C. Needle - Academia.edu (original) (raw)

Papers by C. Needle

Research paper thumbnail of Incorporating time-series structure in medium-term recruitment projections

Research paper thumbnail of Implications of a warming North Sea for the growth of haddock Melanogrammus aeglefinus

Journal of Fish Biology, 2011

The present study aimed firstly, to test for a temperature effect on North Sea haddock Melanogram... more The present study aimed firstly, to test for a temperature effect on North Sea haddock Melanogrammus aeglefinus growth and secondly, to develop a model that could be used to assess total length (L(T)) and mass (M)-at-age response to different temperature scenarios. The von Bertalanffy growth model was fitted on a cohort-by-cohort basis from 1970 to 2006. The asymptotic L(T) (L(∞)) was negatively correlated with temperature while the rate at which L(∞) is reached (K) was positively correlated with temperature. K was negatively correlated with density, whereas no effect on L(∞) was observed. These effects were incorporated into a von Bertalanffy model which was extended to include temperature and density as explanatory variables. Only the temperature variable was significant. Fitting the extended von Bertalanffy model revealed that L(∞) decreased while K increased with increasing temperature, resulting in up to a 40% loss of individual yield at older ages. The dramatic decline observed in the mean age at which 50% of the population becomes mature suggests that higher temperatures resulted in larger young M. aeglefinus that matured earlier and therefore reached a smaller maximum size. In a global warming context, the loss of individual yield observed at old ages is likely to reduce the fisheries yield for M. aeglefinus in the North Sea.

Research paper thumbnail of Evaluating the effect of real-time closures on cod targeting

ICES Journal of Marine Science, 2011

ABSTRACT Under its Conservation Credits scheme to reduce cod mortality, the Scottish Government h... more ABSTRACT Under its Conservation Credits scheme to reduce cod mortality, the Scottish Government has implemented a system of real-time closures (RTCs) since 2008. These are relatively small, temporarily closed areas (50-225 square nautical miles per RTC, closed for 21 d) that are triggered by high cod catches. An important step in evaluating their effectiveness is to determine the response of vessels to RTCs, because the conservation benefit would be reduced if vessels moved to areas of greater cod abundance following closures. Abundance indices from research-vessel surveys and commercial-vessel observer trips are combined to create a time-and space-dependent relative cod-importance index (RCII). Vessel monitoring system data from Scottish vessels fishing during 2008/2009 are used to construct RCII profiles for each vessel, which are then used to determine whether the areas to which vessels move have a higher or a lower RCII, and how far away they move when an RTC is activated. We show that the RCII of the areas moved to tends to be lower than that of the RTC and that vessels travel farther when moving away from a closure than when moving back after reopening. Although not conclusive, this result indicates that RTCs may impact beneficially on cod mortality.

Research paper thumbnail of Using survey data independently from commercial data in stock assessment: an example using haddock in ICES Division VIa

ICES Journal of Marine Science, 2005

Research paper thumbnail of The human drivers of global land cover change: the case of forests

Hydrological Processes, 1998

The results of a new approach to the speci®cation of the relationship between deforestation and p... more The results of a new approach to the speci®cation of the relationship between deforestation and population are presented. They suggest that approximately half of the deforestation that has occurred over the long sweep of human history can be explained statistically in terms of population growth. It is cautioned, however, that serious conceptual and methodological problems confront the analysis of the relationship. It is also emphasized that the relationship is complex. Evidence is presented to show that it has changed through time, and that it is complicated by interactions between various factors operating in dierent ways at dierent levels. #

Research paper thumbnail of The relationships of population and forest trends

The Geographical Journal, 2000

The relationship between national trends in forest area and population is reviewed at the global ... more The relationship between national trends in forest area and population is reviewed at the global scale. Evidence of an inverse relationship is confirmed. The relationship, however, may have weakened in recent decades, and it has clearly undergone a reversal in some countries during the nineteenth to twentieth centuries. The theme of a changing relationship through time is thus developed, as is that of an asymmetrical relationship in the sense that the forest area is likely to stabilize before population. On the basis of modelling from the current demographic relationship, the global forest area should stabilize before the middle of the twenty-first century.

Research paper thumbnail of Making the most of research vessel data in stock assessments: Examples from ICES division VIa

Data from systematic research vessel surveys can be used to model the population dynamics of comm... more Data from systematic research vessel surveys can be used to model the population dynamics of commercially important fish stocks. In Aberdeen, Fisheries Research Services (FRS) have been performing bottom-trawl surveys since the 1890s. These provide detailed information on how fish abundance, species composition and biotic parameters (such as length, maturity and sex ratios) change in space and time. Currently, however, the most commonly used methods of stock assessments (for example, virtual population analysis or VPA) rely principally on catch data from commercial fisheries; survey data are only used in calibration. VPA is thus heavily dependent on the quality of commercial catch data and subject to bias as a result of catch misreporting. Because of this, there is interest in developing fisheries-independent methods of stock assessment. The purposes of this paper are: a) to examine the quality and robustness of research vessel survey data; b) to investigate the utility of more deta...

Research paper thumbnail of Incorporating time-series structure in medium-term recruitment projections

Research paper thumbnail of Implications of a warming North Sea for the growth of haddock Melanogrammus aeglefinus

Journal of Fish Biology, 2011

The present study aimed firstly, to test for a temperature effect on North Sea haddock Melanogram... more The present study aimed firstly, to test for a temperature effect on North Sea haddock Melanogrammus aeglefinus growth and secondly, to develop a model that could be used to assess total length (L(T)) and mass (M)-at-age response to different temperature scenarios. The von Bertalanffy growth model was fitted on a cohort-by-cohort basis from 1970 to 2006. The asymptotic L(T) (L(∞)) was negatively correlated with temperature while the rate at which L(∞) is reached (K) was positively correlated with temperature. K was negatively correlated with density, whereas no effect on L(∞) was observed. These effects were incorporated into a von Bertalanffy model which was extended to include temperature and density as explanatory variables. Only the temperature variable was significant. Fitting the extended von Bertalanffy model revealed that L(∞) decreased while K increased with increasing temperature, resulting in up to a 40% loss of individual yield at older ages. The dramatic decline observed in the mean age at which 50% of the population becomes mature suggests that higher temperatures resulted in larger young M. aeglefinus that matured earlier and therefore reached a smaller maximum size. In a global warming context, the loss of individual yield observed at old ages is likely to reduce the fisheries yield for M. aeglefinus in the North Sea.

Research paper thumbnail of Evaluating the effect of real-time closures on cod targeting

ICES Journal of Marine Science, 2011

ABSTRACT Under its Conservation Credits scheme to reduce cod mortality, the Scottish Government h... more ABSTRACT Under its Conservation Credits scheme to reduce cod mortality, the Scottish Government has implemented a system of real-time closures (RTCs) since 2008. These are relatively small, temporarily closed areas (50-225 square nautical miles per RTC, closed for 21 d) that are triggered by high cod catches. An important step in evaluating their effectiveness is to determine the response of vessels to RTCs, because the conservation benefit would be reduced if vessels moved to areas of greater cod abundance following closures. Abundance indices from research-vessel surveys and commercial-vessel observer trips are combined to create a time-and space-dependent relative cod-importance index (RCII). Vessel monitoring system data from Scottish vessels fishing during 2008/2009 are used to construct RCII profiles for each vessel, which are then used to determine whether the areas to which vessels move have a higher or a lower RCII, and how far away they move when an RTC is activated. We show that the RCII of the areas moved to tends to be lower than that of the RTC and that vessels travel farther when moving away from a closure than when moving back after reopening. Although not conclusive, this result indicates that RTCs may impact beneficially on cod mortality.

Research paper thumbnail of Using survey data independently from commercial data in stock assessment: an example using haddock in ICES Division VIa

ICES Journal of Marine Science, 2005

Research paper thumbnail of The human drivers of global land cover change: the case of forests

Hydrological Processes, 1998

The results of a new approach to the speci®cation of the relationship between deforestation and p... more The results of a new approach to the speci®cation of the relationship between deforestation and population are presented. They suggest that approximately half of the deforestation that has occurred over the long sweep of human history can be explained statistically in terms of population growth. It is cautioned, however, that serious conceptual and methodological problems confront the analysis of the relationship. It is also emphasized that the relationship is complex. Evidence is presented to show that it has changed through time, and that it is complicated by interactions between various factors operating in dierent ways at dierent levels. #

Research paper thumbnail of The relationships of population and forest trends

The Geographical Journal, 2000

The relationship between national trends in forest area and population is reviewed at the global ... more The relationship between national trends in forest area and population is reviewed at the global scale. Evidence of an inverse relationship is confirmed. The relationship, however, may have weakened in recent decades, and it has clearly undergone a reversal in some countries during the nineteenth to twentieth centuries. The theme of a changing relationship through time is thus developed, as is that of an asymmetrical relationship in the sense that the forest area is likely to stabilize before population. On the basis of modelling from the current demographic relationship, the global forest area should stabilize before the middle of the twenty-first century.

Research paper thumbnail of Making the most of research vessel data in stock assessments: Examples from ICES division VIa

Data from systematic research vessel surveys can be used to model the population dynamics of comm... more Data from systematic research vessel surveys can be used to model the population dynamics of commercially important fish stocks. In Aberdeen, Fisheries Research Services (FRS) have been performing bottom-trawl surveys since the 1890s. These provide detailed information on how fish abundance, species composition and biotic parameters (such as length, maturity and sex ratios) change in space and time. Currently, however, the most commonly used methods of stock assessments (for example, virtual population analysis or VPA) rely principally on catch data from commercial fisheries; survey data are only used in calibration. VPA is thus heavily dependent on the quality of commercial catch data and subject to bias as a result of catch misreporting. Because of this, there is interest in developing fisheries-independent methods of stock assessment. The purposes of this paper are: a) to examine the quality and robustness of research vessel survey data; b) to investigate the utility of more deta...