacean trawl fleet, every 10 minutes. The MapObjects 2.0 Pro was used, instead of ArcView, because it allows data editing, while spatially displayed, with an immediate database update (implemented with Access 2000). The developed application
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