Thursday 03 December 2009
The 2009 Seamounts Cruise Blog
Monday 02 November 2009
Reception and Good-Bye Comoros
After a successful completion of the cruise, we have arrived back in the Comoros, this time at Anjouan Island (Nzwani). The day has been busy with a reception of local and national heads of government, local heads of commerce, UNDP and ASCLME delegates as well as the press. After the welcomes, meetings and speeches on the island, the group joined the Research vessel for a tour of the ship and a closer inspection of the equipment, work and samples that have kept the scientists busy for the past month. As a big surprise to everyone, the president of the Union of the Comoros, his excellency Mr Ahmed Abdallah M. Sambialso also graced us with his presence. The atmosphere was congenial and many discussions were held.Now, the time has come to conclude this cruise. Most of us will leave the vessel tomorrow morning and scatter back to our places of origin to work up and start analysing the miriad of collected samples. After that the Dr Fridjof Nansen will continue on to La Reunion ... to start a new collaborative cruise (with the IUCN) on seamounts.
Zooplankton distribution (some results)
Preliminary results suggest that mesozooplankton biomass was highly variable throughout the survey and ranged from 11 to 94 mg /m^3. Total zooplankton wetmass was highest south-east of the Comoros and lowest south west of the islands (see below). Spatially this pattern coincided closely with the position of a cyclonic and anti-cyclonic eddie in the vicinity of 
the Comoros.
the Comoros.As in previous cruises in the region, the horizontal (geographical) distribution of zooplankton suggests that warm-core eddies contain overall very little zooplankton when compared to cold-core eddies and frontal boundary regions. While this result needs to be reinvestigated once updated altimetry data is available, current data suggest that zooplankton biomass increases drastically outside of the warm-core eddies.
The predominant taxa in the smaller size fractions from most stations were:
280μm – 500μm: copepods (also some gastropods, ostracods and amphipods)
500μm – 1mm: copepods (also some amphipods, ostracods and euphausiid nauplii)
1mm – 2mm: small euphausiids and chaetognaths (also some large copepods, amphipods, decapods)
280μm – 500μm: copepods (also some gastropods, ostracods and amphipods)
500μm – 1mm: copepods (also some amphipods, ostracods and euphausiid nauplii)
1mm – 2mm: small euphausiids and chaetognaths (also some large copepods, amphipods, decapods)
The larger size fractions were more variable in composition, with euphausids, decapods, fish larvae and gelatinous zooplankton making up the bulk of the biomass. These larger size fractions of the zooplankton tended to make up a large proportion of the total biomass only during night-time stations.
Further and more detailed analysis of the multinet samples and the 180um Bongo samples is still outstanding and cannot yet be commented on.
Saturday 31 October 2009
Juvenile stages of coastal fish (some results)
With all the surface trawls having been completed, we have had a preliminary look at some of our data on juvenile fish stages. During a total of 19 trawls, some 151 taxa were distinguished, photographed and prepared for bar-coding and identification. The taxa ranged from species with potential commercial importance such as scombrids (2 or 3 tuna species), anchovies and carangids (10 kingfish species) to coral reef inhabitants such as parrot fish, rock cods and surgeon fishes. To get an idea of the variety of forms and colours, click on the image below. Any guessed on the species in question? Some are easier to associate to their families than others. If you get it right, we will let you know once identification has been completed.
In terms of juvenile species richness (number of species), distribution and abundance the current cruise data must be interpreted with great care. The number of trawls was relatively low and no attempts have yet been made to link our sample compositions to the physical environment. In order to strengthen the data, samples from previous ASCLME cruises as well as upcoming regional cruises need to be added to the analysis. Nonetheless some patterns do seem to emerge (but for now, need to be treated with a pinch or salt).
The number of species caught in each trawl did not vary dramatically between locations (see below). On average 21 species were distinguished per trawl. The fact that this is only a tiny fraction of the total number of species identified, suggests that we have either seriously under sampled (likely) or that different species are found in different localities (apparently true in some cases). Only a more complete analysis of all data sets will allow for a less subjective interpretation.
While the number of taxa collected show little variation between locations, the number of individuals per unit water volume vary more dramatically (see below). The highest densities of juveniles were generally caught along the Madagasi shelf, with fewer being observed in the Comoros region and the lowest overall abundances along the Mozambique coast. Again, additional samples need to be added to this analysis to see whether this pattern stands up to scrutiny.
The juveniles caught during this cruise will add to a regional juvenile identification guide, will allow us to better understand larval and juvenile origins and dispersal (with the help of genetics) and should eventually allow for more informed regional management strategies (pertaining to commercial fisheries as well as coastal ecosystem health).
Cruise Progress: 30 October 2009
We are now on our last transect off the Mozambique Coast and are slowly making our way back to the Comoros. The past ten days have kept everyone on board occupied with continuous physical, chemical and biological sampling. Since the beginning of the cruise, some 136 CTD and 46 full biological stations have been completed. In addition, one demersal, three mesopelagic and 16 surface trawls were undertaken (see map for CTD stations).
As we are slowly coming towards the end of this cruise, data is being transcribed, the first analyses are being conducted and reports are being prepared. We hope to be able to present at least some preliminary findings before we leave the ship next week.
Wednesday 21 October 2009
Cruise progress: 19 October 2009
As of yesterday 19th October, transects 10, 3 and 2 have been completed (see also map, blog entry 9-Oct-2009)! Due to some delays with national research permits, more time that anticipated was initially spent in the close vicinity of the Comoros islands. Nonetheless, since then, the first three transects have been completed and we are now on our way back to the islands while undertaking stations on transect 3. To date, physical, chemical and chlorophyll measurements have been obtained at some 39 stations and full environmental stations (incl. zooplankton and phytoplankton collection) at 19 locations. Additionally, one demersal trawl was carried out south of Grande Comore and a total of 12 surface and meso-pelagic trawls.
With the exception of some rough weather and swell after rounding the northern tip of Madagascar, conditions for sampling have so far been favourable. During the latter transect, multi-net deployments were deemed too risky.
With the exception of some rough weather and swell after rounding the northern tip of Madagascar, conditions for sampling have so far been favourable. During the latter transect, multi-net deployments were deemed too risky.
Monday 19 October 2009
The sound of (sound) waves: What is fisheries acoustics?
Fisheries acoustics rely on the physics of sound travelling through water to quantify the distribution of biota in the water column. By sending a signal of a given frequency through the water column and recording the time of travel and the strength of the reflected signal, it is possible to determine the size and location of fish and estimate biomass from the acoustic backscatter. The intensity of the returning echo is a measure of the target strength of a given individual at a particular sound frequency. As a fisheries assessment tool, fisheries acoustics technology is an efficient, non-intrusive method of mapping the water column at a very fine spatial and temporal resolution. It provides a practical alternative to bottom and mid-water trawls. However, validation of fish targets is an essential part of interpreting the acoustic signal for any given location. Output from acoustic surveys can be mapped in relation to bottom habitat type, bathymetry, temperature, time of day etc. The ability to census aquatic organisms are more difficult in deep water as many fish species here lack a swimbladder – the major acoustic reflector in most shelf species.
In its most direct form, we could say that fisheries acoustic produces relative information on size distribution of targets, numbers of organisms in the water column, and estimates of biomass, based on the physical properties of sound traveling through water. However, there are many factors that limit the confidence with which this information can be interpreted into accurate measures of absolute numbers of fish, fish lengths and total biomass.
In its most direct form, we could say that fisheries acoustic produces relative information on size distribution of targets, numbers of organisms in the water column, and estimates of biomass, based on the physical properties of sound traveling through water. However, there are many factors that limit the confidence with which this information can be interpreted into accurate measures of absolute numbers of fish, fish lengths and total biomass.
Acoustic surveys onboard Dr Fridtjof Nansen
Dr Fridtjof Nansen uses ER-60 echo sounders (with ER-60 software) and LSSS (“Large scale survey system”, also called “El-triple-S”) for scrutinizing of echoes. The acoustic transducer is attached to an adjustable keel that can be lowered in rough weather to avoid the damping effect of bubbles. Echo intensities per nautical mile are integrated continuously, and mean values per 1 nautical mile are recorded for mapping and further calculations. The echograms, with their corresponding sA-values, are scrutinized every day. Contributions from the seabed, false echoes, and noise are deleted.
The acoustic survey has been carried out by zigzagging between 50 and 500 meters bottom depth around the Islands, as well as along all the transects (north-south, west-east and oblique transects). Four frequencies are being used (18, 38, 120 and 200 kHz). The survey will target firstly plankton, mesopelagic fish and pelagic fish aggregates. Secondly, the dynamics of the migrating scattering layer and the pelagic layer communities will also be studied in more detail using fisheries acoustic and multinet trawling.
The corrected values for integrated echo intensity are allocated to species according to the trace pattern of the echograms and the composition of the trawl catches. Data from pelagic trawl hauls and bottom trawl hauls considered representative for the pelagic component of the stocks, which is measured acoustically, will be included in the stock abundance calculations.
The echo sounders are watched continuously, and trawl hauls in addition to the predetermined hauls are carried out whenever the recordings change their characteristics and/or the need for biological data makes it necessary. Trawling is thus carried out both for identification purposes and to obtain biological observations, i.e., length, weight, maturity stage, stomach data, and age.
So far the R/V Dr Fridtjof Nansen has undertaken acoustics transects around the 3 Island of the Comoros and Mayotte to determine the distribution and abundance of small pelagic fish shoals. Mid-water trawls have been used on fish aggregations to determine species and size composition. However, very few pelagic shoals have been recorded. Schools of fish have been observed in the surface a couple of times, and we have tried to catch them by rod fishing, but so far with little success. These fish aggregations have not been recorded acoustically either. The reason for this could either be that they are too close to the surface (the echo-sounder can only record fish deeper than 6 m depth, or that the fish swim fast and/or actively avoid the research vessel. Strong scatters of mesopelagic fish have been recorded, but no schools which resemble commercially important species.The conclusion is that there are very few fish in this area. We keep an eye on the echo-sounder all the time and we will conduct pelagic trawling whenever we see any acoustic signals that are strong enough to suggest higher fish abundance.
author: Katherine Michalsen (Norwegian cruise leader); image: Pascal Cotel.
We also made a post about Acoustic Surveys last year with some other details - take a look at this post on acoustic surveys.
We also made a post about Acoustic Surveys last year with some other details - take a look at this post on acoustic surveys.
Trainees and participants continued ...
Soifa Ahamed Soilihi, I am a former student of the University of Tuléar, Madagascar. After my Master's degree I became Conservationist Agent in the non-governmental organization A.I.D.E (Association of Intervention for the Development and the Environment) in the Comoros. I am the national focal point for Coral reef monitoring. After training in the taxonomy of Holothuridae in the Royal Museum of Central Africa (MRAC) in Belgium, I am now in charge of the research unit for Holothuridae, at the mini laboratory of marine biology of INRAPE with the cooperation of the conservatory of the CNDRS museum in the Comoros.
During this ASCLME cruise, I have gotten a big passion for the marine environment, its biodiversity and the importance of every category: the phytoplankton, zooplankton, fishes and finally the big marine mammals. The necessity of having many researchers in the marine environment is a priority for every country and much more for us the island countries.
My passion, led me to resume my studies and to move towards scientific research of marine environments. I followed two Oceanographic training courses, at MARE (Cape Town) organized by the ASCLME project and at ORI (Durban) organized by the SWIOFP project. Now, I would like to proceed with longer term research projects.
During this ASCLME cruise, I have gotten a big passion for the marine environment, its biodiversity and the importance of every category: the phytoplankton, zooplankton, fishes and finally the big marine mammals. The necessity of having many researchers in the marine environment is a priority for every country and much more for us the island countries.
My passion, led me to resume my studies and to move towards scientific research of marine environments. I followed two Oceanographic training courses, at MARE (Cape Town) organized by the ASCLME project and at ORI (Durban) organized by the SWIOFP project. Now, I would like to proceed with longer term research projects.
Life onboard the Nansen provides comfort and a productive work environment within a well established and respected program. Every day, the work becomes more familiar and routine. We are working with a focused enthusiasm which one rarely encounters on land. I hope that the ASCLME project will continue to be a key to open opportunities for research on the marine environment for all the countries in this region.
Nicolas Rascle completed his PhD in Brest, France, on the drift of m
aterials at the ocean surface. He then moved to the University of Cape Town 10 months ago to undertake a postdoctoral research on general ocean circulation and its link to the earth’s climate. His research interests include all the physical properties of the ocean near the surface: the temperature, the salinity, the turbulence, the waves… Passionate about diving and spear-fishing, this cruise is also an opportunity for him to gain experience in biological oceanography and fisheries related research. And, as soon as the captain authorizes it, to put on the snorkel and look at what is going on down there.
aterials at the ocean surface. He then moved to the University of Cape Town 10 months ago to undertake a postdoctoral research on general ocean circulation and its link to the earth’s climate. His research interests include all the physical properties of the ocean near the surface: the temperature, the salinity, the turbulence, the waves… Passionate about diving and spear-fishing, this cruise is also an opportunity for him to gain experience in biological oceanography and fisheries related research. And, as soon as the captain authorizes it, to put on the snorkel and look at what is going on down there.Friday 16 October 2009
Trainees and participants continued ...
Jaffar Mouh
iddine has a MSc in oceanography, is a teacher and research scientist at the Ministry of Education of Anjouan, Comoros. He is also a member of the national center for scientific documentation and research (CNDRS) of Anjouan. In 2004, he was part of his first cruise, conducting research on the Coelacanth. He attended the ASCLME and SWIOFP training course in South Africa in June / July 2009 because he wants to undertake a PhD thesis on Comoran fisheries. This cruise will give him a lot of experience on the fishes and on the general food web of Comoran waters. He also hopes to be part of the identification and treatment of the samples taken during this cruise, which could help him with his research. Presently, the Comoros are lacking knowledge on fish identification and on fisheries management. He would thus like to gain experience among experienced scientist in South Africa and transfer knowledge back to the young university of the Comoros. E-mail address: jaffar_mouhhidine@yahoo.fr
iddine has a MSc in oceanography, is a teacher and research scientist at the Ministry of Education of Anjouan, Comoros. He is also a member of the national center for scientific documentation and research (CNDRS) of Anjouan. In 2004, he was part of his first cruise, conducting research on the Coelacanth. He attended the ASCLME and SWIOFP training course in South Africa in June / July 2009 because he wants to undertake a PhD thesis on Comoran fisheries. This cruise will give him a lot of experience on the fishes and on the general food web of Comoran waters. He also hopes to be part of the identification and treatment of the samples taken during this cruise, which could help him with his research. Presently, the Comoros are lacking knowledge on fish identification and on fisheries management. He would thus like to gain experience among experienced scientist in South Africa and transfer knowledge back to the young university of the Comoros. E-mail address: jaffar_mouhhidine@yahoo.fr Kate 
Munnik is a MSc student at the University of Cape Town, South Africa. Her MSc project is focusing on the movement of inshore line fisheries on the west coast of Southern Africa from the Northern Benguela to the Southern Benguela region. Kate’s research interests include physical oceanography, ichthyology and marine biology. This is her first research cruise and she is very excited to learn about all the different sampling procedures across the disciplines. Personally, she enjoys running in the mountains, sushi, rowing, reading and hockey (in no particular order).
Munnik is a MSc student at the University of Cape Town, South Africa. Her MSc project is focusing on the movement of inshore line fisheries on the west coast of Southern Africa from the Northern Benguela to the Southern Benguela region. Kate’s research interests include physical oceanography, ichthyology and marine biology. This is her first research cruise and she is very excited to learn about all the different sampling procedures across the disciplines. Personally, she enjoys running in the mountains, sushi, rowing, reading and hockey (in no particular order).Wednesday 14 October 2009
Trainees and participants continued ...
Soafia Binty Ali is based at the Institut Haleutique et des Science
s Marines (IH-SM), University of Toliara, Madagascar. She completed her DEA (Masters) on identification and distribution (through space and time) of zooplankton that exist in the Toliara Bay. For the preparation of her PhD, she is concentrating on zooplankton biomass in the Toliara Bay. This is the first time that she will be participating in a research cruise therefore it is very important for her because she has the opportunity to see different materials that is not available in her institute. In addition, she is gaining experience in different methodologies. This cruise will help her collect data and will assist her in the comparison of zooplankton between Madagascar and Comoros. She would like to participate in the analysis of the zooplankton samples collected during this cruise. In her free time she enjoys reading, watching movies and playing handball.
Caren George is an intern based at SA
EON Egagasini node (offshore) and is awaiting her final results from her MSc. Her project centered on the physical, chemical and biological interactions along the STC to the south of Africa. Her research interests include physical oceanography, biological oceanography and fisheries management. She is in the process of developing a PhD topic which she hopes to start next year. She is very excited to join this cruise and gain experience in fisheries related sampling and participating in an international and multi-cultural research cruise. In her spare time, Caren enjoys relaxing at the beach, rock climbing and yoga.
s Marines (IH-SM), University of Toliara, Madagascar. She completed her DEA (Masters) on identification and distribution (through space and time) of zooplankton that exist in the Toliara Bay. For the preparation of her PhD, she is concentrating on zooplankton biomass in the Toliara Bay. This is the first time that she will be participating in a research cruise therefore it is very important for her because she has the opportunity to see different materials that is not available in her institute. In addition, she is gaining experience in different methodologies. This cruise will help her collect data and will assist her in the comparison of zooplankton between Madagascar and Comoros. She would like to participate in the analysis of the zooplankton samples collected during this cruise. In her free time she enjoys reading, watching movies and playing handball.Caren George is an intern based at SA
EON Egagasini node (offshore) and is awaiting her final results from her MSc. Her project centered on the physical, chemical and biological interactions along the STC to the south of Africa. Her research interests include physical oceanography, biological oceanography and fisheries management. She is in the process of developing a PhD topic which she hopes to start next year. She is very excited to join this cruise and gain experience in fisheries related sampling and participating in an international and multi-cultural research cruise. In her spare time, Caren enjoys relaxing at the beach, rock climbing and yoga.
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