Environment: the key to understanding the South African chokka squid (Loligo vulgaris reynaudii) life cycle and fishery?

1994 ◽  
Vol 6 (2) ◽  
pp. 249-258 ◽  
Author(s):  
M.J. Roberts ◽  
W.H.H. Sauer
Keyword(s):  
Life Cycle ◽  
Coastal Upwelling ◽  
Environmental Variability ◽  
Southern Oscillation ◽  
The South ◽  
Enso Events ◽  
Loligo Vulgaris ◽  
Large Fluctuations ◽  
High Turbidity ◽  
Physical And Chemical

This paper explores effects of environmental variability on the life cycle of the chokka squid, Loligo vulgaris reynaudii in South Africa, particularly the effect of physical and chemical influences on adult distribution, and the availability of spawning aggregations to the local jig fishery. The following hypotheses are presented: 1) temperature, dissolved oxygen and currents have a direct effect on the demersal distribution of adult chokka on the feeding grounds, but this is restricted to the west coast where environmental conditions are more extreme relative to the south coast, 2) chokka catches increase in proportion to the extent of coastal upwelling, 3) spawning behavior along the inshore regions (<50m) is strongly influenced by turbidity near the seabed. High turbidity forces the spawning popuation to lay their eggs in deeper waters, and are thus not available to the jig fishery. 4) El Niño – Southern Oscillation (ENSO) events are linked with large fluctuations in the availability of spawning squid aggregations to the inshore jig fishery.

scholarly journals Coastal upwelling along the southwest coast of India – ENSO modulation

2008 ◽  
Vol 26 (6) ◽  
pp. 1331-1334 ◽  
Author(s):  
K. Muni Krishna
Keyword(s):  
Coastal Upwelling ◽  
Southern Oscillation ◽  
Monsoon Season ◽  
Trade Winds ◽  
Southwest Coast Of India ◽  
Southwest Coast ◽  
Enso Events ◽  
The Pacific ◽  
Basin Scale ◽  
Using Data

Abstract. An index of El Niño Southern Oscillation (ENSO) in the Pacific during pre monsoon season is shown to account for a significant part of the variability of coastal Sea Surface Temperature (SST) anomalies measured a few months later within the wind driven southwest coast of India coastal upwelling region 7° N–14° N. This teleconnection is thought to result from an atmospheric bridge between the Pacific and north Indian Oceans, leading to warm (cold) ENSO events being associated with relaxation (intensification) of the Indian trade winds and of the wind-induced coastal upwelling. This ENSO related modulation of the wind-driven coastal upwelling appears to contribute to the connection observed at the basin-scale between ENSO and SST in the Arabian Sea. The ability to use this teleconnection to give warning of large changes in the southwest coast of India coastal upwelling few months in advance is successfully tested using data from 1998 and 1999 ENSO events.

scholarly journals Inter ENSO variability and its influence over the South American monsoon system

2006 ◽  
Vol 6 ◽  
pp. 167-171 ◽  
Author(s):  
A. R. M. Drumond ◽  
T. Ambrizzi
Keyword(s):  
Interannual Variability ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Low Frequency ◽  
Austral Summer ◽  
Phase Changes ◽  
The South ◽  
Enso Variability ◽  
Enso Events

Abstract. Previous studies have discussed the interannual variability of a meridional seesaw of dry and wet conditions over South America (SA) associated to the modulation of the South Atlantic Convergence Zone (SACZ). However, they did not explore if the variability inter ENSO (El Niño Southern Oscillation) can be related to the phase changes of this dipole. To answer this question, an observational work was carried out to explore the atmospheric and Sea Surface Temperature (SST) conditions related to the same ENSO signal and to opposite dipole phases. Rotated Empirical Orthogonal Function (REOF) analysis was applied over normalized Chen precipitation seasonal anomalies in order to find the dipole mode in the Austral Summer (December to February). The fourth rotated mode, explaining 6.6% of the total variance, consists of positive loading over the SACZ region and negative loading over northern Argentina. Extreme events were selected and enhanced activity of SACZ during the Summer season (SACZ+) was identified in nine years: five during La Niña events (LN) and two in El Niño episodes (EN). On the other hand, inhibited manifestations of this system (SACZ-) were identified in seven years: four in EN and two during LN. Power spectrum analysis indicated that the interannual variability of the precipitation dipole seems to be related to the low frequency and to the quasi-biennial part of ENSO variability. The ENSO events with the same signal can present opposite phases for the dipole. The results suggest that the displacement of the convection over Indonesia and western Pacific can play an important role to modulate the seesaw pattern.

Variation in Pacific Hake (Merluccius productus) Summer Length-at-Age Near Southern Vancouver Island and Its Relationship to Fishing and Oceanography

1990 ◽  
Vol 47 (11) ◽  
pp. 2195-2211 ◽  
Author(s):  
Barry D. Smith ◽  
Gordon A. McFarlane ◽  
Mark W. Saunders
Keyword(s):  
Sea Level ◽  
Coastal Upwelling ◽  
Southern Oscillation ◽  
Vancouver Island ◽  
Relative Strength ◽  
Merluccius Productus ◽  
Enso Events ◽  
Sea Level Anomalies ◽  
General Decline ◽  
Level Height

Male and female Pacific hake (Merluccius productus) sampled in summer off southern Vancouver Island since 1976 show a general decline, plus marked variability, in mean lengths-at-age. Multiple regression analysis related the length-at-age pattern to von Bertalanffy and density-dependent growth, length-selective fishing mortalities, and a suite of oceanographic covariates (sea level height, temperature, and salinity anomalies). Because offshore Pacific hake migrate annually between southern California and British Columbia, with larger fish migrating further north, we deduce that the summer fishery in Canadian waters selectively removes the larger hake each year causing a decline over time in mean lengths-at-age. Apart from the general decline, oceanographic factors explained most interannual variability in mean lengths-at-age. Specifically, mean lengths-at-age were generally smaller in years of above normal sea level height and temperature, and below normal salinity. Sea level anomalies in particular have been associated with the relative strength of the alongshore currents within the coastal upwelling domain; thus, we argue that stronger northward (or weaker southward) flows assist the northward migration of hake. Consequently, in years of higher than normal sea level, such as during major El Niño–Southern Oscillation (ENSO) events, more smaller hake arrive off Vancouver Island in summer resulting in lower mean lengths-at-age.

scholarly journals Regional Variability of Surface Ocean Radiocarbon from Southern Great Barrier Reef Corals

Radiocarbon ◽  
1995 ◽  
Vol 37 (2) ◽  
pp. 517-524 ◽  
Author(s):  
Ellen R. M. Druffel ◽  
Sheila Griffin
Keyword(s):  
Dissolved Inorganic Carbon ◽  
Southern Oscillation ◽  
Enso Event ◽  
The South ◽  
Regional Variability ◽  
South Equatorial Current ◽  
Reef Corals ◽  
Surface Ocean ◽  
Enso Events ◽  
Equatorial Current

High-precision ∆14C and stable isotope (∆18O and ∆13C) records are reported for post-bomb corals from three sites off the eastern Australian coast. We observe that ∆14C values increased from ca. −50′ in the early 1950s to +130‰ by 1974, then decreased to 110‰ by 1991. There is general agreement between the coral results and ∆14C of dissolved inorganic carbon (DIC) in seawater measured previously for locations in the South Pacific. ∆14C values at our southern hemisphere sites increased at a slower rate than those observed previously in the northern hemisphere. Small variations in the ∆14C records among our three sites are likely due to differences in circulation between the shallow coastal waters and the open ocean influenced by seasonal upwelling. Low ∆14C is associated with most El Niño/Southern Oscillation (ENSO) events after 1970, indicating input of low 14C waters from the southern-shifted South Equatorial Current. The exception is the severe ENSO event of 1982–1983 when upwelling in the South Equatorial Current could have ceased, causing normal ∆14C values in the corals during this time.

ENVIRONMENTAL VARIABILITY ASSOCIATED WITH EASTERN LITTLE TUNA [Eutynnus affinis (Cantor, 1849)] CATCHES: A CASE FOR THE NORTH INDRAMAYU WATERS, JAVA SEA

2016 ◽  
Vol 78 (4-2) ◽  
Author(s):  
Mega Syamsuddin ◽  
Sunarto Sunarto ◽  
Lintang Yuliadi
Keyword(s):  
Environmental Conditions ◽  
El Niño ◽  
Environmental Variability ◽  
El Nino ◽  
Southern Oscillation ◽  
Ocean Climate ◽  
Enso Events ◽  
The North ◽  
Favorable Environmental Condition ◽  
Java Sea

Environmental variability during El Niño Southern Oscillation (ENSO) derived from satellite imagery of Sea Surface Temperature and Chlorophyll a were investigated during 2010 to 2014. This study investigates how ocean climate variability of ENSO affects environmental conditions and further addresses their relations with Eastern Little Tuna catches. Changes in environmental conditions during ENSO events resulted in perceivable variations in catches, with an average catches of 839.6 t during El Niño. The La Niña event, with an average catches of 602.6 t was less favorable for catches. Major fishing location located around 3.22-6.59ºS and 108.20-109.67ºE could have been suggested as the most favorable environmental condition to Eastern Little Tuna catch in the North Indramayu waters, Java Sea.

Relative contributions of North and South Pacific sea surface temperature anomalies to ENSO

2020 ◽  
Author(s):  
Ruiqiang Ding ◽  
Yu-heng Tseng ◽  
Jianping Li
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Southern Oscillation ◽  
South Pacific ◽  
Sea Surface ◽  
Coupling Mechanism ◽  
The South ◽  
Enso Events ◽  
The North ◽  
Sst Forcing

&lt;p&gt;Variations in the sea surface temperature (SST) field in both the North Pacific [represented by the Victoria mode (VM)] and the South Pacific [represented by the South Pacific Quadrapole (SPQ) mode] are related to the state of the El Ni&amp;#241;o-Southern Oscillation (ENSO) three seasons later. Here, with the aid of observational data and numerical experiments, we demonstrate that both VM and SPQ SST forcing can influence the development of ENSO events through a similar air&amp;#8211;sea coupling mechanism. By comparing ENSO amplitudes induced by the VM and SPQ, as well as the percentages of strong ENSO events followed by the VM and SPQ events, we find that the VM and SPQ make comparable contributions and therefore have similar levels of importance to ENSO. Additional analysis indicates that although VM or SPQ SST forcing alone may serve as a good predictor for ENSO events, it is more effective to consider their combined influence. A prediction model based on both VM and SPQ indices is developed, which is capable of yielding skillful forecasts for ENSO at lead times of three seasons.&lt;/p&gt;

scholarly journals Coastal upwelling along the southwest coast of India – ENSO modulation

2008 ◽  
Vol 5 (1) ◽  
pp. 123-134 ◽  
Author(s):  
K. Muni Krishna ◽  
V. Kovačević ◽  
M. Gačić
Keyword(s):  
Coastal Upwelling ◽  
Southern Oscillation ◽  
Trade Winds ◽  
Southwest Coast Of India ◽  
Southwest Coast ◽  
Enso Events ◽  
The Pacific ◽  
Basin Scale ◽  
Coastal Sea ◽  
Using Data

Abstract. An index of El Niño Southern Oscillation (ENSO) in the Pacific during pre monsoon is shown to account for a significant part of the variability of coastal Sea Surface Temperature (SST) anomalies measured a few months later within the wind driven southwest coast of India coastal upwelling region 7° N–14° N. This teleconnection is thought to result from an atmospheric bridge between the Pacific and north Indian Oceans, leading to warm (cold) ENSO events being associated with relaxation (intensification) of the Indian trade winds and of the wind-induced coastal upwelling. This ENSO related modulation of the wind-driven coastal upwelling appears to contribute to the connection observed at the basin-scale between ENSO and SST in the Arabian Sea. The ability to use this teleconnection to give warning of large changes in the southwest coast of India coastal upwelling few months in advance is successfully tested using data from 1998 and 1999 ENSO events.

scholarly journals Climatic variability related to El Niño in Ecuador − a historical background

2006 ◽  
Vol 6 ◽  
pp. 237-241 ◽  
Author(s):  
K. Arteaga ◽  
P. Tutasi ◽  
R. Jiménez
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Equatorial Region ◽  
Northern Coast ◽  
The South ◽  
Enso Events ◽  
The Past ◽  
El Niño Events ◽  
El Nino Events

Abstract. This paper reports on an investigation into the chronology of El Niño/Southern Oscillation (ENSO) events, during the period from the arrival of conquistadores in Ecuador in 1532 until the year 1900. A number of probable El Niño events and drought years can be dated from anecdotal reports of significant rainfall and drought in the equatorial region. The evidence of ENSO has been documented from early reports in the South America archives. A large number of books and articles have been reviewing from the Ecuadorian archives to obtain information on El Niño events that have occurred over the past centuries. This information is based on evidence obtained from the equatorial region, where strong and very strong El Niño events clearly separate the northern part of the Ecuadorian coast from the southern region, the normally rainy season specially from west-central to the south coast of Ecuador, as well as the drought years, reported in this region which is climatologically and oceanographically different from the moist Northern coast of Ecuador. Given the normal occurrence of rains in the southern coast of Ecuador, it is reasonable to expect that at least some of the major rainy seasons would be recorded in local chronicles and publications. This information has been compared with reports obtained from Peru. Relative strengths of events are based on such considerations as wind and current effects on travel times of ancient sailing ships, degree of physical damage and destruction, amounts of rainfall and flooding, human disease epidemic, mass mortality of endemic marine organism, rises in sea temperatures and sea levels, effects on coastal fisheries. This paper is the first survey of the historical sources concerned the rainfall and drought in Ecuador. In the course of this investigation we also noted some extended periods of time, near decadal or longer over the past records, when the amount and/or strength of El Niño and its resulting effects appeared to represent significant long-term climate changes.

scholarly journals Spatio-temporal associations of albacore CPUEs in the Northeastern Pacific with regional SST and climate environmental variables

2014 ◽  
Vol 71 (7) ◽  
pp. 1717-1727 ◽  
Author(s):  
A. Jason Phillips ◽  
Lorenzo Ciannelli ◽  
Richard D. Brodeur ◽  
William G. Pearcy ◽  
John Childers
Keyword(s):  
North Pacific ◽  
Large Scale ◽  
Environmental Variability ◽  
Southern Oscillation ◽  
Spatial Dynamics ◽  
Catch Per Unit Effort ◽  
Variable Effect ◽  
Positive Effects ◽  
The North ◽  
Additive Mixed Models

Abstract This study investigated the spatial distribution of juvenile North Pacific albacore (Thunnus alalunga) in relation to local environmental variability [i.e. sea surface temperature (SST)], and two large-scale indices of climate variability, [the Pacific Decadal Oscillation (PDO) and the Multivariate El Niño/Southern Oscillation Index (MEI)]. Changes in local and climate variables were correlated with 48 years of albacore troll catch per unit effort (CPUE) in 1° latitude/longitude cells, using threshold Generalized Additive Mixed Models (tGAMMs). Model terms were included to account for non-stationary and spatially variable effects of the intervening covariates on albacore CPUE. Results indicate that SST had a positive and spatially variable effect on albacore CPUE, with increasingly positive effects to the North, while PDO had an overall negative effect. Although albacore CPUE increased with SST both before and after a threshold year of 1986, such effect geographically shifted north after 1986. This is the first study to demonstrate the non-stationary spatial dynamics of albacore tuna, linked with a major shift of the North Pacific. Results imply that if ocean temperatures continue to increase, US west coast fisher communities reliant on commercial albacore fisheries are likely to be negatively affected in the southern areas but positively affected in the northern areas, where current albacore landings are highest.

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