Cartoon guide to biodiversity loss XLIII

12 08 2017

I’m travelling again, so here’s another set of fishy cartoons to appeal to your sense of morbid fascination with biodiversity loss in the sea. See full stock of previous ‘Cartoon guide to biodiversity loss’ compendia here.

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Limited nursery replenishment in coral reefs

27 03 2017
Haemulon sciurus

blue-striped grunt (Haemulon sciurus)

Coral reef fishes are wonderfully diverse in size, form, and function, as well as their need for different habitats throughout the life cycle. Some species spend all of their life in the same kind of coral habitat, while others need different places to breed and feed.

Fishes requiring different habitats as they progress through life often have what we call ‘nurseries’ in which adults lay eggs and the subsequent juveniles remain, and these places are often dominated by mangroves or seagrasses (i.e., they are not part of the coral reef).

While we’ve known for quite some time that when these nursery habitats are not around, adjacent coral reefs have few, if any, of these nursery-dependent species. What we haven’t known until now is just how far the influence of nurseries extends along a coral reef.

In other words, if a nursery is present, just how many new recruits do different areas of a reef receive from it? Read the rest of this entry »





World’s greatest conservation tragedy you’ve probably never heard of

13 10 2016

oshiwara_riverI admit that I might be stepping out on a bit of a dodgy limb by claiming ‘greatest’ in the title. That’s a big call, and possibly a rather subjective one at that. Regardless, I think it is one of the great conservation tragedies of the Anthropocene, and few people outside of a very specific discipline of conservation ecology seem to be talking about it.

I’m referring to freshwater biodiversity.

I’m no freshwater biodiversity specialist, but I have dabbled from time to time, and my recent readings all suggest that a major crisis is unfolding just beneath our noses. Unfortunately, most people don’t seem to give a rat’s shit about it.

Sure, we can get people riled by rhino and elephant poaching, trophy hunting, coral reefs dying and tropical deforestation, but few really seem to appreciate that the stakes are arguably higher in most freshwater systems. Read the rest of this entry »





Disadvantages of marine protected areas

29 02 2016

 

 

 

Stop wasting time

Stop wasting time





It’s not always best to be the big fish

3 02 2016

obrien_fish_2Loosely following the theme of last week’s post, it’s now fairly well established that humans tend to pick on the big species first.

From fewer big trees, declines of big carnivores, elephant & rhino poaching, to fishing down the web, big species tend to cop it hardest when it comes to human-caused ecological disturbance.

While there are a lot of different combinations of traits that make some species more vulnerable to extinction than others (see examples for legumes, amphibians, sharks & teleosts, and mammals), one of the main ones is species size.

Generally speaking, larger species tend to produce fewer offspring and breed later in life than smaller species. This means that despite larger species tending to live longer than their smaller counterparts, their ‘slow’ reproductive output means that they are generally more susceptible to rapid environmental change (mainly via human intervention). In other words, their capacity for self-replacement is often too low to counteract the offtake from direct exploitation or habitat loss.

Despite a reasonable scientific understanding of this extinction-risk principle, the degree to which human disturbance affects species’ distributions is much less well quantified, and this is especially true for marine species.

I’m proud to announce another fascinating paper led by my postdoc, Camille Mellin, that has just come out online in Nature CommunicationsHumans and seasonal climate variability threaten large-bodied coral reef fish with small ranges.

With the world’s largest combined dataset of coral reef fish surveys for the entire Indo-Pacific (including the coral reef fish biodiversity hotspot — the Coral Triangle), we examined which conditions best described the distribution of fishes over a range of body sizes. Read the rest of this entry »





Shrinking global range projected for the world’s largest fish

7 08 2013
© W. Osborn (AIMS)

© W. Osborn (AIMS)

My recently finished PhD student, Ana Sequeira, has not only just had a superb paper just accepted in Global Change Biology, she’s recently been offered (and accepted) a postdoctoral position based at the University of Western Australia‘s Oceans Institute (in partnership with AIMS and CSIRO). As any supervisor, I’m certainly pleased when a student completes her PhD, but my pride as an academic papa truly soars when she gets her first job. Well done, Ana. This post by Ana is about her latest paper.

Following our previous whale shark work (see herehereherehere, here, here and here), especially the recent review where we inferred global connectivity and suggest possible pathways for their migration, we have now gone a step further and modelled the habitat suitability for the species at at global scale. This paper sets a nice scene regarding current habitat suitability, which also demonstrates the potential connectivity pathways we hypothesised previously. But the paper goes much further; we extend our predictions to a future scenario for 2070 when water temperatures are expected to increase on average by 2 °C.

Sequeira et al_GCB_Figure 3

Global predictions of current seasonal habitat suitability for whale sharks. Black triangles indicate known aggregation locations. Solid line delineates areas where habitat suitability > 0.1 was predicted.

Regarding the current range of whale sharks (i.e., its currently suitable habitat), we already know that whale sharks span latitudes between about 35 º North to South. We also know that this geographical range has been exceeded on several occasions. What we did not know was whether conditions were suitable enough for whale sharks to cross from the Indian Ocean to the Atlantic Ocean – in other words, whether they could travel between ocean basins south of South Africa. Our global model results demonstrate that suitable habitat in this region does exist at least during the summer, thus supporting our hypotheses regarding global connectivity!

It’s true that the extensive dataset we used (30 years’ worth of whale shark sightings collected by tuna purse seiners in the three major oceans – data provided by the IRD, IOTC and SPC) has many caveats (as do all opportunistically collected data), but we went to great trouble to deal with them in this paper (you can request a copy here or access it directly here). And the overall result: the current global habitat suitability for whale sharks does agree well with current locations of whale shark occurrence, with the exception of the Eastern Pacific for where we did not have enough data to validate. Read the rest of this entry »





Fast-lane mesopredators

29 07 2013

Another post from Alejandro Frid (a modified excerpt from a chapter of his forthcoming book).

I fall in love easy. Must be my Latino upbringing. Whatever it is, I have no choice on the matter. So for five years and counting, I have been passionate about lingcod (Ophiodon elongatus) and rockfish (Sebastes spp.), upper- and mid-level predatory fishes on rocky reefs of the Northeast Pacific.

Lingcod are beautiful and fierce. Rockfish are cosmic. Both taste mighty good and—surprise, surprise—have been overfished to smithereens throughout much of their range. Howe Sound, my field site near Vancouver, British Columbia, is no exception, although new protective legislation might be starting to give them some slack.

Our dive surveys1 and earlier studies, in combination, have pieced together a story of ecosystem change. In the Howe Sound of today, lingcod rarely exceed body lengths of 80 cm. But up to 30 years ago, when overfishing had yet to inflict the full extent of its current damage, lingcod with lengths of 90 to 100 cm had been common in the area. There is nothing unique about this; most fisheries target the biggest individuals, ultimately reducing maximum body size within each species of predatory fish.

As predators shrink, the vibrant tension of predation risk slips away. The mechanism of change has a lot to do with mouth size. Predatory fishes swallow prey whole, usually head or tail first, so it is impossible for them to eat prey bigger than the width and height of their open jaws. And bigger fishes have bigger jaws, which makes them capable not only of consuming larger prey, but also of scaring bigger prey into using antipredator behaviours, such as hiding in rocky crevices. As predators shrink, big prey enter a size refuge and only small prey remain at risk, which can alter trophic cascades and other indirect species interactions. Read the rest of this entry »