150 | Chapter 8
shelf seas. No deeper than a few hundred metres, penetrated by life-
enhancing sunlight and often nutrient rich, the shelf seas are consis-
tently productive. No wonder they are heavily used by seabirds and fish-
ers alike, especially as the limited depths allow trawling. At the shelf
margin, the shelf break signals the start of the continental slope which
leads downward to the abyssal depths of the ocean where the seabed is
generally 2– 5 km below the sea surface.
The waters above the shelf break are favoured by some species. This
preference is emphasized by the titles of otherwise sober scientific arti-
cles, for example ‘Black Petrels patrol the ocean shelf- break’ and ‘Diet
and feeding ecology of the Royal Albatross Diomedea epomophora – King
of the shelf break and inner slope’.
Although once abundant on ‘mainland’ New Zealand, the stronghold
of the Black Petrel today is Great Barrier Island, a substantial island in
the outer Hauraki Gulf off Auckland. When tracked by GPS,^8 most
chick- feeding petrels hastened north- east for 100– 400 km, only to slow
down when they reached the shelf break in waters 600– 1,000 m deep.
Indeed one bird headed out to the shelf- break (or slope) whereupon it
swept back and forth in 30– 70 km legs more or less parallel to the break.
(See Map 10.) It is very difficult to resist the temptation to interpret this
movement pattern as patrolling the prime feeding zone in an attempt
to detect signs of food. Study leader, Robin Freeman, mused that the
upwellings associated with the break may have generated high produc-
tivity, signalled by high levels of dimethyl sulphide, and thus attracted
the Black Petrels.
Albatrosses breed on some of the world’s remotest islands – but there
are exceptions. One of the most accessible colonies is that on Taiaroa
Head. Lying within the city limits of Dunedin, on the east coast of New
Zealand’s South Island, the Northern Royal Albatross colony is acces-
sible by car as a Sunday afternoon outing. Possibly the thrill of the en-
counter is diminished by the ease of access, just as a helicopter landing
on Mount Everest (if feasible) would lack the exultation of a mountain-
eering ascent.
For obvious disturbance reasons, most visitors are not permitted to
do what the late Mike Imber did, collect pellets regurgitated by the
albatrosses.^9 These pellets are chock- full of deep amber squid beaks, too