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G A Chouinard - One of the best experts on this subject based on the ideXlab platform.
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predicted extirpation of the dominant Demersal Fish in a large marine ecosystem atlantic cod gadus morhua in the southern gulf of st lawrence
Canadian Journal of Fisheries and Aquatic Sciences, 2008Co-Authors: Douglas P Swain, G A ChouinardAbstract:Atlantic cod (Gadus morhua) was the dominant Demersal Fish and most important predator in the southern Gulf of St. Lawrence ecosystem as recently as the 1980s. However, productivity of southern Gul...
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predicted extirpation of the dominant Demersal Fish in a large marine ecosystem atlantic cod gadus morhua in the southern gulf of st lawrence
Canadian Journal of Fisheries and Aquatic Sciences, 2008Co-Authors: Douglas P Swain, G A ChouinardAbstract:Atlantic cod (Gadus morhua) was the dominant Demersal Fish and most important predator in the southern Gulf of St. Lawrence ecosystem as recently as the 1980s. However, productivity of southern Gulf cod has declined, and the population is no longer viable even in the absence of Fishing. We conducted population projections taking into account uncertainty in current abundance-at-age and uncertainty or variability in each of the components of population productivity (i.e., rates of recruitment, individual growth, and adult natural mortality). We defined extirpation as a spawning stock biomass less than 1000 t (<0.3% of historical levels). Based on these projections, at its current level of productivity, this population is certain to be extirpated within 40 years in the absence of Fishing and in 20 years with Fishery removals at the level of the total allowable catch in 2007 and 2008 (2000 t). Elevated natural mortality of adult cod (M) is the main factor contributing to the low productivity of this stock. Be...
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rapid communication communication rapide predicted extirpation of the dominant Demersal Fish in a large marine ecosystem atlantic cod gadus morhua in the southern gulf of st lawrence
2008Co-Authors: Douglas P Swain, G A ChouinardAbstract:Atlantic cod (Gadus morhua) was the dominant Demersal Fish and most important predator in the southern Gulf of St. Lawrence ecosystem as recently as the 1980s. However, productivity of southern Gulf cod has declined, and the population is no longer viable even in the absence of Fishing. We conducted population projections taking into account un- certainty in current abundance-at-age and uncertainty or variability in each of the components of population productivity (i.e., rates of recruitment, individual growth, and adult natural mortality). We defined extirpation as a spawning stock bio- mass less than 1000 t (<0.3% of historical levels). Based on these projections, at its current level of productivity, this pop- ulation is certain to be extirpated within 40 years in the absence of Fishing and in 20 years with Fishery removals at the level of the total allowable catch in 2007 and 2008 (2000 t). Elevated natural mortality of adult cod (M) is the main factor contributing to the low productivity of this stock. Because M appears to be increasing, our projections are likely overly op- timistic. Resume´ : Aussi recemment que durant les annees 1980, la morue franche (Gadus morhua )etait le poisson benthique dom- inant et le plus important predateur dans l'ecosysteme du sud du Golfe Saint-Laurent. Cependant, la productivitedes mor- ues du sud du golfe a diminueet la population n'est plus viable, meme en l'absence de peche. Nous avons fait des projections demographiques qui tiennent compte de l'incertitude au sujet des abondances actuelles en fonction de l'age, ainsi que de l'incertitude ou de la variabiliteassociees a chacune des composantes de la productivitede la population (c'est-a `-dire les taux de recrutement, de croissance individuelle et de mortalitenaturelle des adultes). Nous avons defini l'extirpation comme correspondant aune biomasse du stock reproducteur inferieure a 1000 t (<0,3 % des valeurs du passe ´). D'apres ces projections, au niveau actuel de productivite ´, cette population sera certainement extirpee en moins de 40 ans en l'absence de peche et en 20 ans au rythme actuel des retraits dus ala peche correspondant a la capture totale permise en 2007 et 2008 (2000 t). La mortalitenaturelle accrue des morues adultes (M) est le facteur principal qui expli- que la faible productivitede ce stock. Comme M semble augmenter, nos projections sont vraisemblablement trop opti- mistes. (Traduit par la Redaction)
Douglas P Swain - One of the best experts on this subject based on the ideXlab platform.
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predicted extirpation of the dominant Demersal Fish in a large marine ecosystem atlantic cod gadus morhua in the southern gulf of st lawrence
Canadian Journal of Fisheries and Aquatic Sciences, 2008Co-Authors: Douglas P Swain, G A ChouinardAbstract:Atlantic cod (Gadus morhua) was the dominant Demersal Fish and most important predator in the southern Gulf of St. Lawrence ecosystem as recently as the 1980s. However, productivity of southern Gul...
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predicted extirpation of the dominant Demersal Fish in a large marine ecosystem atlantic cod gadus morhua in the southern gulf of st lawrence
Canadian Journal of Fisheries and Aquatic Sciences, 2008Co-Authors: Douglas P Swain, G A ChouinardAbstract:Atlantic cod (Gadus morhua) was the dominant Demersal Fish and most important predator in the southern Gulf of St. Lawrence ecosystem as recently as the 1980s. However, productivity of southern Gulf cod has declined, and the population is no longer viable even in the absence of Fishing. We conducted population projections taking into account uncertainty in current abundance-at-age and uncertainty or variability in each of the components of population productivity (i.e., rates of recruitment, individual growth, and adult natural mortality). We defined extirpation as a spawning stock biomass less than 1000 t (<0.3% of historical levels). Based on these projections, at its current level of productivity, this population is certain to be extirpated within 40 years in the absence of Fishing and in 20 years with Fishery removals at the level of the total allowable catch in 2007 and 2008 (2000 t). Elevated natural mortality of adult cod (M) is the main factor contributing to the low productivity of this stock. Be...
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rapid communication communication rapide predicted extirpation of the dominant Demersal Fish in a large marine ecosystem atlantic cod gadus morhua in the southern gulf of st lawrence
2008Co-Authors: Douglas P Swain, G A ChouinardAbstract:Atlantic cod (Gadus morhua) was the dominant Demersal Fish and most important predator in the southern Gulf of St. Lawrence ecosystem as recently as the 1980s. However, productivity of southern Gulf cod has declined, and the population is no longer viable even in the absence of Fishing. We conducted population projections taking into account un- certainty in current abundance-at-age and uncertainty or variability in each of the components of population productivity (i.e., rates of recruitment, individual growth, and adult natural mortality). We defined extirpation as a spawning stock bio- mass less than 1000 t (<0.3% of historical levels). Based on these projections, at its current level of productivity, this pop- ulation is certain to be extirpated within 40 years in the absence of Fishing and in 20 years with Fishery removals at the level of the total allowable catch in 2007 and 2008 (2000 t). Elevated natural mortality of adult cod (M) is the main factor contributing to the low productivity of this stock. Because M appears to be increasing, our projections are likely overly op- timistic. Resume´ : Aussi recemment que durant les annees 1980, la morue franche (Gadus morhua )etait le poisson benthique dom- inant et le plus important predateur dans l'ecosysteme du sud du Golfe Saint-Laurent. Cependant, la productivitedes mor- ues du sud du golfe a diminueet la population n'est plus viable, meme en l'absence de peche. Nous avons fait des projections demographiques qui tiennent compte de l'incertitude au sujet des abondances actuelles en fonction de l'age, ainsi que de l'incertitude ou de la variabiliteassociees a chacune des composantes de la productivitede la population (c'est-a `-dire les taux de recrutement, de croissance individuelle et de mortalitenaturelle des adultes). Nous avons defini l'extirpation comme correspondant aune biomasse du stock reproducteur inferieure a 1000 t (<0,3 % des valeurs du passe ´). D'apres ces projections, au niveau actuel de productivite ´, cette population sera certainement extirpee en moins de 40 ans en l'absence de peche et en 20 ans au rythme actuel des retraits dus ala peche correspondant a la capture totale permise en 2007 et 2008 (2000 t). La mortalitenaturelle accrue des morues adultes (M) est le facteur principal qui expli- que la faible productivitede ce stock. Comme M semble augmenter, nos projections sont vraisemblablement trop opti- mistes. (Traduit par la Redaction)
Stephen P Kirkman - One of the best experts on this subject based on the ideXlab platform.
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spatio temporal trends in diversity of Demersal Fish species in the benguela current large marine ecosystem region
Fisheries Oceanography, 2015Co-Authors: Dawit Yemane, John Kathena, Samuel K. Mafwila, Silvi E. Nsiangango, Stephen P KirkmanAbstract:Biodiversity is changing at an unprecedented rate on a global scale as a complex response to several anthropogenic changes, in addition to the background natural environmental variability and cycles. In the Benguela Current Large Marine Ecosystem region (BCLME), aspects of Demersal Fish species diversity were studied between 1985 and 2010 in three countries (Angola, Namibia, and South Africa) using scientific survey data (depending on country). The study was aimed to address multi-tiered objectives: to document patterns of diversity (as measured by the different indices of diversity) in the three countries; to relate these patterns to various explanatory variables (depth, latitude, longitude, bottom temperature, and total catch) using a generalized additive model; and to compare the patterns of diversity and importance of potential drivers of biodiversity across the BCLME region. Results showed contrasting diversity patterns between the three countries in terms of both the form and strength of the relationship with different sets of predictors. Species richness S, Pielou's evenness index J', and Shannon–Wiener index H' were shown to increase with increasing depth in all three countries. In addition, both the overall and depth-dependent latitudinal pattern in S showed local and regional level bottlenecks in biodiversity, and the latitudinal pattern of S was similar to the pattern of bottom temperature. Overall, the species richness of Demersal Fish species (S) was found to increase as one moved towards the equator, in line with similar studies that reported an increase in richness with latitude.
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assessing changes in the distribution and range size of Demersal Fish populations in the benguela current large marine ecosystem
Reviews in Fish Biology and Fisheries, 2014Co-Authors: Dawit Yemane, John Kathena, Silvi E. Nsiangango, Stephen P Kirkman, Bjorn Erik Axelsen, Toufiek SamaaiAbstract:Distributional change, expressed as range expansion or contraction , has been observed in many marine populations and related to changes in the environment. The extent of such distributional changes is also expected to increase in response to future climate change. The Benguela Current Large Marine Ecosystem (BCLME) which adjoins the south-western coast of Africa is a global marine hotspot with long-term warming occurring over a large area. The area is also an important centre of marine food production for three countries—South Africa, Namibia and Angola and is considered to be vulnerable to future climate change or increased climate variability. In this study we analysed change in distribution and range size of several Demersal Fish species in the BCLME over the period 1985–2010, including both commercial and non-commercial Fish populations. Some of the observed changes in distribution and range size correspond to what is expected with increased warming whereas others appear to the contrary. Overall the results of the study highlight the complex nature of the response of Fish population to climate change.
Dawit Yemane - One of the best experts on this subject based on the ideXlab platform.
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spatio temporal trends in diversity of Demersal Fish species in the benguela current large marine ecosystem region
Fisheries Oceanography, 2015Co-Authors: Dawit Yemane, John Kathena, Samuel K. Mafwila, Silvi E. Nsiangango, Stephen P KirkmanAbstract:Biodiversity is changing at an unprecedented rate on a global scale as a complex response to several anthropogenic changes, in addition to the background natural environmental variability and cycles. In the Benguela Current Large Marine Ecosystem region (BCLME), aspects of Demersal Fish species diversity were studied between 1985 and 2010 in three countries (Angola, Namibia, and South Africa) using scientific survey data (depending on country). The study was aimed to address multi-tiered objectives: to document patterns of diversity (as measured by the different indices of diversity) in the three countries; to relate these patterns to various explanatory variables (depth, latitude, longitude, bottom temperature, and total catch) using a generalized additive model; and to compare the patterns of diversity and importance of potential drivers of biodiversity across the BCLME region. Results showed contrasting diversity patterns between the three countries in terms of both the form and strength of the relationship with different sets of predictors. Species richness S, Pielou's evenness index J', and Shannon–Wiener index H' were shown to increase with increasing depth in all three countries. In addition, both the overall and depth-dependent latitudinal pattern in S showed local and regional level bottlenecks in biodiversity, and the latitudinal pattern of S was similar to the pattern of bottom temperature. Overall, the species richness of Demersal Fish species (S) was found to increase as one moved towards the equator, in line with similar studies that reported an increase in richness with latitude.
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assessing changes in the distribution and range size of Demersal Fish populations in the benguela current large marine ecosystem
Reviews in Fish Biology and Fisheries, 2014Co-Authors: Dawit Yemane, John Kathena, Silvi E. Nsiangango, Stephen P Kirkman, Bjorn Erik Axelsen, Toufiek SamaaiAbstract:Distributional change, expressed as range expansion or contraction , has been observed in many marine populations and related to changes in the environment. The extent of such distributional changes is also expected to increase in response to future climate change. The Benguela Current Large Marine Ecosystem (BCLME) which adjoins the south-western coast of Africa is a global marine hotspot with long-term warming occurring over a large area. The area is also an important centre of marine food production for three countries—South Africa, Namibia and Angola and is considered to be vulnerable to future climate change or increased climate variability. In this study we analysed change in distribution and range size of several Demersal Fish species in the BCLME over the period 1985–2010, including both commercial and non-commercial Fish populations. Some of the observed changes in distribution and range size correspond to what is expected with increased warming whereas others appear to the contrary. Overall the results of the study highlight the complex nature of the response of Fish population to climate change.
Silvi E. Nsiangango - One of the best experts on this subject based on the ideXlab platform.
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spatio temporal trends in diversity of Demersal Fish species in the benguela current large marine ecosystem region
Fisheries Oceanography, 2015Co-Authors: Dawit Yemane, John Kathena, Samuel K. Mafwila, Silvi E. Nsiangango, Stephen P KirkmanAbstract:Biodiversity is changing at an unprecedented rate on a global scale as a complex response to several anthropogenic changes, in addition to the background natural environmental variability and cycles. In the Benguela Current Large Marine Ecosystem region (BCLME), aspects of Demersal Fish species diversity were studied between 1985 and 2010 in three countries (Angola, Namibia, and South Africa) using scientific survey data (depending on country). The study was aimed to address multi-tiered objectives: to document patterns of diversity (as measured by the different indices of diversity) in the three countries; to relate these patterns to various explanatory variables (depth, latitude, longitude, bottom temperature, and total catch) using a generalized additive model; and to compare the patterns of diversity and importance of potential drivers of biodiversity across the BCLME region. Results showed contrasting diversity patterns between the three countries in terms of both the form and strength of the relationship with different sets of predictors. Species richness S, Pielou's evenness index J', and Shannon–Wiener index H' were shown to increase with increasing depth in all three countries. In addition, both the overall and depth-dependent latitudinal pattern in S showed local and regional level bottlenecks in biodiversity, and the latitudinal pattern of S was similar to the pattern of bottom temperature. Overall, the species richness of Demersal Fish species (S) was found to increase as one moved towards the equator, in line with similar studies that reported an increase in richness with latitude.
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assessing changes in the distribution and range size of Demersal Fish populations in the benguela current large marine ecosystem
Reviews in Fish Biology and Fisheries, 2014Co-Authors: Dawit Yemane, John Kathena, Silvi E. Nsiangango, Stephen P Kirkman, Bjorn Erik Axelsen, Toufiek SamaaiAbstract:Distributional change, expressed as range expansion or contraction , has been observed in many marine populations and related to changes in the environment. The extent of such distributional changes is also expected to increase in response to future climate change. The Benguela Current Large Marine Ecosystem (BCLME) which adjoins the south-western coast of Africa is a global marine hotspot with long-term warming occurring over a large area. The area is also an important centre of marine food production for three countries—South Africa, Namibia and Angola and is considered to be vulnerable to future climate change or increased climate variability. In this study we analysed change in distribution and range size of several Demersal Fish species in the BCLME over the period 1985–2010, including both commercial and non-commercial Fish populations. Some of the observed changes in distribution and range size correspond to what is expected with increased warming whereas others appear to the contrary. Overall the results of the study highlight the complex nature of the response of Fish population to climate change.