Prey preference and the consumption of sea urchins and juvenile abalone by captive rock lobsters (Jasus lalandii )

2001 ◽  
Vol 52 (5) ◽  
pp. 773 ◽  
Author(s):  
S. Mayfield ◽  
E. de Beer ◽  
G. M. Branch
Keyword(s):  
South African ◽  
Laboratory Experiments ◽  
Carapace Length ◽  
Consumption Rate ◽  
Prey Species ◽  
Sea Urchins ◽  
Fishing Ground ◽  
Field Observations ◽  
Rock Lobster ◽  
Fishing Area

Recent studies on the diet of the South African rock lobster (Jasus lalandii) have shown an increase in the consumption of sea urchins in certain areas relative to earlier assessments. Concurrent ecological surveys have demonstrated the dependence of juvenile abalone on urchins for their survival, and a radical increase in the abundance of lobsters in the area that is the main abalone fishing ground. This paper describes laboratory experiments on the consumption of urchins by lobsters, and the preferences for different prey species. Small lobsters (<68 mm carapace length) ate no urchins. Larger lobsters ate urchins of all sizes, although small urchins were preferred. The consumption rate was easily sufficient for the lobsters to have caused the documented disappearance of urchins (and juvenile abalone) in the main abalone fishing area. Lobsters showed a strong preference for mussels over all other prey offered, and for juvenile abalone over urchins, although previous field observations and laboratory experiments have shown that urchins provide shelter for juvenile abalone. However, if black mussels were available in addition to sea urchins and juvenile abalone, consumption of sea urchins and juvenile abalone declined.

Interrelations among rock lobsters, sea urchins, and juvenile abalone: implications for community management

2000 ◽  
Vol 57 (11) ◽  
pp. 2175-2185 ◽  
Author(s):  
Stephen Mayfield ◽  
George M Branch
Keyword(s):  
South African ◽  
Laboratory Experiments ◽  
Sea Urchins ◽  
Ecosystem Approach ◽  
Community Management ◽  
Rock Lobster ◽  
Negative Effects ◽  
Major Threat ◽  
Complex Interactions ◽  
The Relationship

Field and laboratory experiments demonstrate that juveniles of South African abalone (Haliotis midae) depend vitally on the protection from predation that they gain from living concealed beneath Cape urchins (Parechinus angulosus). Recent reports suggest that rock lobsters (Jasus lalandii) have increased substantially in the region where the commercial abalone fishery is centered. This increase has been blamed for a recorded collapse of urchin populations and dramatic reductions in the numbers of juvenile abalone. We verified the substantial increase in rock lobster abundance there. Surveys covering 200 km of coastline showed that densities of urchins were negatively correlated with those of large lobsters (>68 mm carapace length) and that densities of juvenile abalone were positively correlated with those of urchins. The indirect negative effects of rock lobsters on juvenile abalone clearly pose a major threat to the abalone industry, already under stress from poaching. Quantification of the relationship between juvenile abalone and urchins and between urchins and rock lobsters allows a forecast of the magnitude of lobster harvesting necessary to reduce them to a level at which urchins may recover and sustain juvenile abalone. The complex interactions involved emphasize the importance of an ecosystem approach for the management of these stocks.

Movements of the western rock lobster (Panulirus cygnus) within shallow coastal waters using acoustic telemetry

2008 ◽  
Vol 59 (7) ◽  
pp. 603 ◽  
Author(s):  
L. D. MacArthur ◽  
R. C. Babcock ◽  
G. A. Hyndes
Keyword(s):  
Coastal Waters ◽  
Small Proportion ◽  
Acoustic Telemetry ◽  
Large Scale ◽  
Laboratory Experiments ◽  
Movement Patterns ◽  
Field Observations ◽  
Rock Lobster ◽  
Panulirus Cygnus ◽  
Shallow Coastal Waters

Understanding the residency and movement patterns of major consumers, such as lobsters, in coastal waters is important for the management of coastal habitats and their fisheries. In the present study, we tagged 34 Panulirus cygnus with acoustic transmitters on a shallow coastal reef in south-western Australia and monitored their movements using fixed and manual receivers between November and May 2005–2006 and 2006–2007. We determined the proportion of ‘white’ (migratory-phase) lobsters emigrating from the reef between November and January and also characterised the large-scale movements of ‘red’ (residential-phase) and white lobsters. We undertook tank experiments to determine the effect of tagging and handling on P. cygnus behaviour. Counter to our expectation, 50% of white lobsters were detected on the reef after the migration period, whereas only a small proportion (13.6%) of white lobsters were tracked leaving the reef and only one individual displayed directional offshore movement. This limited movement indicates that coastal no-take zones may build up legal-sized 4–5+ year old lobsters because many of these are likely to remain resident over the migration season. Laboratory experiments and field observations suggest that tagging and handling affect lobster behaviour and movement for a few days post tagging, potentially confounding conclusions on dispersal and movement patterns in some studies.

scholarly journals Hydraulic transmissivity inferred from ice-sheet relaxation following Greenland supraglacial lake drainages

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ching-Yao Lai ◽  
Laura A. Stevens ◽  
Danielle L. Chase ◽  
Timothy T. Creyts ◽  
Mark D. Behn ◽  
...  
Keyword(s):  
Laboratory Experiments ◽  
Ice Sheet ◽  
Drainage System ◽  
Greenland Ice Sheet ◽  
Field Observations ◽  
Surface Uplift ◽  
Drainage Networks ◽  
Order Of Magnitude ◽  
Lake Drainage ◽  
Magnitude Increase

AbstractSurface meltwater reaching the base of the Greenland Ice Sheet transits through drainage networks, modulating the flow of the ice sheet. Dye and gas-tracing studies conducted in the western margin sector of the ice sheet have directly observed drainage efficiency to evolve seasonally along the drainage pathway. However, the local evolution of drainage systems further inland, where ice thicknesses exceed 1000 m, remains largely unknown. Here, we infer drainage system transmissivity based on surface uplift relaxation following rapid lake drainage events. Combining field observations of five lake drainage events with a mathematical model and laboratory experiments, we show that the surface uplift decreases exponentially with time, as the water in the blister formed beneath the drained lake permeates through the subglacial drainage system. This deflation obeys a universal relaxation law with a timescale that reveals hydraulic transmissivity and indicates a two-order-of-magnitude increase in subglacial transmissivity (from 0.8 ± 0.3 $${\rm{m}}{{\rm{m}}}^{3}$$ m m 3 to 215 ± 90.2 $${\rm{m}}{{\rm{m}}}^{3}$$ m m 3 ) as the melt season progresses, suggesting significant changes in basal hydrology beneath the lakes driven by seasonal meltwater input.

Using a GLMM to estimate the somatic growth rate trend for male South African west coast rock lobster, Jasus lalandii

2004 ◽  
Vol 70 (2-3) ◽  
pp. 339-349 ◽  
Author(s):  
A. Brandão ◽  
D.S. Butterworth ◽  
S.J. Johnston ◽  
J.P. Glazer
Keyword(s):  
Growth Rate ◽  
South African ◽  
West Coast ◽  
Somatic Growth ◽  
Rock Lobster ◽  
Somatic Growth Rate

Planktivory by alewife (Alosa pseudoharengus) and rainbow smelt (Osmerus mordax) on microcrustacean zooplankton and dreissenid (Bivalvia: Dreissenidae) veligers in southern Lake Ontario

1995 ◽  
Vol 52 (5) ◽  
pp. 925-935 ◽  
Author(s):  
Edward L. Mills ◽  
Connie Adams ◽  
Robert O'Gorman ◽  
Randall W. Owens ◽  
Edward F. Roseman
Keyword(s):  
Laboratory Experiments ◽  
Lake Ontario ◽  
Osmerus Mordax ◽  
Field Observations ◽  
Alosa Pseudoharengus ◽  
Rainbow Smelt ◽  
Consumption Rates ◽  
South Shore ◽  
Young Of The Year ◽  
Veliger Larvae

The objective of this study was to describe the diet of young-of-the-year and adult alewife (Alosa pseudoharengus) and rainbow smelt (Osmerus mordax) in nearshore waters coincident with the colonization of Lake Ontario by Dreissena. Laboratory experiments and field observations indicated that alewife and rainbow smelt consumed dreissenid veligers and that the veligers remained intact and identifiable in the digestive tract for several hours. Dreissenid larvae were found in field-caught alewife and rainbow smelt in August 1992, even though veliger densities were low (<0.1/L). Zooplankton dominated the diet of all fish and veliger larvae were <0.1% of the biomass of prey eaten by these fish. Density of veligers and the distribution of settled dreissenids declined from west to east along the south shore of Lake Ontario. Based on veliger consumption rates we measured and the abundance of veligers and planktivores, we conclude that planktivory by alewife and smelt in the nearshore waters of Lake Ontario did not substantially reduce the number of veligers during 1991–1993. However, our results indicate that if the density of veligers in Lake Ontario decreases, and if planktivores remain abundant, planktivory on veliger populations could be significant.

scholarly journals Identifikasi Gosong Karang Mengggunakan Citra Satelit Sentinel 2A (Studi Kasus: Perairan Pesisir Nias Utara)

2020 ◽  
Vol 21 (1) ◽  
pp. 95-108
Author(s):  
Anang Dwi Purwanto ◽  
Teguh Prayogo ◽  
Sartono Marpaung
Keyword(s):  
Coral Reefs ◽  
Image Classification ◽  
Classification Method ◽  
Fishing Ground ◽  
Field Observations ◽  
Geometric Correction ◽  
Radiometric Correction ◽  
Object Based ◽  
Sentinel 2A ◽  
North Sumatra

ABSTRACTThe waters of Northern Nias, North Sumatra Province have a great potential for natural resources, one of which is the reef which is often used as a fishing ground. This study aims to identify and monitor the distribution of coral reefs around the waters of Northern Nias. The location of study is limited by coordinates 97° 0'31'' - 97° 16'54'' E and 1° 29'2'' LU - 1° 6'24'' N. The study locations were grouped in 6 (six) areas including Mardika reef, Wunga reef, Mausi1 reef, Mausi2 reef, Tureloto reef and Senau reef. The data used were Sentinel 2A imagery acquisition on 19 September 2018 and field observations made on 6-12 September 2018. Data processing includes geometric correction, radiometric correction, water column correction and classification using pixel-based and object-based methods as well as by delineating on the image. One classification method will be chosen that is most suitable for the location of the reef. The results show Sentinel 2A was very helpful in mapping the distribution of coral reefs compared to direct observation in the field. The use of image classification method rightly is very helpful in distinguishing coral reef objects from surrounding objects. The estimated area of coral reefs was 1,793.20 ha with details of the Mardika reef 143.27 ha, Wunga reef 627.06 ha, Mausi1 reef 299.84 ha, Mausi2 reef 141.873 ha, Tureloto reef 244.73 ha, Senau reef 336.44 ha. The existence of coral reefs have a high potential as a fishing ground and a natural tourist attraction.Keywords: coral reefs, sentinel 2A, lyzenga 1978, image classification, Northern NiasABSTRAKPerairan Nias Utara yang terletak di Provinsi Sumatra Utara memiliki potensi kekayaan alam yang besar dimana salah satunya adalah gosong karang yang sering dijadikan lokasi penangkapan ikan oleh nelayan. Penelitian ini bertujuan untuk mengidentifikasi dan monitoring sebaran gosong karang di sekitar perairan Nias Utara. Lokasi penelitian dibatasi dengan koordinat 97°0’31’’ - 97°16’54’’ BT dan 1°29’2’’LU – 1°6’24’’  LU. Untuk mempermudah dalam pengolahan data maka lokasi kajian dikelompokkan dalam 6 (enam) kawasan diantaranya gosong Mardika, gosong Wunga, gosong Mausi1, gosong Mausi2, gosong Tureloto dan gosong Senau. Data yang digunakan adalah citra satelit Sentinel 2A hasil perekaman tanggal 19 September 2018 dan hasil pengamatan lapangan yang telah dilakukan pada tanggal 6 - 12 September 2018. Pengolahan data meliputi koreksi geometrik, koreksi radiometrik, koreksi kolom air dan klasifikasi menggunakan metode klasifikasi berbasis piksel dan berbasis objek serta deliniasi citra. Dari ketiga metode klasifikasi tersebut akan dipilih satu metode klasifikasi yang sesuai dengan lokasi gosong karang. Hasil penelitian menunjukkan citra Sentinel 2A sangat membantu dalam memetakan sebaran gosong karang dibandingkan dengan pengamatan langsung di lapangan. Pemilihan metode klasifikasi citra satelit yang tepat sangat membantu dalam membedakan objek gosong karang dengan objek di sekitarnya. Estimasi total luasan gosong karang di perairan Nias Utara adalah 1,793.20 ha dengan rincian luasan gosong karang Mardika 143.27 ha, gosong Wunga 627.06 ha, gosong Mausi1 299.84 ha, gosong Mausi2 141.873 ha, gosong Tureloto 244.73 ha, gosong Senau 336.44 ha. Keberadaan gosong karang memiliki potensi yang tinggi sebagai lokasi penangkapan ikan dan memiliki daya tarik sebagai tempat wisata alam.Kata kunci: gosong karang, sentinel 2A, lyzenga 1978, klasifikasi citra, Nias Utara

scholarly journals A sink host allows a specialist herbivore to persist in a seasonal source

2021 ◽  
Vol 288 (1958) ◽  
pp. 20211604
Author(s):  
Alicja Laska ◽  
Sara Magalhães ◽  
Mariusz Lewandowski ◽  
Ewa Puchalska ◽  
Kamila Karpicka-Ignatowska ◽  
...  
Keyword(s):  
Experimental Evolution ◽  
Laboratory Experiments ◽  
Field Observations ◽  
Stepping Stones ◽  
Specialist Herbivore ◽  
Negative Growth Rate ◽  
Evolutionary Rescue ◽  
Main Host ◽  
Negative Growth

In seasonal environments, sinks that are more persistent than sources may serve as temporal stepping stones for specialists. However, this possibility has to our knowledge, not been demonstrated to date, as such environments are thought to select for generalists, and the role of sinks, both in the field and in the laboratory, is difficult to document. Here, we used laboratory experiments to show that herbivorous arthropods associated with seasonally absent main (source) habitats can endure on a suboptimal (sink) host for several generations, albeit with a negative growth rate. Additionally, they dispersed towards this host less often than towards the main host and accepted it less often than the main host. Finally, repeated experimental evolution attempts revealed no adaptation to the suboptimal host. Nevertheless, field observations showed that arthropods are found in suboptimal habitats when the main habitat is unavailable. Together, these results show that evolutionary rescue in the suboptimal habitat is not possible. Instead, the sink habitat functions as a temporal stepping stone, allowing for the persistence of a specialist when the source habitat is gone.

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