Use of a marine reserve to determine the direct and indirect effects of fishing on growth in a New Zealand fishery for the spiny lobster Jasus edwardsii

2012 ◽  
Vol 69 (5) ◽  
pp. 894-905 ◽  
Author(s):  
Debbie J. Freeman ◽  
Paul A. Breen ◽  
Alison B. MacDiarmid
Keyword(s):  
Growth Rates ◽  
Marine Reserve ◽  
Spiny Lobster ◽  
Catch Per Unit Effort ◽  
Density Dependent ◽  
Time Period ◽  
Jasus Edwardsii ◽  
Negative Effect ◽  
Similar Growth ◽  
Positive Effect

The effects of fishing on growth in a spiny lobster, Jasus edwardsii , were explored by using a no-take marine reserve as a control for these effects. We analysed data from lobster tag–recapture studies outside the reserve from 1975 until the present and tag–recapture from inside the reserve during a recent 8-year study. We explored whether recent and historical data showed similar growth and, using catch per unit effort (CPUE) data from research potting and commercial returns, whether growth rates in this lobster species were affected by population density. Despite the confounded nature of the data, recent growth rates appeared to be lower than in earlier years, growth appeared weakly density-dependent, and the reserve appeared to have a positive effect on lobster growth. The strongest effect was the time period, but the density-dependent and reserve effects appeared real. The reserve effect suggests a negative effect of handling of sublegal-sized lobsters on growth.

scholarly journals Density-dependent growth in ‘catch-and-wait’ fisheries has implications for fisheries management and Marine Protected Areas

AMBIO ◽  
2019 ◽  
Vol 49 (1) ◽  
pp. 107-117 ◽  
Author(s):  
Julian Merder ◽  
Patricia Browne ◽  
Jan A. Freund ◽  
Liam Fullbrook ◽  
Conor Graham ◽  
...  
Keyword(s):  
Fisheries Management ◽  
Marine Protected Areas ◽  
Marine Reserve ◽  
Growth Patterns ◽  
Fundamental Issue ◽  
Catch Per Unit Effort ◽  
Density Dependent ◽  
Negative Effect ◽  
Dependent Growth ◽  
Fisheries Enhancement

Abstract Stock enhancement activities provide an opportunity to examine density-dependent suppression of population biomass which is a fundamental issue for resource management and design of no-take-zones. We document ‘catch-and-wait’ fisheries enhancement where all but the largest lobsters are thrown back, recapturing them later after they have grown to a larger size. The residency, rate of return, and potential negative density-dependent effects of this activity are described using a combination of tagging and v-notching and by relating spatial growth patterns to population density defined with Catch Per Unit Effort. The results successfully demonstrated the concept of catch-and-wait practices. However, a density-dependent suppression of growth (in body size) was observed in male lobsters. This demonstrates a mechanism to explain differences in lobster sizes previously observed across EU fishing grounds with different stock densities. This negative effect of density could also affect individual biomass production in marine reserve or no-take zones.

scholarly journals Factors affecting relative abundance of low-mobility fishing resources: spiny lobster in the Galapagos Marine Reserve

PeerJ ◽  
2019 ◽  
Vol 7 ◽  
pp. e7278 ◽  
Author(s):  
Juan Carlos Murillo-Posada ◽  
Silvia Salas ◽  
Iván Velázquez-Abunader
Keyword(s):  
Monitoring System ◽  
Relative Abundance ◽  
Spatial Scales ◽  
Marine Reserve ◽  
Spiny Lobster ◽  
Fishing Effort ◽  
Additive Models ◽  
Catch Per Unit Effort ◽  
Monthly Basis ◽  
Galapagos Marine Reserve

Management of low-mobility or benthic fisheries is a difficult task because variation in the spatial distribution and population dynamics of the resources make the monitoring and assessment of these fisheries challenging. We assumed that environmental, spatial, and temporal factors can contribute to the variability of the relative abundance of such species; we used Generalized Additive Models for Location Scale and Shape (GAMLSS) to test this hypothesis using as a case study the lobster fishery (targeting two species) in the Galapagos Marine Reserve, Ecuador. We gathered data on each of the two species of lobster on a monthly basis over seven years, including: (a) onboard observers’ records of catch data, fishing effort, and ground location by trip, and (b) data from interviews undertaken with fishers at their arrival to port, recording the same type of information as obtained from onboard observers. We use this information to analyze the effect of the measured variables and to standardize the Catch per Unit Effort (CPUE) in each case, using the GAMLSS. For both species, the temperature, region, fishing schedule, month, distance, and the monitoring system were significant variables of the selected models associated with the variability of the catch rate. ForPanulirus penicillatus, CPUE was higher at night than during the day, and forPanulirus gracilisit was higher during the day. Increased temperature resulted in a decrease of CPUE values. It was evident that temporal, spatial scales and monitoring system can influence the variability of this indicator. We contend that the identification of drivers of change of relative abundance in low-mobility species can help to support the development of monitoring and assessment programs for this type of fisheries.

scholarly journals EFECT OF FOREIGN EXCHANGE RATE FLUCTUATIONS ON NIGERIAN ECONOMY

10.26458/1814 ◽  
2018 ◽  
Vol 18 (1) ◽  
pp. 105-122
Author(s):  
Lawrence Olisaemeka UFOEZE ◽  
Camilus OKUMA, N. ◽  
Clem NWAKOBY ◽  
Udoka Bernard Alajekwu
Keyword(s):  
Economic Growth ◽  
Exchange Rate ◽  
Money Supply ◽  
Significant Positive Effect ◽  
Exchange Rate Fluctuations ◽  
Fixed Exchange Rate ◽  
Oil Revenue ◽  
Time Period ◽  
Negative Effect ◽  
Positive Effect

This study investigated the effect of exchange rate fluctuations on Nigerian economy. The fixed and floating exchange eras were compared to know the exchange rate system in which the economy has fairly better. The time period covered was 1970 to 2012. The study employed the ordinary least square (OLS) multiple regression technique for the analysis. The coefficient of determination (R2), F-test, t-test, beta and Durbin-Watson were used in the interpretation of the results. The resulted revealed that about 85% of the changes in macroeconomic indicators are explained in the fixed exchange era. In the floating exchange era, 99% was explained while the whole periods has 73% explanatory power, hence the floating exchange era (1986 to date) is more effective in explaining economic trend in Nigeria. Also, exchange rate has significant positive effect on GDP during the fixed exchange rate era and negative effect the eras floating and all-time; inflation has insignificant negative effect on GDP during the fixed exchange era; significant effect in floating era and significant negative effect in the all-time period; money supply has insignificant negative effect GDP in fixed exchange era; and significant positive effect during the floating and all-time period; and oil revenue has significant positive effect on the GDP in all the exchange rate regimes (floating, fixed and all-time) in Nigeria.  The study thus conclude that exchange rate movement is a good indicator for monitoring Nigerian economic growth. So far exchange rate has always been a key economic indicator for Nigeria. The floating exchange period has outperformed the fixed exchange rate in terms of contribution inflation, money supply and oil revenue to economic growth. This indicate that the floating exchange rate has been a better economic regime for sustainable economic growth in Nigeria. From the findings, it is evident that oil revenue has positive effect in Nigeria and has remained the mainstay of the economy. It is thus recommended among other things that a positive exchange rate stock should be monitored regularly, so as not to allow those that find exchange rate as an avenue of investment like banks and public carry out their business, which is more devastating to the economy. 

scholarly journals Growth and Income Inequality: A Comparative Analysis

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Ayla Ogus Binatli
Keyword(s):  
Comparative Analysis ◽  
Income Inequality ◽  
Time Period ◽  
Negative Effect ◽  
Time Periods ◽  
Growth Changes ◽  
Changes Over Time ◽  
The Relationship ◽  
Positive Effect ◽  
Over Time

This paper investigates whether the relationship between income inequality and growth changes over time. Two time periods, covering 1970–1985 and 1985–1999, are analyzed and compared. A statistically significant relationship between inequality and growth in either time period fails to emerge. However, there are indications that effect of inequality on growth may be different in the nineties when compared to the seventies. In the literature, a consistent negative effect of inequality on growth is documented although the significance of the effect is open to debate. This paper also finds a negative effect of income inequality on growth in the seventies but, although statistically insignificant, a consistently positive effect in the nineties.

Reevaluating evidence of density-dependent growth in northern fur seals (Callorhinus ursinus) based on measurements of archived skeletal specimens

2004 ◽  
Vol 61 (9) ◽  
pp. 1616-1626 ◽  
Author(s):  
Michael A Etnier
Keyword(s):  
Growth Rates ◽  
Environmental Conditions ◽  
Somatic Growth ◽  
Callorhinus Ursinus ◽  
Density Dependent ◽  
Fur Seals ◽  
Time Period ◽  
Northern Fur Seals ◽  
Time Periods ◽  
Dependent Growth

Analysis of length-at-age measurements of archived skeletal material shows that somatic growth rates of male northern fur seals (Callorhinus ursinus) vary inversely with population density. Von Bertalanffy growth curves were estimated for two series of known-age mandibles collected 1911–1920 (n = 156) and 1940–1953 (n = 151), time periods representing the historic population minimum and maximum, respectively. Mandibles from the former time period are larger than mandibles from the latter time period, suggesting a density-dependent response in somatic growth. Although density-dependent growth in northern fur seals has been suggested before, previous studies have been hampered by the potentially confounding factors of fisheries interactions, variable environmental conditions, and harvest of adult female northern fur seals. The material analyzed here pre-dates the substantial development of the Bering Sea groundfish fishery and the period of heaviest culling of females. Likewise, the two time periods examined are characterized by broadly similar climatic and environmental conditions. Therefore, the results support the hypothesis that measurements of somatic growth rates provide an index of population levels relative to carrying capacity. Growth rate studies could therefore be used to evaluate the current population status of northern fur seals.

The Regime Debate Revisted: A Sensitivity Analysis of Democracy's Economic Effect

2004 ◽  
Vol 34 (4) ◽  
pp. 635-655 ◽  
Author(s):  
JONATHAN KRIECKHAUS
Keyword(s):  
Sensitivity Analysis ◽  
Statistical Significance ◽  
Economic Effect ◽  
Sensitivity Analyses ◽  
Control Variables ◽  
Time Period ◽  
Negative Effect ◽  
The 1960S ◽  
Positive Effect ◽  
Effect On Growth

Some studies find that democracy inhibits growth while other studies find that democracy facilitates growth. Which conclusion is correct? To help resolve this debate, a variety of sensitivity analyses is conducted to answer two basic questions. First, why has the literature yielded contradictory results? Secondly, how believable are these results? The existing contradictions can be explained by analysts' choice of time period, with democracy having a negative effect on growth in the 1960s, a positive effect in the 1980s and no effect at all in the 1970s and 1990s. More generally, however, it is shown here that the statistical significance of these findings varies radically depending upon which control variables one utilizes and how one measures both growth and democracy.

scholarly journals WHO COMES AND WHY? DETERMINANTS OF IMMIGRANTS SKILL LEVEL IN THE EARLY XXTH CENTURY US

2015 ◽  
Vol 81 (1) ◽  
pp. 115-155 ◽  
Author(s):  
Matías Covarrubias ◽  
Jeanne Lafortune ◽  
José Tessada
Keyword(s):  
United States ◽  
The United States ◽  
Economic Incentives ◽  
Skill Level ◽  
Time Period ◽  
Negative Effect ◽  
And Migration ◽  
Migration Costs ◽  
The Impact ◽  
Positive Effect

Abstract:This paper first elaborates a model of intermediate selection where potential migrants must have both the resources to finance the migration cost (liquidity constraint restriction) and an income gain of migrating (economic incentives restriction). We then test the predictions of the model regarding the impact of output in the sending country and migration costs on average skill level of immigrants to the United States from 1899 to 1932, where immigration was initially unrestricted by law and then highly limited. Our panel of 39 countries includes data on occupations that immigrants had in their country of origin, providing a more accurate skill measure than previously available datasets. We find that migration costs have a negative but skill-neutral effect on quantity of immigrants and an increase in output, measured as GDP per capita, has a positive effect on quantity and a negative effect on average skill level of immigrants, suggesting that the main channel by which changes in output affected the average skill level of migrants in that time period is through the easing or tightening of the liquidity constraints and not through the economic incentives as in previous models. Also, using migrants’ occupation in the United States as a measure of skills would lead to misleading conclusions.

Lobster in a bottle: a novel technique for observing the predation of juvenile spiny lobster (Jasus edwardsii)

2016 ◽  
Vol 67 (11) ◽  
pp. 1625 ◽  
Author(s):  
Jan Hesse ◽  
Jenni A. Stanley ◽  
Andrew G. Jeffs
Keyword(s):  
Spiny Lobster ◽  
Video Recording ◽  
Infrared Light ◽  
Night Time ◽  
Novel Approach ◽  
Time Period ◽  
Jasus Edwardsii ◽  
Long Time ◽  
Conger Eel ◽  
The Impact

Determining the impact of predators on juvenile spiny lobsters living on reefs is important for understanding recruitment processes that ultimately help determine the size of economically important lobster populations. The present study describes a novel approach for observing attempted predation on live juvenile spiny lobster (Jasus edwardsii) in situ, by presenting the lobster in a transparent container that was lit with infrared light to enable continuous monitoring, even at night, by video recording. This technique can be used to provide valuable information on overall relative predation pressure from comparative locations and habitats, as well as identify potential predators, their mode of predation, and the timing of their of predation activity. For example, predation attempts on juvenile J. edwardsii by the spotted wrasse (Notolabrus celidotus) were recorded only from 0500 to 1400 hours (daytime) and from 1900 to 2100 hours (dusk), whereas the activity by the northern conger eel (Conger wilsoni) was observed only for the period between 2100 and 0200 hours (nocturnal). This method of assessing predation of juvenile lobsters provides considerable advantages over previously used tethering methods, by allowing continuous observations over a long time period (≥24h), including night time, while also eliminating experimental mortality of juvenile lobsters.

scholarly journals Bayesian depletion model estimates of spiny lobster abundance at two marine protected areas in Belize with or without in-season recruitment

2014 ◽  
Vol 72 (suppl_1) ◽  
pp. i232-i243 ◽  
Author(s):  
Elizabeth A. Babcock ◽  
William J. Harford ◽  
Robin Coleman ◽  
Janet Gibson ◽  
Julio Maaz ◽  
...  
Keyword(s):  
Protected Areas ◽  
Marine Protected Areas ◽  
Marine Reserve ◽  
Spiny Lobster ◽  
Fishing Mortality ◽  
Catch Per Unit Effort ◽  
Strombus Gigas ◽  
Queen Conch ◽  
Opening And Closing ◽  
Typical Model

Abstract In Belize, beginning in 2011 at Glover's Reef Marine Reserve, and in 2012 at Port Honduras Marine Reserve, fishers have been required to keep logbooks to document their catch and effort. A Bayesian depletion model including in-season recruitment was applied to the standardized catch per unit effort (cpue) of Caribbean spiny lobster (Panulirus argus) from the logbooks to estimate the abundance and fishing mortality of lobsters at both sites. Two alternative subsets of the cpue data were used to account for changes in targeting caused by the opening and closing of the queen conch (Strombus gigas) season. At Glover's Reef, a typical model estimated abundance ∼66–79 000 lobsters. Of these, ∼60–85% were present at the beginning of the season and the rest recruited into the fished population later in the season. The depletion model applied to data from the 2012 season at Port Honduras found an abundance of ∼12 000 lobsters, and in-season recruitment was not supported by the data. That in-season recruitment was present at Glover's Reef and not at Port Honduras may be explained by the fact that Glover's Reef has more unfished areas that could serve as a source of adult lobsters during the season. Glover's Reef has a larger no-take zone (20% of the reserve area, compared with 5% at Port Honduras), and it is surrounded by a deep wall reef where lobsters are found below the depth accessible to fishers. The models estimated a harvest fraction of ∼70% in both reserves.

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