26 
PACIFIC SCIENCE, VoL VIII, January, 1954 
among the species in the area and differential 
flotation among the species killed. These last 
two factors are impossible to evaluate, and 
the best that can be done is to point out their 
possible effects. 
Death of these fishes may have been brought 
about by one or more of four causes: (1) the 
fishes may have been killed by simple over- 
heating; (2) the lava entering the water may 
have introduced some directly or indirectly 
lethal chemical; (3) fishes with an air bladder 
may have been carried upward so rapidly by 
the upwelling water as to have caused over- 
expansion of this organ; and (4) the under- 
water explosions, caused by the breaking out 
of the molten lava from the conduits, may 
have caused some mortality. We do not have 
evidence that would make profitable a dis- 
cussion of any of these possible causes of 
death. With any of them, however, it would 
seem likely that large fishes would be better 
able than smaller ones to move out of the 
way in time to avoid harm. The differential 
in decimation between large and small fishes 
may have been increased by the possibility 
that the water moving in to replace that which 
had upwelled carried with it small, weak 
swimmers from the surrounding region into 
the outbreak area. 
Concerning the possibility of differential 
flotation, our only evidence is from the spec- 
imens we collected. With regard to these, two 
questions arise. What brought them to the 
surface, and, once there, why did they not 
sink back to the bottom? As to the first, one 
might suspect that the water heated by the 
lava would make its way through the water 
column above it to the surface, where it would 
spread out as a thin layer. Under such a 
hypothesis only the fishes from the area 
around the outbreaks would be brought to 
the top. Actually our collections contain epi- 
pelagic and a large number of bathypelagic 
fishes, as well as bottom forms. The presence 
of these pelagic species can best be explained 
by hypothesizing considerable mixing be- 
tween the rising water and that around it. 
It does seem apparent that, regardless of the 
amount of mixing, fishes with a high specific 
gravity would be less readily transported to 
the surface than those with lighter bodies. 
Likewise, among fishes with -the same spec- 
ific gravity, those with a higher surface- 
volume ratio, e.g., small fishes, would be 
more easily carried in the upwelling water 
than those with a lower surface- volume ratio. 
It is possible, however, that not all the fishes 
we collected were originally brought to the 
surface by upwelled water, but rather that 
some of them were forced up after death by 
gases of decomposition. 
This possibility leads into the question of 
why fishes were at the surface when we got 
there. Evidence from some of our specimens 
indicates that their air bladders became over- 
expanded and remained so after death, serving 
as floats. However, others show no expansion 
of an air bladder, and a large number of our 
specimens presumably do not even possess 
this organ. The presence of such fishes at the 
surface can best be explained by hypothesiz- 
ing the formation of gases in parts of the body 
other than the air bladder. For example, the 
two brotulids we took on June 6 had the 
belly (but not the air bladder) greatly dis- 
tended and empty. Most of our specimens, 
however, showed no abdominal distension. 
Whether decomposition gases and air bladder 
expansion can explain the presence of all our 
fishes at the surface seems open to question. 
Whatever the full explanation is, it must take 
into account the fact that, with the exception 
of two jellyfishes, we found no organisms 
other than fishes at the surface. 
Our four collections together probably to- 
tal 300 to 500 specimens distributed among 
more than 20 families. Perhaps a third of the 
individuals are myctophids. Except for the 
Myctophidae, and to a lesser extent the Ster- 
noptychidae, none of the families is repre- 
sented by more than a few specimens. Among 
groups unrepresented in our collections are 
sharks, flatfishes, and angler fishes. 
In number of species our material would 
