A Climate for Change

(^156) The Fishing and Mariculture Industries Human Development Report - Croatia 2008
Other categories of biological responses to climate
have been observed:

• Changes in the migration patterns of sprat


• The drastic collapse of the European anchovy
  stock since 1995


• Mass mortalities of round sardinella were record-
  ed along the Apulian and central Croatian coasts
  in January 2002, when an abrupt fall in seawater
  temperature occurred.^20 This fish is a warm water
  species that was recorded for the first time along
  the Croatian coast 40 years ago. As this fish is not
  yet utilised commercially in Croatia, there was no
  commercial impact on the fishing sector. Further-
  more, this event has not affected native species.

9.5.2. Future impacts: temperature changes

Climate change-related warming may have the fol-

lowing implications for the Croatian fishing sector:

• Due to faster biological processes at all levels of
  marine ecosystems, the growth rate of fish should
  be higher and reproduction seasons should be
  longer for most species. As a result, the recruit-
  ment of species that thrive in warm water should
  be significantly better.


• The opposite is likely to occur with species that
  thrive in cold water, such as Norwegian lobster.
  These species will migrate to colder areas, either
  horizontally (moving north, south, east or west)
  or vertically (moving to deeper levels).


• Temperature increases will heighten the risk of ox-
  ygen level decrease and depletion in shallow areas
  of the Adriatic. This situation will create conditions
  that allow for the increase of species that tolerate
  warm water and lower oxygen levels.


• The introduction of new disease organisms or ex-
  otic or undesired species is likely to occur due to
  increased sea temperatures.

Tuna, which is the most important economic product

within the fishery and mariculture sector, is a typical

warm water species. Tuna farming, as currently prac-

ticed in the Eastern Adriatic, will probably benefit

from global warming due to higher growth rates re-

sulting from more intensive feeding and a higher feed

conversion index.

Certain positive impacts may occur, such as the in-

creased potential for aquaculture, in general. The

warmer seawater temperature in the winter, as a con-

sequence of expected climate change, might create

favourable conditions for the growth of marine organ-

isms during this season. Therefore, rearing time could

be shorter and aquaculture production could become

more efficient. This applies in particular to two spe-

cies: gilthead sea breamX and the Mediterranean mus-

sel.XI These two species are better adapted to higher

temperatures, and will benefit from a rise in Adriatic

water temperatures. The only potential problem re-

lates to the reproduction period of the mussel, during

which the species needs freshwater inflow – inflow

that could be limited due to lower precipitation lev-

els in the area. This will be especially important during

the summer months, when precipitation levels on the

coast are expected to drop – perhaps up to 39.3% in

the summer months in Dalmatia (See Chapter 2).

The situation with two other species – sea bassXII and

the European oysterXIII - is different, as they generally

prefer colder water. Experiences from Greece and Tur-

key can be applied to future conditions on the Croa-

tian coastline, as their sea bass farming has decreased

due to warmer water and associated disease suscepti-

bility.^21 Presently, sea bass culture in the Eastern Adri-

atic is among the best in the Mediterranean, due to

excellent water conditions that include lower temper-

atures. Temperature increases in the Adriatic will no

doubt result in a necessary shift to growing gilthead

sea bream, a species tolerant to higher temperatures.

Alternatively, the cages with sea bass may have to be

moved to colder zones or deeper nets, up to 10 metres

in depth, may need to be used. This would substan-

tially increase the costs of sea bass production.

Positive impacts

may occur, such

as the increased

potential for

aquaculture, in

general

X Sparus aurata

XI Mytilus galloprovinciallis

XII Dicentrarchus labrax

XIII Ostrea edulis