Science corner: latest fish & fisheries research

[FishStyx]

Like everything else, it's not what ONE individual can do, but the cumulative efforts of millions of ONE's.... this is what, in my opinion, humans still have to realize... gotta learn from bees and ants...

Environmental degradation is rarely caused by the actions of one individual (well, except oil spills and similar)... as a society we need to waste less, recycle/re-use/reduce more. Have less babies and stop thinking about today... every single planning exercise is done on a 4/5 year basis... nature does not operate like that!

Brilliantly put! 

[icstuff]

John I really enjoyed these posts on the research about the Lichia amia.

I assume that they are classified as sub species, but is it still possible for the populations to interbreed?
And is it known if individuals travel between the  two areas?

[John F]

At this stage they're still considered as part of the same species (despite biological and genetic differences). Just separate stocks or sub-populations diverging slowly... eventually they will evolve into 2 whole different species.

The genetics study mentioned above, found a highly genetic divergence and isolation between the two stocks which means they don't interbreed mainly due to physical barriers - the authors cite the oceanographic features of the Benguela current (doesn't necessarily mean they can't! I supposed if you put them together in a tank they would?).   

[John F]

It's quite an interesting species actually... was reading a bit more about it....

A study done in 2008 (Smith, 2008) concluded that the (then) current stock was only at 14% of its unfished level!!!

This study also analyzed tagging data from the ORI database. of the 6456 fish tagged only 457 had been recaptured (7%)!

Only 16% (71) of the re-captured fish were re-released!

These fish migrate along the KZN-Cape-KZN coast but not a single fish tagged in the Cape area has been reported in Angola (no surprises there! ).


Reference (PDF available)
Smith, D. (2008). Movement, growth and stock assessment of the coastal fish Lichia amia (Teleostei: Carangidae) off the South African coast.  MSc thesis, 164 pp. Durban, University of KwaZulu-Natal, School of Life & Environmental Sciences.

[icstuff]

thank you

[PH]

How many legs does an octopus have?
Extract from the book " The Second Book Of General Ignorance" by John Lloyd and John Mitchenson

Two.
Octopuses have eight limbs protruding from their bodies, but recent research into how they use them has redefined what they should be called. They use their back two tentacles to propel themselves along the seabed, leaving the remaining six to be used for feeding. As a result, marine biologists now tend to refer to them as animals with two legs and six arms.

[FishStyx]

How many legs does an octopus have?
Extract from the book " The Second Book Of General Ignorance" by John Lloyd and John Mitchenson

Two.
Octopuses have eight limbs protruding from their bodies, but recent research into how they use them has redefined what they should be called. They use their back two tentacles to propel themselves along the seabed, leaving the remaining six to be used for feeding. As a result, marine biologists now tend to refer to them as animals with two legs and six arms.

It's such an awesome book. It was based on the BBC TV program QI also by John Loyd but with Stephen Fry as host. It's a good and interesting laugh.

[John F]

Surveys of white sharks (Carcharodon carcharias) off bathing beaches in Algoa Bay, South Africa

* The study provides information on the existence of a possible inshore nursery area for white sharks (Carcharodon carcharias) in Algoa Bay, South Africa.

* In total, 43 flights were conducted, using a Robinson R22 helicopter, between October 2010 and March 2012.

* A total of 50 white sharks was sighted, with a maximum sighting rate of seven sharks per hour in October 2010.

* The majority (96.0%) of sharks observed were less than 2.5m in length, immature and sighted between October and March (98.0%).

* Modelling showed that water temperature and barometric pressure explained the sightings of sharks, peaking in mid-December.

* A total of 58 white shark catches was recorded from key informant interviews with shore anglers between July 2009 and December 2011.

* Sharks ranged in size from 1.5 to 2.5m in total length, with young-of-the-year sharks (,1.75 m) accounting for 69.0% of the catch.

* Defining key habitats for young-of-the-year and juveniles is critical for the management and conservation of white sharks worldwide.


PDF available. Those interested please send me a PM.

Reference
Dicken, M. L. & A. J. Booth (2013). Surveys of white sharks (Carcharodon carcharias) off bathing beaches in Algoa Bay, South Africa. Marine and Freshwater Research, 64: 530-539.

[icstuff]

Just shows you the importance of the ban on GW fishing in SA, there are many of them but not of breeding age.

[Marthin]

Which also means they are only now after 20 years starting to effectively breed as well!

[John F]

A review of the Oceanographic Research Institute’s Cooperative Fish Tagging Project: 27 years down the line

* The Oceanographic Research Institute’s (ORI) Cooperative Fish Tagging Project was initiated in 1984 and is one of the most enduring and successful environmental projects of its kind in South Africa.

* By the end of 2011, 5 130 anglers had joined the project, of whom 3 457 had tagged one or more fish.

* In the project’s 27-year history (1984–2011), over 251 900 fish from 368 different species have been tagged and released, of which approximately 13 192 (5.2%) have been recaptured.

* The five most commonly tagged species to date are galjoen, dusky kob, dusky shark, garrick/leervis and spotted
grunter.

* Information from the Tagging Project has been extensively used in numerous research projects, scientific publications, popular articles and postgraduate theses.

* The results generated by this project have also contributed to policy development and decision-making on linefish management in South Africa.

* Furthermore, the project has had a positive impact on improving angler awareness and knowledge about linefish resources. The concept of tag and release has partly been responsible for changing the ethics of the recreational fishing community, many of whom now release their catch, thereby contributing to a more sustainable fishing future.


PDF available. Those interested please let me know.


Reference:
Dunlop, S. W., B. Q. Mann & R. P. van der Elst (2013). A review of the Oceanographic Research Institute’s Cooperative Fish Tagging Project: 27 years down the line. African Journal of Marine Science, 35(2): 209-221.

[John F]

The effects of barotrauma on five species of South African line-caught fish

* Management measures for South African line-caught fish include output controls such as closed seasons, bag
and size limits and no-take moratoria.

* The main condition for these measures to be effective is that undesirable catches can be successfully released.

* However, most of the line-caught fish species are susceptible to barotrauma, a condition caused in physoclists [fishes with closed swimbladders] by the rapid reduction of hydrostatic pressure during the ascent to the surface
during capture.

* The effects of barotrauma on five commercially important species were investigated: roman, silver kob, hottentot, santer and carpenter.

* A classification of the external signs of barotrauma was developed and internal and external signs of barotrauma were examined in relation to fishing depth and fish size, and compared between species.

* Immediate post-release mortality was investigated during a catch-and-release experiment.

* Medium-term survival of roman (~1 d) was examined by returning fish to depth in cages and subsequent monitoring on SCUBA.

* Results indicate that most of the fish experience barotrauma even when caught at relatively shallow depths.

* External signs include extension of the inflated, everted stomach through the mouth, distended eyes, protrusion of the hind-gut and other organs through the cloaca, and gas bubbles in the dermal tissue between the fin rays.

* The absence of any obvious external signs of barotrauma can be misleading as dissections of such fish revealed ruptures of the swimbladder and other internal injuries consistent with barotrauma.

* Results indicate that there might be significant post-release mortality, a factor that needs to be taken into account during stock assessment predictions and during the implementation of catch restrictions.



PDF available. Those interested please let me know.

Reference:
Kerwath, S. E., C. G. Wilke & A. Götz (2013). The effects of barotrauma on five species of South African line-caught fish. African Journal of Marine Science, 35(2): 243-252.

[John F]

Can fish really feel pain?

* The paper reviews studies claiming that fish feel pain;

* Deficiencies in the methods used for pain identification were found, particularly for distinguishing unconscious detection of injurious stimuli (nociception) from conscious pain;

* Results were also frequently misinterpreted and not replicable, so claims that fish feel pain remain unsubstantiated;

* Comparable problems exist in studies of invertebrates;

* In contrast, an extensive literature involving surgeries with fishes shows normal feeding and activity immediately or soon after surgery.

* C fiber nociceptors, the most prevalent type in mammals and responsible for excruciating pain in humans, are rare in teleosts and absent in elasmobranchs studied to date;

* A-delta nociceptors, not yet found in elasmobranchs, but relatively common in teleosts, likely serve rapid, less noxious injury signaling, triggering escape and avoidance responses;

* Clearly, fishes have survived well without the full range of nociception typical of humans or other mammals, a circumstance according well with the absence of the specialized cortical regions necessary for pain in humans;

* Recent claims for consciousness in fishes are evaluated, but found to lack adequate supporting evidence, neurological   feasibility, or the likelihood that consciousness would be adaptive;

* Even if fishes were conscious, it is unwarranted to assume that they possess a human-like capacity for pain;

* Overall, the behavioral and neurobiological evidence reviewed shows fish responses to nociceptive stimuli are limited and fishes are unlikely to experience pain.


PDF available. Those interested please let me know.

Reference:
Rose, J. D., R. Arlinghaus, S. J. Cooke, B. K. Diggles, W. Sawynok, E. D.   Stevens, & C. D. L. Wynne (2014). Can fish really feel pain? Fish and Fisheries, 15:97-133.

[REEFMAN]

Fascinating articles Marcos!! Keep 'em coming! 

[Gregf]

Hi Marcos

May I have a copy of the barotrauma article please. Thank you for this thread, top of the range.

 

[John F]

Thanks, guys. Hope they are somehow helpful.

@Greg, email sent.

[John F]

Changing relative abundance and behaviour of silky and grey reef sharks baited over 12 years on a Red Sea reef

* There is a lack of studies on how provisioning may influence shark numbers and behaviour.

* The effects of long-term provisioning were investigated at a Red Sea reef, where both grey reef shark and silky shark  occurred.

* Initially, grey reef sharks outnumbered silky sharks, but over 6 years, silky shark numbers increased almost 20-fold, whereas grey-reef sightings decreased >90%.

* Following this, silky-shark sightings also declined considerably (>80%).

* It is suggested that these declines could relate to local overfishing.

* Sighting records indicated that provisioning extended the residency of transient individuals.

* Conversely, the site fidelity typical of grey reef sharks would have made them more susceptible to local depletion. Silky sharks were recorded as behaving more boldly when present in greater numbers, but the decline in grey reef sharks appears to be unrelated to the initial increase in the numbers of silky shark.


PDF available.

Reference:
Clarke, C. R., J. S. E. Lea & R. F. G. Ormond (2013). Changing   relative abundance and behaviour of silky and grey reef sharks baited   over 12 years on a Red Sea reef. Marine and Freshwater Research, 64:   909-919.

[John F]

Agricultural impact on the pelagic ecosystem of the small temporarily open/closed Seteni Estuary, South Africa

* The catchment of the Seteni Estuary, a small intermittently open estuary in South Africa, has been under extensive sugar cultivation for over 60 years.

* The study aimed to determine the impact of agriculturally derived nutrients on its pelagic communities.

* The main effects, thus far, being evident in the exceptionally high nitrogen concentrations and imbalance in nutrient ratios.

* Despite this, the system remains largely functional.

* There is potential for deterioration should the catchment become more nutrient-rich through poor management or land-use changes.


PDF available.

Referrence:
Carrasco, N. K. , R. Perissinotto & A. Whitehead (2013). Agricultural impact on the pelagic ecosystem of the small temporarily open/closed Seteni Estuary, South Africa. Marine and Freshwater Research, 64: 938-950.

[RobinF]

  Marcos.

I cannot even put into words how important this info is. (As in all the posts you've made here). Very well done. Please continue, it is great to read this.

Cheers
Robin

[icstuff]

Thank you for a very informative thread!
Do these articles come from one journal?