These are the lecture notes from the first lecture of my Marine Ecology course (BIOL 462) at UNC last fall.  I dumped Blackboard and just started using WordPress to share lectures with my students.  It works pretty well, but moving all my lecture content from PowerPoint to WP was a pain (especially for my TA).  Benefits include greater ease in incorporating multi-media and outside resources via links and no need for students to download massive PDF or ppt files.  And you can also share lectures with the world!  Speaking of digital teaching resources for marine ecology, check this out.

Required readings for this lecture: Two articles on declining tuna (here and here and go here if you don’t know anything about bluefin tuna). Also, as supplemental reading, take  a look at some of the other stories on fishing at SeaMonster here.

Changing perceptions about our impact on the sea


Global declines in marine fisheries (from Myers and Worm 2003)

  • Industrial fisheries typically reduce community biomass within 15 years of exploitation
  • Large predatory fish biomass is only about 10% of pre-industrial levels
  • Management based on recent data alone can be misleading
  • Population baselines are probably much higher than we assumed

Overfishing of shark populations (from Baum et al. 2003)

  • Some species have declined 75% over the last 15 years
  • Caused by both bycatch and directed fisheries
  • All recorded species except 1 has declined by 50%
  • Sharks have a very low intrinsic rate of population increase
  • Many species are at risk for large scale extinction

Big, long-lived and valuable

From this paper.  Read more about the IUCN red list here and here.

One criticism of the IUCN evaluation process and of the study findings is (from here):

Their concerns focus on the IUCN’s “rate of decline” criterion. This compares the rate at which a population is decreasing to the age at which individuals in the population reach sexual maturity (between 5 and 20 years for tunas).  The team describes two cases where uncritical application of the rate-of-decline criterion could lead to misleading threat assessments for tunas and billfishes. One is when a population maintains a low but steady level following an earlier precipitous drop due to overfishing. Uncritical application of the rate-of-decline criterion in this case would underestimate threat by placing the population in the “least concern” category, when it may well be vulnerable to extinction in the long term due to genetic effects and natural fluctuations.

The second case would overestimate the threat to a population. This could occur if the IUCN rate-of-decline criterion were applied to a previously un-fished or “virgin” stock that had been quickly culled to a level matching its “maximum sustainable yield” — the goal of fishery managers attempting to ensure the largest on-going harvest.  Rapid depletion of a population to its maximum sustainable yield — typically 40-50% of the virgin stock for tunas — would place it in the vulnerable category on the IUCN Red List, directly contradicting a fishery manager’s view that this is a well-managed and sustainable fishery.

Ode to the Stellers Sea Cow

Now on to bluefin tuna

Note NOAA recently declined to designate bluefin tuna as “endangered” under the US ESA (go here).

Bluefin landings, from the NOAA bluefin tuna fact sheet (here)


Back to shifting baselines   note the live links to the video about this, just click on the picture!


note the live links to the audio about this, just click on the picture!

The Impact of Recreational Fisheries (from Coleman et al. 2004)

  • Study contradicts previous estimates of recreational catch (2%)
  • Used NMFS and other databases
  • Compared catch of “populations of concern” = those populations listed by NMFS as overfished
  • For some important and overfished species, recreational catch was greater than commercial catch:
  • Red snapper in the Gulf of Mexico: 59%
  • Red drum in the South Atlantic: 93%
  • Recreational fishery is focused on higer trophic levels
  • link to NPR story here

MSY see here and here for background and read about carrying capacity and logistic growth on the EoE.



5 Responses to “Overfishing”

  1. John Wares says:

    So do you use this format for lecturing? As in, just scrolling through a days lecture via the web? At some point I think we have to move beyond powerpoint, it is actually kind of restrictive. If you’ve looked at Gore’s “Our Choice” on the iPad you can see there are some really amazing formats for presenting ideas, they just aren’t necessarily in our hands yet.

  2. Nan says:

    This is great! They recently decided to cut Marine Ecology here at San Diego State for the upcoming spring semester, so reading over these notes filled an empty void 🙂

  3. John Bruno says:

    Hi Nan, wow! talk to the profs that teach it – bet they rescheduled for another semester???

    JW: I do just scroll down via the web – we have wireless in the classroom. It can be a little clunky scrolling but it is easier to move back to content. I live using lots of short videos and this works so well for that and gives the students access to them. There are also so many great links to papers, blog posts etc. Why anyone would use a text book in 2012 is totally unclear. Web notes are free to students, and they is nothing to print or download. The class is paperless, with the exception of exams and I hope to change that too.

    I was never able to embed video, etc into power point well and if the content is online, I find linking to it from PP in the middle of a lecture awk.

    Ill try the Our Choice. I was thinking of doing my benthics 2012 talks using a blog post!

  4. Chris Petrone says:


    I like to think that I have my finger on the pulse of educational technology, but the idea of teaching through a continuous blog has never come across my radar. Well done! This allows you to embed all sorts of material and is accessible to students whenever and wherever they have an internet connection.

    Until e-textbooks like Gore’s Our Choice (which looks amazing) are streamlined and ubiquitous, transitional methods, like what you are doing, are helping to advance students’ education and the digital learning experience.

    Again, well done!

    • John Bruno says:

      Thanks Chris. I also hope it is more akin to the way they usually get information (the web) than the way we scientists like to give it to them (textbooks and powerpoint). Being able to embed readings (PDFs from journal articles) and links to blogs and other online content, side by side worked out really well. I used to have separate portals in blackboard for PDFs, links, etc, which sucked.

      This works especially well for me, because I add very little text into PPT slides (either in lectures or talks). If I say it, I don’t put it in as text. Doing so seems redundant and distracting to me. Besides, this way the students still have to come to the lecture. I write a lot on the board including words, graphs and conceptual diagrams. I use the content in the blog as supporting material.

      Clare and I kind of petered out near the end of the semester in doing this, only because it took so much time. But I have about half the class migrated to wordpress and I will move over the rest in time for next fall:)

      Any ideas about how to improve this are more than welcome! I do want to use twitter next year to communicate with students and may start doing pod casts again (weekly reviews of materials).

Leave a Reply